Evidence Update: Neutering and Cancer Risk in Dogs

I have written extensively about the risks and benefits of neutering in dogs and cats. This is an area of active research, and new data emerge regularly to challenge existing beliefs and illustrate the amazing complexity of living organisms and he factors that lead to disease. One subject within this larger field concerns the effects of neutering on cancer risk. The data is complex and inconsistent, but there are some trends that emerge from multiple studies of different types in various populations. Some cancers almost certainly occur less often following neutering, and others almost certainly occur more often, and this relationship is heavily influenced by genetics, most clearly manifested as different effects of neutering on cancer risk in different breeds. A new publication has added a bit of evidence to this subject, which provides a good opportunity to review what we know and don’t know.

Grüntzig K, Graf R, Boo G, et al. Swiss Canine Cancer Registry 1955-2008: Occurrence of the Most Common Tumour Diagnoses and Influence of Age, Breed, Body Size, Sex and Neutering Status on Tumour Development. J Comp Pathol. 2016 Aug-Oct;155(2-3):156-70.

This study looked retrospectively at biopsies of both living and deceased dogs included in a cancer registry that has been collecting data since 1955 and compared the results with other information about these dogs, including age, breed, and neutering status. The general findings confirm the results of previous research, showing that cancer risk typically increases with age, that different breeds have different overall cancer risk as well as predisposition to different types of cancer, and that there are exceptions to almost any generalization one can make about cancer in dogs. These are certainly not surprising findings, and they generally confirm the results of other studies.

One finding that was a bit surprising was that mixed-breed dogs did not appear to be at lower overall cancer risk than purebred dogs, which has appeared to be the case in other studies. The difference between the populations studied or the methods used may be responsible for the different findings, but it raises some doubts about the general assumption that purebred dogs are more likely overall to get cancer than mutts.

In terms of cancer risk and neutering, the findings are summarized in the following table. This compares the odds of cancer in neutered and intact animals, separated both by sex (males and females) and also by the method used to detect the cancer (biopsy samples from living animals compared with post-mortem samples from deceased animals). The odds ratio is given, indicating the odds of a particular cancer in the indicated group compared with intact animals of the same sex using the same detection method.

In general, these data confirm the findings of several other studies, though there are differences. Neutering appears to reduce the risk of adenocarcinomas, especially in females. This primarily relates to breast cancer, which occurs much, much more often in intact females than in neutered females or males. Other types of cancer either showed no difference in risk with neutering or appeared to be more common in neutered animals of one or both sexes.

The differences in odds were consistently larger in post-mortem samples. This reflects a source of bias in the data. Samples of testicles and mammary tissue from living animals undergoing surgery are likely commonly submitted, while samples of other types of cancer from other organs are much less likely to be analyzed and submitted to the registry. This influences the numbers of cancers of different types seen, and means that post-mortem submissions are more common for most tumors except breast and testicular tumors, which are more likely to be sampled in animals that are neutered. In any case, the study accounted for this source of bias by separating the data as seen in the table.

gruntzig-table

The best way to identify real trends is to compare data from different studies, often involving different populations (ages, breeds, geographic locations, etc.) and study methods (clinical patients, cancer registry studies, pathology lab studies, insurance company data, etc). I have collected results from various studies comparing risk between neutered and intact males and females for the types of cancer most commonly thought to be influenced by neutering (other than mammary cancer, of course, which is quite clearly less common in neutered females than in intact females). These data show both some patterns suggesting an increase in the risk of several cancers with neutering as well as some inconsistency in the data, indicating this risk varies by breed and sex and possibly other population factors.

Studies involving neutering and osteosarcoma risk.

gruntzig-table-osa

Studies involving neutering and mast cell tumor risk. gruntzig-table-mct

Studies involving neutering and lymphosarcoma risk.

gruntzig-table-lsa

Studies involving neutering and hemangiosarcoma risk.

gruntzig-table-hsa

Posted in Science-Based Veterinary Medicine | 2 Comments

Are Our Dogs Dying Younger Than They Used To?

One of the most popular ways to promote unconventional ideas, including alternative therapies, is through fear. Claiming that health, longevity, and other measures of well-being have declined from some time in the past opens the door to claims that science-based healthcare is ineffective and that we should return to some past practice or adopt something radically different. Dr. Karen Becker, a popular promoter of veterinary pseudoscience, recently made just this sort of argument, claiming that dogs are not living as long as they used to and then implying that this can be blamed  on commercial pet food and “toxins,” by which her past writing indicates she means vaccines, parasite prevention products, and pretty much any conventional medical treatment.

To demonstrate this, she cites two surveys of pet owners conducted by the U.K. Kennel Club, one in 2004 and another in 2014.

Why Are These Popular Dogs Dying So Much Younger Than They Used To?

The 2014 survey also found that tragically, the average lifespan of a pedigree dog in the U.K. is just 10 years. In a 2004 Kennel Club report, the average was 11 years, 3 months.

This means the median longevity of Britain’s purebred dogs has dropped by 11 percent in just a decade.

Dr. Becker then goes on to list specific breeds with reported median longevity that is lower in the 2014 survey compared with the 2004 survey.

As we have seen many, many times in the past, Dr. Becker cares far more for her own narrative than for the truth, and she is perfectly comfortable misrepresenting or ignoring facts if doing so will make a story that fits her beliefs and her pitch. This bit of fear-mongering is yet another example.

It is true that the life expectancy figures in the 2014 survey are lower for many breeds than those in the 2004 survey. So, does this mean our pets are not living as long as they used to? Not quite. For one thing, life expectancy figures for some breeds are actually higher in the 2014 report than in the 2004 survey. For example:

Breed 2004 Lifespan 2014 Lifespan
Flat-coated Retriever 9.83 years 10 years
Gordon Setter 11.08 years 12 years
Great Dane 6.5 years 7 years
Greyhound 9.08 years 10 years
Newfoundland 9.67 years 10 years
Old English Sheepdog 10.75 years 11 years

Cherry-picking just the figures that support your claims is a classic move in creating a story that fits what you want to say regardless of the facts.

Overall, the pattern of longevity in the two surveys is nearly identical, as you can see from these figures.

2004 Life Expectancy Histogram

uk-survey-2004-histogram

2014 Life Expectancy Histogram uk-survey-2014-histogram

As you can also see, however, the number of deaths reported is very different, and there is no statistical comparison to show whether the difference in the median or mean is significant. Why is this? Well, it turns out the data were collected in very different ways, they represent different methods and different dog populations, and the two surveys can’t legitimately be compared! Here’s what the actual authors of the survey have to say.

