Ageing as a disease — and what we might do about it

David Sinclair is a geneticist at Harvard Medical School who has spent his career studying why organisms age, and whether anything can be done about it. Lifespan, published in 2019 and co-written with journalist Matthew LaPlante, advances a specific and controversial claim: that ageing is not simply the passage of time but a disease — a process driven by the loss of genetic information — and that it may be treatable.

Sinclair's framework, which he calls the Information Theory of Aging, proposes that cells age because the epigenetic information that tells each cell which genes to express becomes progressively corrupted. The genome is compared to a scratched disc: the underlying data is still there, but the reader can no longer interpret it cleanly. Restoring that information, Sinclair suggests, could reverse the functional decline we call ageing.

Central to his account are proteins called sirtuins and a molecule called NAD+, which sirtuins require to function. Sinclair argues that maintaining NAD+ levels — through caloric restriction, exercise and potentially certain supplements — may support sirtuin activity and slow epigenetic degradation. He is candid that he takes compounds including NMN, though he is explicit that this is personal experimentation, not clinical recommendation.

The book has attracted pointed scientific criticism. Other researchers in the ageing field have argued that Sinclair overstates the evidence for sirtuins — some studies suggest sirtuins do not extend lifespan in certain model organisms — and that the leap from laboratory findings to human interventions is larger than the book implies. Read as a tour of one scientist's ambitious hypothesis, accompanied by a clear-eyed account of its limits, Lifespan is genuinely thought-provoking. Read as a blueprint for action, it requires more caution.