a growing number of scientists are questioning our basic conception of aging. What if you could challenge your death—or even prevent it altogether? What if the panoply of diseases that strike us in old age are symptoms, not causes? What would change if we classified aging itself as the disease?
in 2016, a high-profile study published in Nature argued that human life has a hard limit of about 115 years. This estimate is based on global demographic data showing that improvements in survival with age tend to decline after 100, and that the record for human longevity hasn’t increased since the 1990s. Other researchers have disputed the way the analysis was done.
Biomarkers that can identify biological age are a popular tool in aging research, says Vadim Gladyshev of Brigham and Women’s Hospital in Boston. He characterizes aging as the accumulation of deleterious changes across the body, ranging from shifts in the populations of bacteria that live in our gut to differences in the degree of chemical scarring on our DNA, known as methylation. These are biological measures that can be tracked, so they can also be used to monitor the effectiveness of anti-aging drugs.
Barzilai is leading a human trial called TAME (Targeting Aging with Metformin) that plans to give the drug to people aged 65 to 80 to see if it delays problems such as cancer, dementia, stroke, and heart attacks. Although the trial has struggled to raise funding—partly because metformin is a generic drug, which reduces potential profits for drug companies—Barzilai says he and his colleagues are now ready to recruit patients and start later this year.
Metformin is one of a broader class of drugs called mTOR inhibitors. These interfere with a cell protein involved in division and growth. By turning the protein’s activity down, scientists think they can mimic the known benefits of calorie restriction diets. These diets can make animals live longer; it’s thought that the body may respond to the lack of food by taking protective measures. Preliminary human tests suggest the drugs can boost older people’s immune systems and stop them from catching infectious bugs.
Reclassifying aging as a disease could have another big benefit. David Gems, a professor of the biology of aging at University College London, says it would provide a way to crack down on quack anti-aging products. “That would essentially protect older people from the swirling swamp of exploitation of the anti-aging business. They’re able to make all sorts of claims because it’s not legally a disease,” Gems says.