The study, which tracked thousands of different molecules in people aged 25 to 75, detected two major waves of age-related changes at around ages 44 and again at 60. The findings could explain why spikes in certain health issues including musculoskeletal problems and cardiovascular disease occur at certain ages.

“We’re not just changing gradually over time. There are some really dramatic changes,” said Prof Michael Snyder, a geneticist and director of the Center for Genomics and Personalized Medicine at Stanford University and senior author of the study.

“It turns out the mid-40s is a time of dramatic change, as is the early 60s – and that’s true no matter what class of molecules you look at.”

The research tracked 108 volunteers, who submitted blood and stool samples and skin, oral and nasal swabs every few months for between one and nearly seven years. Researchers assessed 135,000 different molecules (RNA, proteins and metabolites) and microbes (the bacteria, viruses and fungi living in the guts and on the skin of the participants).

I can't say I noticed anything at either of those points. It seemed pretty gradual to me until 70. The changes from 70-75 have been huge.