Aging may not be the gradual process once thought, according to new research from Stanford University.

Led by the director of the Center for Genomics and Personalized Medicine, Michael Snyder, a study suggests significant physiological changes occur in people at around age 44 and again at age 60. The findings could shed light on why certain health issues, like musculoskeletal problems and cardiovascular disease, spike at specific ages.

“We’re not just changing gradually over time. There are some really dramatic changes,” Mr. Snyder said, according to the Guardian.

The research tracked 108 volunteers, aged 25 to 75, over several years, analyzing blood, stool samples, and swabs to assess more than 135,000 molecules and microbes. Surprisingly, the study found that molecular changes were not as steady as previously assumed. Instead, significant shifts were noted during two distinct age ranges — mid-40s and early 60s.

A former postdoctoral scholar at Stanford and lead author of the study, Xiaotao Shen, noted, “This suggests that while menopause or perimenopause may contribute to the changes observed in women in their mid-40s, there are likely other, more significant factors influencing these changes in both men and women.”

Two primary waves of changes were identified. The first, occurring in the mid-40s, included molecules related to cardiovascular health and the metabolism of caffeine, alcohol, and lipids. The second wave, detected in the early 60s, involved molecules tied to immune regulation, carbohydrate metabolism, and kidney function. Changes in molecules associated with skin and muscle aging were present in both periods.

The research aligns with existing evidence that age-related risks, such as those for Alzheimer’s and cardiovascular disease, do not increase steadily but rise sharply after 60. Some changes may also be linked to lifestyle factors, such as increased alcohol consumption during one’s 40s due to stress.