Book Review- Lifespan by Dr. David Sinclair

As part of my efforts to learn as much as I can about both aging biology and also the effective communication of geroscience research, I have been reading popular books on the subject by influential figures in the field. While the details of the science are more accurately and thoroughly expounded in the scientific literature, the philosophy, history, and ethos of the aging biology field is often best explicated in books for the general public. And while I have been communicating to many different audiences about science for many years, this experience has centered on veterinary medicine, evidence-based medicine, and alternative medicine. Being relatively new to the aging biology field, I am enjoying learning the metaphors and techniques various authors use to communicate about the field to those who are not specialists in the subject.

As always, I endeavor to share what I learn through this blog, so I will be posting a series of reviews of the aging biology books I have read. I am starting today with Dr. David Sinclair’s book Lifespan: Why we age-and why we don’t have to.

Dr. David Sinclair is a bit of a controversial figure in the geroscience community. He is recognized as a talented and productive scientist. He is also an eloquent and persuasive advocate for aging biology research. Yet he is prone to hyperbole and enthusiasm that goes beyond what can be supported by reliable data. He is known for using, and at least tacitly or indirectly recommending, anti-aging interventions that have not yet been appropriately tested for safety and efficacy in humans. The ambivalence Dr. Sinclair inspires has been well-characterized by his friend, and fellow renowned aging biology researcher and author, Dr. Steven Austad:

“He’s a superb scientist, as well as a superb salesman. You talk to him about science and you won’t find many more knowledgeable, incisive experimentalists as David. And then you can listen to the stuff he says on TV and be like, What the hell is he talking about??

Dr. Sinclair’s book is an excellent example of both the good and the bad in the popularization of science. He makes extensive and effective use of personal stories and anecdotes, and he humanizes even the minor characters in his story, offering engaging personal tidbits or colorful characterizations of scientists whose work he references. The writing is clear and entertaining, and the analogies and similes he chooses to explain scientific concepts are usually quite effective. He summarizes complex biology succinctly and accurately. Nuance and uncertainty are sometimes smoothed over, but not usually to the point of misleading the reader.

Lifespan also does a thorough and respectable job of covering not just the science of longevity but some of the history of the field as even some of the philosophical and ethical implications of efforts to extend human lifespan. Much of the book goes beyond the science and research evidence, but that is often an important part of popular science literature—to put the evidence in context and explore the ideas and implications beyond the data. From the perspective of science communication, this is an enjoyable and effective book.

Unfortunately, Dr. Sinclair’s book also contains examples of many of the flaws and foibles of popular science. He makes free with exuberant speculation, promises to the reader, extrapolation and exaggeration. He emphasizes his own credentials in a way that invokes an argument from authority, at least indirectly implying his speculations and beliefs should hold more credibility than can be justified by actual evidence simply because of who he is. Similarly, while he is careful to employ qualifiers and caveats, his use of anecdote and personal experience often goes beyond illustration to at least suggest that these anecdotes are evidence supporting his beliefs and practices. 

Like many accomplished scientists, Dr. Sinclair undoubtedly believes his perspective on a complex topic is the “right” one in most respects. Popular science literature allows him a freedom to promote his views and agenda that the strictures of the scientific literature do not. The picture he creates of the field is clear and not grossly distorted, but it very much takes his perspective, and there are plenty of elements other experts in the field would take issue with. 

As far as specifics, the review of the aging field and some of the main theories of aging is clear and readable. Dr. Sinclair is reasonably fair in his summaries, though he does editorialize and pass judgement on many of the ideas he covers. The review is clearly intended to lead inexorably to his personal ideas about aging, which is fair enough for a popular science book. He also makes an eloquent defense of the position that aging should be conceived and treated as a disease, and that the alternative view of it as a natural feature of the life cycle impedes efforts to understand and combat it.

The book then reviews some of the longevity-promoting interventions that have been studied in animal models, such as caloric restriction and drugs like rapamycin and metformin. This section tends to emphasize the positive and gloss over the limitations and uncertainties of many of these interventions, and the general reader is likely to come away with an erroneous sense that we already have clearly effective anti-aging therapies that we should reasonably be using in humans. 

This is exacerbated by Dr. Sinclair’s descriptions of using various interventions himself and for his family members. While he makes appropriate caveats about anecdote and evidence, there is no question that he believes he and his relatives have benefitted from using treatments not adequately tested in humans. His enthusiasm and credentials are very likely to convince some readers that they should follow his example regardless of the lack of evidence. 

It is understandable that when someone believes they have found a powerful health-promoting practice that they would want to share it with others, but this sort of promotion of insufficiently tested practices is a hallmark of pseudoscience. It is problematic for a legitimate scientist to promote untested therapies using tactics associated with the promotion of pseudoscience, not only because it may lead people to adopt unproven and potentially unsafe practices but because it makes the demarcation problem worse and diminishes the standing of science and scientists as sources of reliable guidance.

The latter sections of the book lay out a very optimistic view of the potential for geroscience research to extend healthspan and lifespan. There is always a tension between hope for the potential of scientific research in a particular field and recognition that many hard problems are truly hard to solve, and that a surprising proportion of good ideas turn out to be wrong. Dr. Sinclair errs, if it can be characterized as an error, on the side of exuberance and optimism. This seems a natural feature of his temperament, and it certainly fits with the desire of any researcher to present their area of expertise as likely to be fruitful, even world-changing. 

A different balance between creative and critical thinking, skepticism and hopefulness, can be struck in this domain, as in any other area of rapidly growing and changing scientific knowledge. I would be inclined to be more cautious about my speculations than Dr. Sinclair chooses to be. The future, and the data, will be the final arbiter of how much optimism about the field as a whole, or specific hypotheses in it, was justified. It is easy to see, however, why some of Dr. Sinclair’s colleagues feel his enthusiasm sometimes goes too far.

I appreciated Dr. Sinclair’s discussion of the potential negative impact of pursuing increased longevity for humans. It is an issue everyone in the field should give serious thought to. Again, his answers are exceedingly optimistic and rely on a confidence in technology and human behavior to save us from the potential consequences of our discoveries that I find hard to support with the evidence of history. Still, a popular science book is most often an opportunity to make a case for one’s own perspective on a subject, and I cannot fault him for doing so even if I am not entirely convinced by the case he makes.

Overall, Lifespan is an enjoyable read and contains a lot of effective and accurate explication of key concepts and findings in longevity science. It often promotes a distinctive perspective that may well not be shared by other experts in the field, but not usually in a way that involves gross misrepresentation of the facts. Dr. Sinclair clearly prefers optimism to skepticism, and his portrayal of the state of geroscience is likely to lead many readers to see our ability to alter human health and lifespan as far more advanced than it actually is. 

Dr,. Sinclair is entitled to shape the narrative of geroscience in his book to fit his own optimism and enthusiasm. However, when he uses anecdotes and references to his credentials, rather than reliable, relevant scientific evidence, to influence readers to accept this view, I think he does edge into the territory of snake oil salesmen, at least in his methods. The line between genuine and fair optimism and misleading salesmanship is a narrow one, and Dr. Sinclair treads right along it, wobbling to either side throughout the book. I would still recommend reading Lifespan, but as always I would encourage a skeptical, critical reading balanced with other sources, some of which I will review in the future.

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