These two ages are turning points in our aging process

On paper, we age gradually, year after year. But is it really that simple? Our bodies age significantly at two very specific ages. Researchers at Stanford University in San Francisco have just shown that, biologically, we start to age at around 44 and then 60. “It turns out that the mid-40s are a time of dramatic change, as are the early 60s. And that's true whatever class of molecules we're studying,” said Michael Snyder, professor of Genetics at Stanford Medical School and lead author of the study published in the journal Nature Aging.Researchers collected blood, stool and bacteria samples from the skin, mouth and nose of 108 California residents aged 25 to 75, every three months for almost two years. In total, 5,405 biological samples were collected and 135,239 biological characteristics were acquired, generating “more than 246 billion data points,” the study stated. The researchers then analyzed, according to the age of the subjects, a wide range of cells, molecules, microbes, proteins and metabolites, as well as the bacteria present in the participants' microbiomes. The scientists then brought to light a “particularly intriguing” result: The abundance of most molecules and microbes does not change in a progressive, chronological manner. “Only a small fraction of molecules (6.6%) showed linear changes throughout human aging,” they wrote.Conversely, 81% of molecules evolved at specific life stages, with particularly significant changes around the ages of 44 and 60. “This non-linear trend was observed across all omics data types with remarkably high consistency,” they pointed out.Wrinkles and grey hairIn detail, the number of molecules linked to cardiovascular disease shows significant changes at both ages, while those linked to immune function change in the early 60s. In subjects in their 40s, the researchers observed changes in the number of diseases linked to alcohol, caffeine and lipid metabolism, cardiovascular disease, skin and muscle; a probable coincidence with the appearance of the first wrinkles, the first grey hairs, but also a certain drop in energy. In the sexagenarians, the differences tended to concern carbohydrate and caffeine metabolism, immune regulation, kidney function, cardiovascular disease, skin and muscle.While they thought that women would be more affected by these upheavals due to perimenopause, results for men were similar. “This suggests that while menopause or perimenopause may contribute to the changes observed in women in their mid-40s, there are probably other, more important factors influencing these changes in both men and women,” observed Xiaotao Shen, postdoctoral researcher in medicine at Stanford University and first author of the study.Hypotheses to be confirmedHowever, “It is possible that some of these changes are linked to lifestyle or behavioural factors that are concentrated in these age groups, rather than biological factors,” the researchers said. For example, a dysfunction in alcohol metabolism could be due to an increase in alcohol consumption in the mid-40s, a period when people may be going through the notorious “mid-life crisis.”To get a clearer picture, the scientists plan to explore the various possible factors in the future, and above all to refine their analyses by enlarging and diversifying their cohort, since the 108 participants they recruited lived mainly in the vicinity of Stanford University. They therefore belonged to a community of individuals with average-to-high incomes, which is not representative of other populations. In the meantime, these results demonstrate the importance of taking care of one’s health, especially in one's 40s and 60s, whether by increasing physical activity, reducing alcohol consumption or changing one's diet, they concluded.This article has been translated from its original French and was first published by our sister publication Profession Santê.

These two ages are turning points in our aging process

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