In terms of biological aging, the body seems to change gears three times during our life expectancy, research suggests in 2019 – with 34 years, 60 years and 78 years being the main thresholds.
In other words, there is evidence that aging is not a long, continuous process that moves at the same speed throughout our lives.
The findings can help us understand more about how our bodies start to decompose as we age, and how specific age-related diseases – including Alzheimer’s or cardiovascular disease – could be better fought.
The same study also presented a new way to safely predict people’s age using levels of protein (the proteome) in the blood.
“By deeply exploring the plasma proteome of aging, we identified undulating changes during human life,” wrote the researchers in their article, published in December 2019.
“These changes were the result of protein clusters moving in different patterns, culminating in the emergence of three waves of aging.”
The team analyzed blood plasma data from 4,263 people between the ages of 18 and 95, looking at the levels of about 3,000 different proteins that move through these biological systems and acting as a snapshot of what is happening in the body: of these, 1,379 were found to vary with age.
Although these protein levels often remain relatively constant, the researchers found that major changes occurred in the readings of various proteins around young adulthood (34 years old), middle age (60 years old) and old age (78 years old).
Why and how this is happening is still unclear; but if proteins can be traced back to their sources, this could allow a doctor, for example, to tell you that your liver is aging faster than that of a normal person.
It also emphasizes the link between aging and blood, something that has been detected in previous studies.
“We have known for a long time that measuring certain proteins in the blood can provide information about a person’s health – lipoproteins for cardiovascular health, for example,” said neurologist Tony Wyss-Coray of the Stanford Alzheimer’s Research Center (ADRC) at the time.
“But it has not been evaluated that so many different protein levels – about a third of all that we have examined – change markedly with advancing age.”
The researchers were able to establish a system by which the mixture of 373 selected proteins in the blood could be used to accurately predict someone’s age, by about three years or more.
Interestingly, when the system failed to predict a very young age, the individual was generally very healthy for his age.
Another finding from the study gives more evidence of something that has long been suspected: men and women age differently. Of the 1,379 proteins that changed with age, 895 (almost two-thirds) were significantly more predictive for one sex compared to the other.
These are still early discoveries – the researchers say any clinical application can still take five to 10 years – and much more work will be needed to find out how all of these proteins are markers of aging and whether or not they really contribute to it.
Still, it raises the possibility of one day having a blood test that can measure how well you are aging, at least at the cellular level.
And the more we know about aging, the more we can do to neutralize it. This could inform everything, from knowing what to drink and eat to potentially adding a few years to life, to identifying treatments to prevent some of the worst age-related illnesses.
“Ideally, you would like to know how virtually anything you have done or have done affects your physiological age,” said Wyss-Coray.
The research was published in Nature Medicine.
A version of this article was first published in December 2019.