Please note there were substantial differences in the way the 2014 survey was conducted compared to the Purebred Dog Health survey, which was carried out in 2004…Given the difference in methodologies between the surveys, the data from each is not fully comparable and differences observed do not definitively imply changes in population parameters.

Furthermore, there were 5,864 deaths reported in the 2014 survey compared to 15,881 deaths reported in the 2004 survey. This significant drop reduces the likelihood of the sample accurately representing the wider dog population, and so would likely have an impact on median longevity figures if the two sets of data were compared, which would not be reliable.

In other words, Dr. Becker is comparing apples to oranges to show that apples were better in 2004 than in 2014. The actual reality, as determined by facts and evidence not one’s pre-existing beliefs, is that we don’t know whether our pets are living longer or not over the last 10, 20, or 30 years. There is excellent data in humans, and that shows conclusively that life expectancy and nearly every other objective measure of well-being has improved steadily for at least the last 100 years. For humans, at least, science and science-based nutrition, sanitation, and healthcare work far better than anything that went before.

There is no reason to believe the same is not true for our pets, however, there is also no reliable evidence either way. What we need is data, and a respect for legitimate scientific research, not more fear-mongering and twisting of the facts to sell an ideology.

Posted in General | 7 Comments

Acupuncture for Hip Dysplasia In Dogs: Putting some Spin on the Data

Another study of acupuncture in dogs has been published, and it’s worth a look. It’s a classic illustration of clearly negative results being misrepresented as positive. The authors set up a nice study of acupuncture compared with a common non-steroidal anti-inflammatory or an oral placebo for treatment of pain and lameness in dogs with hip dysplasia. The results pretty clearly showed no effect, and the authors duly wrote a conclusion suggesting acupuncture was a good choice for treating these dogs. Ah, the magic power of confirmation bias!

Teixeira LR, Luna SPL, Matsubara LM, et al. Owner assessment of chronic pain intensity and results of gait analysis of dogs with hip dysplasia treated with acupuncture. Journal of the American Veterinary Medical Association. November 1, 2016, Vol. 249, No. 9, Pages 1031-1039.

The authors of this study concluded that “acupuncture alleviated HD-related pain [and] …decreased lameness” and that “acupuncture performed with the protocol and acupoints used in this study appears to be a viable option for improving quality of life in dogs with HD.” Unfortunately, the results of the study do not support this conclusion.

For one thing, the authors stated that “the acupoints were selected on the basis of their functional effects in traditional Eastern medicine.” That is the only reference they make to the fact that the entire theoretical basis for the treatment rests on the mystical folk system of so-called Traditional Chinese Medicine (TCVM). This is undoubtedly intentional since it would be difficult to present acupuncture as a scientifically legitimate treatment if vets understood that needles were being placed in non-existent channels intended to control the flow of spiritual energy, balance heat and wind, and in keeping with other such pre-scientific notions. TCVM is incompatible with the scientific understanding of health and disease, and whether or not needling has any clinical benefits, it is irrational to use TCVM to select needling locations.

A more concrete problem with the study, however, is the data. The graphs below show the changes in various measures of pain and function over the course of the study, from 2 weeks before treatment to 6 weeks after. Treatment consisted of weekly acupuncture from Week 0 to Week 4 or an oral medication (carprofen) or placebo (lactose) daily from Week 0 to Week 4. Before even looking at the specific outcome measures, it is clear that all of the groups improved almost exactly the same and that overall the placebo group did as well or better than the acupuncture group. Not much more should be needed to conclude this study does not support acupuncture for dogs with hip dysplasia.

teixiera-2016-fig-1

Figure 1—Mean scores derived by use of the HCPI questionnaire completed by owners of HD-affected dogs 2 weeks before (week –2), immediately before (week 0), and at 2, 4, and 6 weeks after initiation of treatment with acupuncture (diamonds), carprofen (squares), or placebo (triangles) and by owners of HD-free dogs (cross) at week 0 only. Fifty-four HD-affected dogs were initially allocated to receive once-weekly sessions of acupuncture (5 sessions within a 30-day period), 4.4 mg of carprofen/kg orally once daily (2.0 mg of carprofen/lb; positive control group), or placebo capsules containing lactose (1 mg/kg [0.45 mg/lb]) orally once daily (negative control group). Acupuncture-treated dogs also received capsules containing lactose orally once daily and carprofen- and placebo-treated dogs were brought to the acupuncture clinic once each week for a total of 5 occasions within a period of 30 days. All of the oral treatments were administered for 30 days. Data from only 15 acupuncture-treated dogs, 16 carprofen-treated dogs, and 16 placebo-treated dogs were available for analysis. The HD-free dogs (n = 16), were selected from kennels or belonged to clients interested in HD-free certification for their dog. At each time point, each owner evaluation involved 3 assessment instruments: the HCPI; the CBPI, including total scores and those corresponding to pain severity and pain interference; and VASs regarding pain and locomotion. *At this time point, the value for each group of HD-affected dogs differed significantly (P < 0.001) from the value for the HD-free dogs.

teixiera-2016-fig-2

Figure 2—Median scores for pain severity (A), pain interference (B), and total pain scores (C) derived by use of the CBPI questionnaire completed by owners of the HD-affected and HD-free dogs in Figure 1. For the HD-affected dogs, assessments were made 2 weeks before (week –2), immediately before (week 0), and at 2, 4, and 6 weeks after initiation of treatment with acupuncture (diamonds), carprofen (squares), or placebo (triangles). The HD-free dogs (cross) were assessed only once (week 0). †At this time point, the value for the acupuncture-treated dogs differed significantly from the week –2 or week 0 value or both values. See Figure 1 for remainder of key.

teixiera-2016-fig-3

Figure 3—Median scores derived by use of a VAS for pain completed by owners of the HD-affected and HD-free dogs in Figure 1. For the HD-affected dogs, assessments were made 2 weeks before (week –2), immediately before (week 0), and at 2, 4, and 6 weeks after initiation of treatment with acupuncture (diamonds), carprofen (squares), or placebo (triangles). The HD-free dogs (cross) were assessed only once (week 0). See Figure 1 and 2 for remainder of key.

The study employed three subjective measures (pain scales designated HCPI, CBPI, and VAS scales) and one objective measure (force plate analysis). There were also several subsidiary categories within most of these measures. These were compared within and across treatments at multiple points in time before, during, and after treatment, yielding a large number of potential outcomes and comparisons. The more opportunities researchers have to select some comparisons and ignore others, the more opportunity for bias to determine the conclusions. The strongest studies are those in which the outcomes are consistent and all show the same result. That was certainly not the case for this study.

