For just over five years, Bryan Johnson has been spending more than $2 million a year trying not to die. The American technology millionaire has turned his body into an elaborate — or, depending on your perspective, recklessly extravagant — experiment in human longevity, subjecting himself to extensive medical testing, controlled nutrition, rigid sleeping schedules, and experimental interventions. At forty-nine, he employs an entire medical team to scrutinize the smallest changes in his physiology. A whole ecosystem is organized around preserving his health, with varying degrees of success. In July of this year, he announced that he had been diagnosed with an incurable autoimmune gastritis.

Millions of people share a distantly related version of Johnson’s ambition. But rather than living forever, they would simply like to reach retirement without being debilitated by chronic illness. There is something revealing about a society in which even biological certainty has a class dimension. Although the wealthy are devoting millions to preventing the deterioration of their bodies, for much of the population, the prospect of growing old in reasonable health is a luxury.

We have long understood that poverty shortens lives. A growing body of gerontological research now suggests that disadvantage may also accelerate the biological processes by which people grow old.