Feeling like everything in your body seems to be deteriorating at once? You might not be imagining it if you're at a certain point in your 40s or 60s.
It's often been the belief that your body starts to steadily age right as you're finished growing and maturing. But a new study says that instead of aging being a linear, gradual process, it comes with at least two massive bursts, hitting humans at the average ages of 44 and 60 and often bringing along negative health impacts.
Stanford Medicine researchers came to this conclusion after tracking the levels of more than 135,000 different molecules and microbes in 108 people, aged 25 to 75, for one to nearly seven years. During this time, the researchers gathered blood and stool samples and skin, oral and nasal swabs from the participants every three to six months to test for age-related changes in their molecular profiles.
The results, published in the journal Nature Aging, revealed that the amount of molecules and microbes in the body don't change steadily or chronologically. Rather, humans go through two periods in which these dramatically change in abundance, first at around age 44 and the next at age 60.
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Researchers said that the shift at age 60 wasn't too surprising, as it's known that many age-related disease risks increase at that point in life, but the cluster of change in the mid-40s was a new discovery.
Though at first the scientists thought the number might be related to the average menopausal age for women — which is between 45 and 55 — they later found that the shift happens for men at the same time.
"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. Identifying and studying these factors should be a priority for future research," said Dr. Xiaotao Shen, the study's first author.
At the mid-40s aging burst, the study showed significant changes in the levels of molecules linked to skin and muscle, cardiovascular disease and the ability to metabolize alcohol, caffeine and lipids. Then at the 60-year aging burst, researchers also found molecular shifts linked to skin and muscle, cardiovascular disease and caffeine metabolism. But there were also changes linked to immune regulation, kidney function and carbohydrate metabolism.
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The researchers noted that some of these biological shifts could be tied to lifestyle or behavioral changes: If a person in their mid-40s is consuming more alcohol, they could see a shift in their alcohol metabolism function, for example. But they say this indicates a need for more exploration into why these clusters change.
In any case, the scientists say the existence of the two aging bursts suggests people should pay closer attention to their health, particularly at those two ages. Useful habits could include maintaining muscle mass, keeping your heart and weight healthy, reducing alcohol and caffeine in your mid-40s and more.
"I'm a big believer that we should try to adjust our lifestyles while we're still healthy," said Dr. Michael Snyder, the study's senior author.