According to the authors, “Outcomes of the 3 treatments did not differ significantly [and]…kinetic evaluation did not differ among the groups.” All groups showed variation and overall improvement, but those treated with acupuncture did no better than the other groups, including the placebo. A few comparisons showed a difference between acupuncture and placebo or carprofen treatment in selected comparisons between a few points in time, but these were the exceptions, and the majority of potential outcome measures failed to show any difference. Basically, the authors cherry picked a few comparisons they could make statistically significant and largely ignore the vast majority that were not. This is cheating, though it is sadly very, very common, and not just in alternative medicine research.

The authors used carprofen as a “positive control” and oral lactose capsules as a placebo in this study. Though it might be helpful to include a sham acupuncture treatment as well, these are reasonable choices for control groups, and blinding appeared appropriate. There is robust evidence carprofen and other NSAIDs are effective analgesics in dogs with osteoarthritis.1-2 It is surprising, then, that carprofen had no apparent effect beyond placebo in this study. This calls into question the accuracy of the outcome measures employed. If a proven arthritis therapy didn’t appear to work better than placebo, it is unclear why we should trust the other results of the study.

Given the apparent lack of efficacy of the positive control and the failure to identify differences between treatment groups in nearly all outcome measures, it seems the most appropriate conclusion is that this study does not provide evidence to support the use of acupuncture for dogs with hip dysplasia. The data are far more compatible with the hypothesis of no difference between treatment and placebo, and the improvement seen in all groups is likely the result of nonspecific clinical trial effects (e.g. the Hawthorne effect3) and natural variation over time.

Negative findings are just as important and useful as data that do show efficacy. This study makes a valuable contribution to our understanding of the potential role of acupuncture in treatment of hip dysplasia. But it is misleading to characterize the results as supportive of utilizing this acupuncture protocol to treat pain of lameness associated with this disorder. Undoubtedly, people will cite this as a positive study when advocating acupuncture for dogs, but it takes very little investigation to realize it suggests exactly the opposite.

 

Update 12/27/2016:

I wrote a letter to the editor of the Journal of the American Veterinary Medical Association (JAVMA) which presented a shorter version of my critique of this article. The authors’ response was disappointing, to say the least, and a classic example of cognitive dissonance, the inability to objectively consider evidence that challenges a strongly held belief.

Dr. McKenzie is correct that in our study1 of dogs with hip dysplasia treated with acupuncture, carprofen, or a placebo, results for our subjective (Helsinki Chronic Pain Index, Canine Brief Pain Inventory, and visual analogue scales for pain and degree of lameness) and objective (kinetic variables obtained with a pressure platform) outcome measures did not differ among groups at any time point. In addition, results of kinetic evaluations did not differ over time in any of the groups.

Nevertheless, we did detect some differences among groups. For instance, the percentage of dogs with at least a 30% improvement in CBPI score, compared with baseline score, was significantly (P = 0.034) higher for dogs treated with acupuncture (13/15) than for dogs treated with a placebo (7/16), although not significantly (P = 0.446) different from the percentage for dogs treated with carprofen (11/16). Only 2 dogs required rescue analgesia, and both were in the carprofen group. In addition, only dogs in the acupuncture treatment group were found to have significant improvements in CBPI scores (total score and pain severity and pain interference subscores) and the VAS score for pain at various times, compared with baseline scores, and only dogs in the acupuncture and carprofen groups had improvements in the VAS score for locomotion. Therefore, we do not agree that the statistical testing created “an impression of effect,” as suggested by Dr. McKenzie.

We are aware that carprofen and other NSAIDs have been reported to be effective analgesics in dogs with osteoarthritis, and we do not have an explanation for why dogs in the carprofen group in our study did not perform better than dogs in the placebo group. However, in one of the reviews supporting the efficacy of NSAIDs in the treatment of osteoarthritis mentioned by Dr McKenzie, Innes et al2 reported that none of the selected studies met all 3 of their criteria for inclusion of essential elements for evidence-based medicine. Therefore, the efficacy of NSAIDs should perhaps be questioned and we should possibly seek new strategies to treat osteoarthritis.

The authors have considerable experience in working with acupuncture and conventional medical approaches to treat dogs with chronic neurologic and musculoskeletal diseases, and our clinical impressions support the benefit of acupuncture. Therefore, we feel confident in our conclusion that acupuncture may be a viable option for improving the quality of life in dogs with hip dysplasia. However, we understand that conventional medicine, including NSAIDs, is very important as a multimodal approach to alleviate chronic pain and argue that we should use all possible therapeutic tools to treat our patients. [emphasis added]

The idea that the failure of the positive control (carprofen, an NSAID) might indicate that the most widely used  and thoroughly studied class of drugs for arthritis pain is actually ineffective rather than that there is a serious flaw in this study is far-fetched, to say the least. And the final paragraph of this response illustrates the deep problem at the core of so much veterinary research, and in my opinion especially CAVM research; the use of science not to discover the truth but to buttress and provide marketing support for one’s existing beliefs. The fact that academic veterinarians and scientific researchers would openly admit that they believe a treatment is effective based on personal experience no matter what their own research evidence shows is a very bad sign for the health and usefulness of veterinary clinical research.

Reference

  1. Innes JF, Clayton J, Lascelles BD. Review of the safety and efficacy of long-term NSAID use in the treatment of canine osteoarthritis. Vet Rec. 2010 Feb 20;166(8):226-30.
  2. Aragon CL, Hofmeister EH, Budsberg SC. Systematic review of clinical trials of treatments for osteoarthritis in dogs. J Am Vet Med Assoc. 2007 Feb 15;230(4):514-21.
  3. McCambridge J, Witton J, Elbourne DR. Systematic review of the Hawthorne effect: New concepts are needed to study research participation effects. J Clin Epidemiol 2014 Mar; 67(3): 267–277.
Posted in Acupuncture | 3 Comments

The “Natural” Nonsense that is Applied Zoopharmacognosy

Introduction
A few years ago, I wrote about an interesting phenomenon called zoopharmacognosy. The idea is that animals might select specific plants or other substances to eat that would have therapeutic effects. An example might be an herbivore with a heavy parasite load eating a plant it doesn’t normally use as food but which happens to reduce the number of those parasites. It’s a popular idea among proponents of herbal medicine and folks who think the word “natural” is a meaningful guide to effective medical treatment because it reinforces their existing beliefs. However, the reality is a lot more complicated than such people seem able to admit.

