The research shows that the number of molecules and microorganisms in the body increases or decreases significantly between the ages of 40 and 60.
When assessing thousands of different molecules in people aged 25 to 75, as well as their microbiomes – the bacteria, viruses and fungi that live inside us and on our skin – scientists found that their numbers don't change gradually and chronologically.
Michael Snyder, chair of genetics at Stanford University in the US and lead author of the study, said: “We're not just changing gradually over time, there are really dramatic changes happening.
“It turns out that the mid-'40s is a time of dramatic change, just like the early '60s. And that's true no matter what class of molecules you're looking at.”
In people in their forties, significant changes were observed in the number of molecules related to alcohol, caffeine and fat metabolism, heart disease, and skin and muscle.
In people in their 60s, changes were related to carbohydrate and caffeine metabolism, immune regulation, kidney function, heart disease, and skin and muscle.
The researchers say some of these changes may be related to lifestyle or behavioral factors that occur in these age groups, rather than biological factors.
For example, a dysfunction in alcohol metabolism can result from increased alcohol consumption in people in their forties – an often stressful period in life.
But whatever causes these periods of change, their existence suggests that people should pay attention to their health during these times, the researchers said. That could mean exercising more to protect the heart and maintain muscle mass at both ages, or drinking less alcohol in their 40s, as the ability to process alcohol declines.
In the study, published in the journal Nature Agingthe researchers used data from 108 people they followed to better understand the biology of aging. The large cluster of changes in the mid-40s was surprising to the scientists.
At first, they thought menopause or perimenopause was the cause of the big changes in women. However, when they split the study group by gender, they found that the change was also happening in men in their mid-forties.