The journey of a human throughout life can be perceived as a series of gradual transitions, beginning from conception and continuing until the end. However, if you find yourself gazing in the mirror one morning and questioning how you suddenly appear older, you might not be imagining it.

Recent studies focusing on the molecular transformations linked to aging indicate that individuals encounter two significant shifts: one typically around the age of 44 and another around 60 years old.

“Aging is not merely a smooth progression; it involves notable transitions,” expressed geneticist Michael Snyder from Stanford University, highlighting the study’s findings in August 2024.

“The mid-40s and early 60s are both periods of remarkable change, regardless of the type of biological molecules being examined.”

The complexity of aging is intertwined with increasing susceptibility to various diseases.

Snyder and his research team have been exploring the biology of aging to gain a deeper insight into the changes that occur, with the goal of finding ways to alleviate and treat age-related conditions.

As part of their research, they have been monitoring a group of 108 participants who have provided biological samples periodically over several years.

The team discovered that for certain conditions, including Alzheimer’s and cardiovascular disease, the increase in risk does not happen gradually but accelerates after reaching a specific age.

This prompted them to closely examine the biomarkers of aging to identify corresponding changes.

The researchers meticulously tracked various biomolecules from their participant samples, analyzing 135,239 biological features, including RNA, proteins, and microbiome compositions from gut, skin, nasal, and oral sources.

Each participant contributed an average of 47 samples over 626 days, with one participant providing 367 samples. This extensive data set generated over 246 billion data points, allowing the researchers to identify trends in molecular changes.

Previous investigations have indicated non-linear changes in molecular quantities related to aging in both rats and humans. Research involving fruit flies, mice, and zebrafish has also suggested a stepwise aging process in these species.

Snyder and his team observed marked variations in the concentration of various molecules in the human body occurring at two critical life stages. Notably, around 81 percent of the studied molecules exhibited changes during these periods, with peaks noted in the mid-40s and early 60s, reflecting somewhat differing profiles.

During the mid-40s peak, alterations in molecules associated with lipid metabolism, caffeine, alcohol, cardiovascular issues, and skin and muscle dysfunctions were detected. Meanwhile, the early 60s peak was linked to changes in carbohydrate metabolism, immune response, kidney function, and similar cardiovascular concerns.

The first peak, occurring in the mid-40s, coincides with the onset of menopause or perimenopause in women. However, researchers concluded that this hormonal transition is not the sole contributor, as men also exhibited significant molecular changes at this age.

“This implies that while menopause or perimenopause may play a role in the changes seen in women during their mid-40s, there are likely additional, more substantial influences affecting both genders,” commented metabolomicist and lead author Xiaotao Shen, now at Nanyang Technological University Singapore.

“Future research should prioritize identifying and examining these influential factors.”

The researchers acknowledge the small sample size and the limited biological variations tested, focusing on individuals aged 25 to 70. Future studies could explore this phenomenon in greater depth and across a broader demographic to enhance our understanding of how the human body evolves over time.

This research has been published in Nature Aging.

An earlier version of this article was released in August 2024.