There is some evidence that animals in the wild sometimes select plants to eat that might have health benefits. The best evidence comes from insects and other species with short generation times that produce large numbers of young and have rather simple, predominantly genetically determined behavior. Evolution can quickly select for changes in behavior that have a selective advantage in such species because small changes can readily spread if they give even a little advantage to a few individuals, and behavior is not very flexible or complex and so can be altered by small genetic changes.

There is much less reason to think zoopharmacognosy is a common or effective behavior found in more complex species, such as mammals. Most of the claims for this are simply uncontrolled observations with lots of assumptions and bias built in. And proponents of this idea generally ignore the fact that the availability of potentially medicinal plants is unpredictable, their composition and effects vary from plant to plant, region to region, and year to year, that we don’t have actual evidence for the real value of most plants considered “medicinal” by various folk medicine traditions, and finally that wild animals poison themselves or ingest non-food objects with deleterious consequences, which argues against a strong and reliable intuition about what is healthful.

Nevertheless, it should come as no surprise that not only do some alternative medicine proponents claim that zoopharmacognosy is an established and widespread phenomenon, rather than an interesting and largely unproven idea, they also use it to validate other ideas that are just as unproven and often even less plausible. Sadly, some even manage to profit from selling the idea, and a host of bogus remedies based on it, to pet owners. One such person is Caroline Ingraham, the proprietor of the grandly named Ingraham Academy of Applied Zoopharmacognosy.

Applied Zoopharmacognosy?
Somehow, Ms. Ingraham has created an apparently successful business selling the idea that your pet somehow knows which “natural medicine” they need for any illness and that she can teach you how to figure out which remedy your pet wants you to give him or her. According to her mission statement:

The Ingraham Academy of Zoopharmacognosy, headed by the founder of Applied Zoopharmacognosy Caroline Ingraham, promotes self-medication as a necessary component of domestic animal health and trains individuals in how to enable and recognize self-medicative behaviour in animals.

Since  it is not at all clear that zoopharmacognosy is a real or significant phenomenon among wild or domestic animals, claiming to teach people how to take advantage of it as a “necessary” part of their animals’ care is quite a stretch.

Who is Caroline Ingraham?
Ms. Ingraham does not provide a great deal of information about her background on her web site. While I think her claims should stand (or more likely fall) on the basis of the evidence rather than her credentials, I think it fair to ask whether she has any formal scientific training experience that might explain how she came to develop this questionable approach to veterinary medicine.  Unfortunately, all that is available on her web site is this:

Caroline Ingraham founded Applied Zoopharmacognosy and is the leading expert in this field of animal self-medication…. Caroline has featured in many scientific journals and articles, and has written numerous books on the subject.

At 22 years of age, Caroline studied the clinical use of essential oils for humans with one of the world’s leading experts in aromatherapy, Robert Tisserand and during her studies began to develop her approach towards helping animals using essential oils and other plant and mineral remedies. She later went on to study the French approach to the scientific use of essential oils with EORC (France) and Biologist Thomas Ingraham.

Her work encompasses an understanding of pharmacokinetics and pharmacology combined with animal self-medication.

Given that “aromatherapy” is a dubious practice and there is little evidence for any benefits that are not psychological in nature, studying with “experts” in this field is not a credential that carries much weight. And while she has written a number of books about aromatherapy and her invented field of “applied zoopharmacognosy,”  I have not yet found any reputable scientific publications from her on these subjects, despite the claim of being “featured in many scientific journals.”

 “Medicinal” Plants?
In addition to classes and books Ms. Ingraham happens to sell the remedies she suggests you let you pet choose among. These include essential oils and a range of plant-based products in various forms. Which raises the first of many problems with Ms. Ingraham’s claims: What are the “medicines” are we supposed to offer our pets?

There is no evidence for any meaningful medicinal value to the vast majority of the products that she sells. There is weak evidence for beneficial effects on subjective mood states, such as anxiety, in humans, but the notion that they can influence the outcome of serious diseases is entirely unproven and highly implausible. (1, 2, 3, 4).

And as I have discussed extensively before, herbal medicine is a complex subject, but the bottom line is there is no herbal product proven to have meaningful benefits for serious disease in companion animals. Most herbal products are untested and unreliable in terms of constituents. And there are serious risks to using untested and unregulated plant-based medicines. So whether or not your pet knows what they need to get better and can tell you, how is it helpful to offer them a selection of remedies that haven’t been shown to actually work?

Of course, the underlying reason for this is far more pragmatic. Not being a veterinarian, Ms. Ingraham cannot employ most medicines that have actually been proven to work. And even the “Founder of Applied Zoopharmacognosy” would likely admit that offering a selection of antibiotics, cancer drugs, pain relievers, and so on and letting your pet decide which drug it needed and how much to take would likely not result in a desirable outcome. That would demonstrate real trust in their inherent wisdom!

Undoubtedly, she would claim that this is different from what she recommends because pharmaceutical medicines are “chemicals” and are not “natural” so the inherent wisdom of animals to self-heal doesn’t operate with such remedies. That’s not a convincing argument, especially given that we at least we know the risks and benefits of real medicines, and feeding our pets her essential oils and ground-up leaves is just playing roulette with untested chemicals.

How Our Pets Communicate their Choices
The method by which Ms. Ingraham suggests our pets can indicate their choice of “remedy” is another problem with her approach. Even if our pets have a preference that is meaningful and appropriate (which has not been demonstrated), it is naïve to imagine that we can read our pets body language with a level of specificity that we can tell which remedy that want without introducing our own bias or influencing their behavior. Studies of drug detection dogs have shown that dogs are very sensitive to human expectations and will often misidentify substances they are supposed to search for when their handler has a pre-existing and incorrect belief about where drugs are located. And the caregiver placebo effect is a well-known phenomenon in which owners and veterinarians see what they hope or expect to see in their dogs rather that accurately observing their behavior.

So what cues does Ms. Ingraham suggest we look for in reading our dogs’ choices? Without buying her book or taking her class (and yes, I know her defenders will say I should do so before evaluating the method, so here is where you can find my prior explanations for why this is not a useful or legitimate argument), I was able to find some of her recommended cues on the site where she sells her products:

Positive reactions:

  • Sniffing
  • Smelling
  • Stillness
  • A vacant look
  • Blinking
  • Stretching
  • Closing the eyes
  • Lowering the head or lying down
  • The work is all about not rushing, and closely observing your dog.

