Like any typical car or house or society, the pace at which parts of the human body fall apart varies from part to part.
A study of 5,678 people, led by Stanford Medicine investigators, has shown that the human organs age at different rates, Stanford Medicine informed.
According to the study, about 1 in every 5 reasonably healthy adults 50 or older is walking around with at least one organ aging at a strongly accelerated rate.
The silver lining: It may be possible that a simple blood test can tell which, if any, organs in a person’s body are aging rapidly, guiding therapeutic interventions well before clinical symptoms manifest.
Biological versus chronological age
Using commercially available technologies and an algorithm of their own design, the researchers assessed the levels of thousands of proteins in people’s blood, determined that nearly 1,000 of those proteins originated within one or another single organ, and tied aberrant levels of those proteins to corresponding organs’ accelerated aging and susceptibility to disease and mortality.
They started by checking the levels of nearly 5,000 proteins in the blood of just under 1,400 healthy people ages 20 to 90 but mostly in mid- to late stages of life, and flagging all proteins whose genes were four times more highly activated in one organ compared with any other organ. They found nearly 900 such organ-specific proteins, which they whittled down to 858 for purposes of reliability.
To do this, they trained a machine-learning algorithm to guess people’s age based on the levels of those nearly 5,000 proteins.
The scientists verified the algorithm’s accuracy by assessing the ages of another 4,000 or so people who were somewhat representative of the U.S. population.
Organ age gap
For each of the 11 organs, the team this study’s senior author, Tony Wyss-Coray, PhD, a professor of neurology, came up with an “age gap”: the difference between an organ’s actual age and its estimated age based on the algorithm’s organ-specific-protein-driven calculations. The researchers found that the identified age gaps for 10 of the 11 organs studied (the only exception being intestine) were significantly associated with future risk of death from all causes over 15 years of follow-up.
Having an accelerated-aging organ (defined as having a 1-standard-deviation higher algorithm-scored biological age of the organ than the group average for that organ among people of the same chronological age) carried a 15% to 50% higher mortality risk over the next 15 years, depending on which organ was affected.
People with accelerated heart aging but initially exhibiting no active disease or clinically abnormal biomarkers were at 2.5 times as high a risk of heart failure as people with normally aging hearts, the study showed.
Those with “older” brains were 1.8 times as likely to show cognitive decline over five years as those with “young” brains. Accelerated brain or vasculature aging—either one—predicted risk for Alzheimer’s disease progression as well as the best currently used clinical biomarkers do.
There were likewise strong associations between an extreme-aging (more than 2 standard deviations above the norm) kidney score and both hypertension and diabetes, as well as between an extreme-aging heart score and both atrial fibrillation and heart attack.
Identifying the organ-specific proteins that best indicate excessive organ aging and, consequently, elevated disease risk could also lead to new drug targets, said Tony Wyss-Coray.