Positive reactions mistaken for negative reactions:

  • Grimacing (helps open the vomeronasal organ)
  • Barking or lunging at the extract Anxious (behaviour usually signifies a release, followed by calm)
  • Jumping away quickly, or backing away from the aroma (usually indicates releasing an unpleasant memory)

Negative reaction:

Lack of interest, or distracted

This list has all the specificity of a horoscope or a homeopathic proving. A lack of interest is a negative sign, but a vacant look is a positive sign. Lunging at the remedy indicates selection, but so does backing away from the remedy. Even blinking is supposed to be a positive sign! Clearly, this is a perfect example of the use of vagueness to allow any interpretation the person making the claim desires to be supported. It is exactly the sort of self-deluding approach to animal behavior that lets pet psychics and their clients convince themselves that bit of magical nonsense is real.

What About Eating Socks?
Of course, any claim that our pets know what’s good for them and choose to eat the healthiest food or most appropriate medicinal plants has to consider the inevitable question of why, if they are so wise, do our animal companions try to kill themselves by eating socks, batteries, massive overdoses of medication, their own feces and vomit, and any number of other distinctly unhealthful substances?

Ms. Ingraham’s response to this question also strikes me as pretty unconvincing. Basically, she claims that our animals may be too hungry to resist toxic plants, that they are fooled by “artificial” chemicals or other substances, such as sugar and flavorings, into thinking unhealthy substances are good for them, or that in nature they would eat a natural “antidote” to a toxic plant after eating that pant but that they don’t always have access to such anecdotes in captivity. None of this reasoning makes much sense, and it ignores both the self-destructive ingestive behavior seen in wild animals as well as the impact of domestication on the physiology, diet, and behavior of many animals, such as dogs and livestock.

What’s the Harm?
There are a number of ways in which the idea of “applied zoopharmacognosy” can be harmful to our pets. For one, the remedies Ms. Ingraham recommends are largely untested, and this means not only that they might not be helpful but that we can’t assume they are safe. As I’ve pointed out many times, plant-based chemicals can do plenty of direct harm.

Perhaps the greater risk is the indirect harm caused by relying on nonsense instead of seeking legitimate medical treatment. This is exacerbated by suggesting that this method at be more reliable than conventional medicine, as the ever-unreliable alternative medicine advocate Dr. Karen Becker has done.

becker

To suggest doctors often choose the wrong remedy whereas pets intuitively do a better job when selecting from untested and unregulated alternative products is irresponsible and misleading. And Dr. Becker seems to be forgetting that “wild animals” live shorter lives far richer in parasitism, disease, and suffering than our pets, despite their freedom from misguided doctors and access to “Nature’s pharmacy.”

The following testimonial is a particularly chilling example of how dangerous this sort of delusion can be. A student of Ms. Ingraham describes her use of the nonsense she was taught to treat what she had good reason to believe was a potentially life-threatening illness.

capture-edit

The fact that the owner got away with this response to what might have been a deadly illness does not justify it. The fact that Ms. Ingraham has chosen to post this testimonial on her Facebook page as part of the process of advertising her services suggests she may recommend or approve of using her method and her products in place of proper veterinary care, even in potentially life-threatening situations. That is certainly the impression her student acquired in her class. If this is true, it is a dangerous and irresponsible practice.

Bottom Line
There is little evidence that selection of medicinal plants or other substances by animals in their natural habitat or by domesticated animals is a common behavior with substantial health benefits. Zoopharmacognosy is an interesting phenomenon, but there is very limited evidence for it in most species. Wild animals are generally less healthy and shorter-lived than domesticated animals provided conventional healthcare, nutrition, sanitation, and other basic husbandry, so the concept Ms. Ingraham is selling is mostly a variety of the appeal to nature fallacy.

There is also virtually no evidence that the use of essential oils or many of the plant extracts Ms. Ingraham sells is safe or effective for any serious health condition. Aromatherapy has not been shown even in humans to have significant health benefits, though there may be some mild psychological effects, and in veterinary species there is no reason to think essential oils can dramatically improve health. Likewise, while herbal medicine is a bit more plausible and promising in some ways, it has largely failed to prove its worth in controlled scientific research, and most of the herbal and other plant remedies Ms. Ingraham sells and recommends have not been proven to have value or even to be reliably safe.

The process of letting our pets “select” a remedy is subjective and deeply vulnerable to bias and caregiver placebo effects.

Most importantly, Applied Zoopharmacognosy is yet another unproven and implausible practice that places pets in danger when it is used as a substitute for real veterinary care. Even if the remedies themselves are harmless, which is not certain, the example above illustrates how it can be very dangerous if people are led to believe that these methods and products can replace appropriate medical care.

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Why Anecdotes & Testimonials Can’t Be Trusted

By far the most frequent response I get to any article critical of claims for an alternative therapy or focused  on the lack of good evidence for such claims is an appeal to anecdotal evidence.  Some variation on “I tried it and it worked for me” or “Don’t knock it ’til you’ve tried it” is a common and, for many people,  persuasive rebuttal to even the most carefully researched and objective, science-based critique. Since I end up responding to such anecdote-based rebuttals almost every day, I have written frequently about why anecdotes and testimonials aren’t reliable evidence and why personal experience isn’t a necessary, or even very good, way to evaluate a medical treatment. I am collecting these articles here for convenience, both as a reference for interested and open-minded readers and so I only have to post one link when I answer such arguments.

Why We’re Often Wrong
Testimonials Lie
The Role of Anecdotes in Science-Based Medicine
Don’t Believe your Eyes (or Your Brain)
Caregiver Placebo Effects

Though a bit more technical and aimed at vets, this article also touches on cognitive biases which reduce the reliability of uncontrolled personal observations.

McKenzie, B. Veterinary clinical decision-making: cognitive biases, external constraints, and strategies for improvement. Journal of the American Veterinary Medical Association. 2014;244(3):271-276.

Posted in Topic-Based Summaries | 3 Comments

Evidence Update- Stem Cell Therapies for Companion Animals

Introduction
One of the most frequent recurring topics on this blog has been stem cell therapies. Generally, I have concluded that various types of stem cell therapies are plausible and promising, but they are unfortunately being marketed with claims and uses that go far beyond any reasonable scientific evidence. Since the last time I reviewed the subject, a couple of interesting articles have been published, so I thought it was time for an update.

Research Review
The first is a narrative review of companion animal stem cell studies published earlier this year.

Andrew M. Hoffman, Steven W. Dow. Concise Review: Stem Cell Trials Using Companion Animal Disease Models .STEM CELLS 2016;34:1709–1729

As a narrative review, this paper does not have the rigor, controls for bias, or focus of a systematic review. However, it provides a nice informal summary of the problems for which stem cell therapies have been investigated in companion animals, the different types of therapies evaluated, and the strengths and weakness of the literature. The paper reviewed companion animal stem cell studies from 2008 through 2015.

The key findings are that there are not many studies, the studies that exist are very inconsistent in terms of the specific treatment they tested, and almost all of the studies have significant limitations.

Arthritis is the most common problem for which stem cell therapies have been investigate in companion animals. However, the specific therapies used are always somewhat different, so there is no replication or consistency in the literature. Studies use different doses, preparation methods, methods of administration, sources of stem cells, and measures of effect. This hodgepodge of methods indicates the very early stage of research in this area, and we cannot yet draw reliable conclusions about the value or safety of particular products for specific uses. And most studies included only a handful of patients, which significantly weakens any conclusions based on them.

In addition, the majority of the studies did not employ the basic mechanisms of controlling for bias and error, including randomization of subjects, blinding of clients and investigators, and placebo controls. Subjective measures of effect were also most commonly used, which make the lack of such bias control methods particularly significant. While most studies claimed to find some beneficial effects, these claims have to be taken with a grain of salt due to these methodological issues.

The same general issues pertained to the other clinical problems for which stem cells have been studied. Intervertebral disk disease, inflammatory bowel disease, dry eye, kidney disease, and a few other conditions have been the subject of stem cell studies. These again involved very few patients, a variety of quite different treatments, and few if any controls for bias, confounding, and other important kinds of error. The results were inconsistent, some showing apparent benefits and others not, and a few showed evidence of some short-term side-effects. Overall, no general conclusion about the clinical value of stem cell therapies for any of these conditions can be justified by the existing research.

The authors conducted the review primary to make the case that companion animals might make a good research field for studying stem cell therapies with a long-term goal of applying them to humans. However, even with an optimistic slant, the authors’ conclusions were quite cautious:

In conclusion, companion animals with naturally occurring diseases analogous to human conditions can be recruited into clinical trials and provide realistic insight into feasibility, safety, and biologic activity of novel stem cell therapies.

However, improvements in the rigor of manufacturing, study design, and regulatory compliance will be needed to better utilize these models… Based on review of the literature, the utility of companion animals in stem cell trials is in the very early stages.

They also provided some recommendations for ways to improve the companion animal literature on stem cells, which would benefit both those with the ultimate goal of treating humans and those of us interested in finding safe and effective treatments for veterinary patients.

To facilitate expanded development and application of companion animal disease model research in the future, the following areas need to be addressed with additional education, communication, and industry and government support:

Increased collaborations between physicians and veterinarians to address specific disease conditions and models, consistent with the One Health paradigm.

Increased understanding of the molecular pathology of specific diseases in companion animals, and detailed comparison to human samples and analogous disease processes.

Greater characterization of companion animal stem cells and their cellular products.

The use of more rigorous double blind (owner, investigator) randomized clinical trial designs whenever possible. Education of the public about the value placebo-controlled studies.

Greater clinical trial infrastructure (personnel, equipment, specialized instrumentation, and imaging) to support efficient recruitment into clinical trials.

Central registry of veterinary clinical trials (currently in progress at the American Veterinary Medical Association).

Biorepositories and registries of companion animal disease tissue, biofluids, and nucleic acids or other samples.

Improved availability of companion animal specific reagents, in particular probes for protein detection and quantification.

The application of FDA guidance (NADA, INAD, pre-IND) in clinical trials involving stem cell treatments in companion animals (client owned animals).

I have highlighted a few of the recommendations of particular importance for making such research useful to veterinary patients. The establishment of a clinical trial registry, improved rigor and quality of research, and the application of FDA-level standards would all greatly improve the quality of stem cell research in veterinary medicine and improve the chances of finding truly useful therapies. This last measure is particularly relevant to the other study I wanted to discuss.

Allogenic Stem Cells for Arthritis

Harman R, Carlson K, Gaynor J, et al. A Prospective, Randomized, Masked, and Placebo-Controlled Efficacy Study of Intraarticular Allogeneic Adipose Stem Cells for the Treatment of Osteoarthritis in Dogs. Frontiers in Veterinary Science. 2016;3:81.

This is by far the best quality stem cell research study I have yet seen, and the reason is likely that the study is part of an effort to get FDA approval for a specific stem cell treatment. While the study has limitations, as all research does, it is well-designed and conducted and provides pretty robust results.

The major limitations are that the study was industry funded, which has been associated with some risk of bias in human pharmaceutical research, and the outcome measures were quite subjective. However, the mechanisms for controlling potential bias were quite thorough, including appropriate randomization, blinding, pre-specific outcome measures, and a lack of the statistical hocus pocus that is so common in veterinary clinical trials. Overall, the study provides very good evidence for a potentially clinically meaningful effect.

Interestingly, the study investigated a allogenic stem cell product, meaning one derived for a dog other than the intended patient. Most current stem cell products used in companion animals involve taking fat or blood form a patient, processing it in various ways, and then using that product in the same patient (called autologous stem cell therapy). While this has some advantages in terms of minimizing the risk of infections and adverse reactions to foreign material, it requires these patients to undergo anesthesia and surgery to collect the sample, which has its own risks and costs, and it yields inconsistent material for treatment. An off-the-shelf stem cell product derived from a single patient and then processed and maintained by the manufacturer can be better standardized and assessed for quality, it can be a more predictable therapy, and it can avoid additional anesthetic and surgical procedures for patients, so there are some advantages to this approach.

The study randomized 93 dogs with arthritis in one or more joints to treatment with the stem cell product or a placebo injected into the affected joints. 74 of the subjects were included in the final analysis, with the rest being excluded for failing to adhere to the study procedures or other reasons. The primary outcome was the owner assessment 60 days after treatment of three specific activities chosen by the owner at the beginning as important measures of comfort and function. The secondary outcomes were assessments by the veterinarians treating the patient and overall assessments by both owner and vet. These are inherently subjective outcome measures, which are somewhat less reliable than more objective measures, such as force-plate analysis. However, the mechanisms for minimizing bias were good enough to make these reasonable choices despite the potential for caregiver placebo effects.

The primary outcome showed both a statistically significant and a clinically meaningful difference of about 24% in degree of improvement between placebo and treatment groups. In other words, the placebo group owners reported a 55% improvement, which shows how strong a placebo effect by proxy can occur. However, the treatment group owners showed a 79% improvement, which is enough of a difference to suggest some real change.

The veterinarian assessments also showed large and significantly greater improvements in the treatment group compared to the placebo group. The overall owner assessment was the only measure to show a difference too small to be statistically significant. However, the size of the effect and the consistency of the effect across different measures are arguably more important.

So overall, the study strongly suggests this particular stem cell treatment had some real beneficial effects, and no significant undesirable effects were noted, though with stem cells many of the problems they might cause would not necessarily be expected to appear only 60 days after treatment. This does not, of course, validate all of the myriad of stem cell therapies and uses of these out there. In particular, it doesn’t necessarily tell us that the autologous stem cell products which are most widely used have similar benefits.

Naturally, no single study is ever sufficient alone to prove safety and efficacy. The FDA approval will likely involve further research which hopefully will support these findings. If so, this would be an important step towards producing a reliable and consistently effective stem cell treatment for arthritis in dogs. I have always been cautiously hopeful about this approach, and I am pleased to see the very beginnings of the kind of research evidence needed to make stem cell treatments a reasonably evidence-based procedure.

Bottom Line
Overall, the evidence supporting stem cell therapies in companion animals is very weak and preliminary. More research is absolutely appropriate, but clinical use is still an uncontrolled experiment on our patients and should only be done with clear and detailed discussion with owners about the uncertain risks and benefits and after all treatments with better supporting evidence have been considered.

The best evidence so far, a clinical trial involving treatment of dogs with arthritis, does suggest that allogenic stem cells injected into arthritic joints may improve comfort and function enough to be worthwhile, with no apparent short-term side-effects. Even for this process, however, more research is needed to justify widespread use. Hopefully, this will emerge in the course of pursuing FDA approval for this method.

 

Posted in Science-Based Veterinary Medicine | 2 Comments

Overdiagnosis

Overdiagnosis is now recognized as a common and serious problem in human medicine that causes substantial harm in terms of unnecessary costs, wasted resources, and patient and caregiving suffering. International conferences (e.g. Preventing Overdiagnosis) and special features in major medical journals (e.g. Too Much Medicine in the British Medical Journal and Less is More in the AMA journal) have been dedicated to discussions of overdiagnosis and overtreatment. In 2012, a consortium of 70 specialty groups created the online resource Choosing Wisely to help physicians and patients make evidence-based decisions that reduce overdiagnosis and overtreatment. Even an influential popular book has been written on the subject: Overdiagnosed: Making people sick in the pursuit of health.

Changes in clinical practice guidelines and public education strategies have resulted from the growing recognition of the risk of overdiagnosis in human medicine, including highly publicized changes in recommendations for prostate cancer screening in men and breast cancer screening in women.

However, there seems to be little discussion in the veterinary literature or veterinary curriculum of the problem of overdiagnosis and the risks it poses to veterinary patients. In the past, IK have discussed the evidence regarding potential sources of overdiagnosis in veterinary medicine, such as pre-anesthetic blood testing (also c.f. 1, 2). However, among veterinarians and animal owners, there seems to be a near total lack of awareness of the fact that sometimes testing for and diagnosing a condition can actually lead to a worse outcome for the patient than not diagnosing it.

This is a counterintuitive idea, but it is well-established in human medicine.  Changes in guidelines for prostate cancer screening, breast cancer screening, thyroid cancer testing, and many other conditions have come about because of the recognition that inappropriately targeted diagnostic tests can harm patients and waste resources on treatments that do not make people better. It is time we took a serious look at this issue in veterinary medicine, and made an effort to collect the data needed to understand its scope and causes so that we can better serve our patients. Since I was unable to find virtually any discussion of the subject in the veterinary literature, I have written a commentary raising the subject, which I hope will stimulate needed discussions on this topic.

McKenzie, BA. Overdiagnosis. Journal of the American Veterinary Medical Association. 2016:249(8);884-889.

 

Posted in General, Science-Based Veterinary Medicine | 2 Comments

Evidence Update- Yunnan Baiyao: Still No Persuasive Evidence of any Benefits

Back in 2010, in the early days of this blog, I reviewed the evidence for the Chinese herbal supplement Yunnan Baiyao. At the time, I found only very low-quality evidence concerning the potential risks and benefits of this product.  Some in vitro studies suggested possible mechanisms by which the product might help limit bleeding. However, clinical trials were sparse, low quality, and often at high risk of bias. Many studies have been conducted in China, and these must be viewed very skeptically given that past reviews have found extreme publication bias for alternative medicine studies in China (one review found absolutely no negative studies were published there), and a recent investigation by the Chinese government found up to 80% of drug trials published there were fraudulent or otherwise unreliable. Also deeply concerning was the fact that the company producing the product refuses to disclose its exact ingredients.

So the bottom line in 2010 was that Yunnan Baiyao is an unregulated and largely untested secret recipe, and it is unclear how it can have its purported effect, stopping bleeding, without having any potential risks, including most obviously excessive blot clotting, which is the cause of strokes and other serious medical problems. So what new information is there since 2010?

There have been a few additional studies published, but they tend to fit the profile of those already available five years ago: mostly from China and mostly not clinical trials with robust design and execution. A couple of new studies have been published directly related to veterinary use.

 

Shmalberg J, Hill RC, Scott KC. Nutrient and metal analyses of Chinese herbal products marketed for veterinary use. J Anim Physiol Anim Nutr (Berl). 2013 Apr;97(2):305-14

This study evaluated the nutrient and metal content of a number of Chinese herbal products, including Yunnan Baiyao. The Yunnan Baiyao did contain potentially toxic heavy metals,  such as lead, though the single batch tested suggested the levels were probably not high enough to cause illness, at least at typical doses over a limited period of time.

 

Wirth KA, Kow K, Salute ME, Bacon NJ, Milner RJ. In vitro effects of Yunnan Baiyao on canine hemangiosarcoma cell lines. Vet Comp Oncol. 2016 Sep;14(3):281-94.

This study found that Yunnan Baiyao could kill cells of the canine cancer hemangiosarcoma in vitro. This kind of study is a necessary precursor to clinical testing of drugs, but it is important to point out that it says nothing about whether the substance tested would be useful in actual patients. Bleach, for example, kills cancer cells in vitro, but that doesn’t make it a useful cancer drug.

 

Murphy LA, Panek CM, Bianco D, Nakamura RK. Use of Yunnan Baiyao and epsilon aminocaproic acid in dogs with right atrial masses and pericardial effusion. J Vet Emerg Crit Care (San Antonio). 2016 Sep 26. doi: 10.1111/vec.12529. [Epub ahead of print]

This study actually evaluated a common clinical use for Yunnan Baiyao. Dogs with tumors on the right atrium of the heart and fluid in the pericardium, the sac around the heart, almost always have a type of cancer known as hemangiosarcoma. This cancer typically lodges in places like the spleen, liver, or heart, and it usually causes severe bleeding. The conventional therapies available aren’t very effective, and most dogs with this disease die or are euthanized within a few days to a few months. As always, there are exceptions who survive much longer, but generally the outlook for this disease is poor, especially for the form that occurs in the heart.

The lack of highly effective conventional treatment makes this disease a popular target for alternative therapies, and Yunnan Baiyao has come to be used fairly frequently. Though the evidence has not been available to substantiate any benefits, there is a “what is there to lose?” attitude in these cases, so even many conventional vets are willing to give it a try. Though there are, as always, plenty of miraculous anecdotes out there (and, of course, not many negative ones since who goes out of their way to tell everyone about something they tried that didn’t work?), this study is the first formal research in regular clinical patients.

The study was retrospective, meaning that the authors simply looked through records of animals that had been treated for a right atrial mass and fluid around the heart. Some were treated with only conventional supportive care, and some got Yunnan Baiyao, either alone or with another potential anti-bleeding drug called aminocaproic acid. There was no randomization and no blinding, so it is possible that any results could be due to factors other than the drugs given. However, the authors checked for differences in many characteristics of the patients that might influence the results and didn’t find any.

So what were the results?

The median time to recurrence of clinical signs in the treated group (12 d, range 1–186 d) was not significantly different from the control group (14.5 d, range 1–277 d)…The median survival time of dogs in the treated group (18d, range 1–186 d) was not significantly improved compared to the control group (16 d, range 1–277 d; Table 1, Figure 1). The median survival of the 8 dogs that received YB and EAC (17 d, range 1–88 d) was also not significantly improved compared to the 16 dogs that received YB alone (31 d, range 1–186 d). There were no side effects attributed to the YB or EAC use in any dogs during the study period.

Basically, there were no differences in any of the symptoms or in the survival of dogs whether or not they got Yunnan Baiyao. There were no apparent side effects either, but that isn’t too surprising in a group of dogs that only lives 2-4 weeks after being treated.

While this study, like all research has limitations, it is the best evidence concerning real-world clinical use of Yunnan Baiyao in dogs so far, and it found no effect at all. This is not the final word on the subject, of course,  since there are other conditions, other circumstances, other doses, and all sorts of other ways in which the product could be tested. However, as of now the evidence does not support any benefits. And the fact that, as the authors point out,  “its

exact compositional formula is a closely guarded secret by the manufactures and like many nutritional supplements, is not subjected to any quality control measures as compared to pharmaceuticals.” Most vets, and certainly most alternative medicine vets, would lose their minds if it was suggested we should use a drug company product not only without evidence of effectiveness but without even knowing what is in it! Yet, for some reason, a different standard is often applied to herbal remedies like Yunnan Baiyao, which places our patients at unnecessary risk.

Bottom Line

Despite some suggestive in vitro and low-quality studies, the best evidence available so far does not support that Yunnan Baiyao has any benefit for dogs. The fact that it is unregulated, that there is demonstrated inconsistency in the mineral and metal contents of Yunnan Baiyao from different sources, and that the ingredients are still kept secret by the manufacturers, should also give clinicians pause in considering this for their patients. While use in desperate circumstances when there are no established effective therapies may be reasonable, clients should clearly understand that this is at best a rolling of the dice and that the safety and effectiveness of this product for any use has not been established.

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IAABC Interview Discussing CAVM and EBVM

Here is an interview I did recently with an association of animal behavior consultants. We discussed a number of subjects that appear frequently here,  including the role of evidence and anecdote in evaluating treatments for animals, and the risks of alternative medicine.

iaabc

Posted in Presentations, Lectures, Publications & Interviews | 1 Comment

Scientists Warn that Donald Trump is the Most Anti-Science Candidate for President

Since my review of the presidential candidates’ positions on science issues earlier in the week, I have seen a number of efforts by other scientists to warn the scientific community and the public that Donald Trump stands out as the most egregiously and consistently anti-science candidate in this year’s election.

One effort is an open letter authored by a number of prominent scientists, including Harriett Hall and Steven Novella, two prominent skeptics and authors of the Science-Based Medicine Blog:

Scientists say: “Donald Trump is Not Who We Are”

As members of the scientific community, we invite our colleagues to stand together in making it clear that Donald Trump’s views on many pressing topics are at odds with scientific reality and represent a dangerous rejection of scientific thinking.

There should be no place for this kind of rhetoric – or this kind of attitude toward expertise itself – in the halls of government.

As a community, we affirm the values that make us who we are: curiosity, skepticism, integrity, and simple adherence to the facts.

Vaccines save lives every day, but Mr. Trump has stoked discredited fears about vaccines and autism and accused doctors of lying to people about them.

Every major country on Earth is adapting to a changing climate and reducing emissions from fossil fuels, but Mr. Trump has claimed it is a hoax, a statement that prompted a response from hundreds of members of the U.S. National Academy of Sciences, the country’s leading scientific advisory body.

Mr. Trump’s running mate, Mike Pence, has a similarly disconcerting record:

He also dismisses the evidence that climate change is caused by burning fossil fuels.

He delivered a speech to the House of Representatives challenging the teaching of evolutionary science in classrooms based on a misreading of how evolution works.

Nearly 40 years after the Surgeon General first warned us about the dangers of smoking, Pence claimed that “smoking doesn’t kill” and said there was no direct link between smoking and lung disease.

These are not the words and thoughts of responsible leaders.

The letter currently has 712 signatures, including mine.

Another open letter signed by 375 members of the National Academy of Sciences warns of the dangers of  denial of human-caused climate change and of a refusal to participate in international efforts to combat it, both positions embraced by Donald Trump and rejected by all of the other candidates:

An Open Letter Regarding Climate Change From Concerned Members of the U.S. National Academy of Sciences

Human-caused climate change is not a belief, a hoax, or a conspiracy. It is a physical reality.

During the Presidential primary campaign, claims were made that the Earth is not warming, or that warming is due to purely natural causes outside of human control. Such claims are inconsistent with reality.

The political system also has tipping points. Thus it is of great concern that the Republican nominee for President has advocated U.S. withdrawal from the Paris Accord. A “Parexit” would send a clear signal to the rest of the world: “The United States does not care about the global problem of human-caused climate change. You are on your own.” Such a decision would make it far more difficult to develop effective global strategies for mitigating and adapting to climate change.

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