- A study finds that biological aging is linked to both mental and physical health.
- Factors consistently related to advanced biological aging include: being male, smoking, being overweight, and having depression.
- The researchers found that depression is linked to more advanced biological aging.
- Combining aging measures from multiple cellular levels best captures biological age.
Our chronological age, of course, is what we celebrate with each passing birthday. But people who are the same chronological age may not be aging at the same rate.
Scientists are using biology to more accurately measure how quickly humans age.
One factor is the length of an individual’s telomeres, stretches of DNA and proteins at the ends of our chromosomes that shorten as we age. An epigenetic clock, meanwhile, looks at the changes in gene function that do not make alterations to the genetic code, or genome.
Another aging clock is based on transcriptomes, a collection of all the gene readouts in a cell. Scientists also measure age with metabolomics, the study of the chemical processes that involve metabolites, small molecules produced by and during metabolic processes.
In addition, scientists use what they call a proteomic clock, which measures levels of proteins in the blood.
For a new study, now published in the journal eLife, researchersset out to learn whether a composite biological clock outperforms individual biological clocks in predicting health.
“To develop a better understanding of the mechanisms underlying biological aging, we wanted to examine how indicators of biological aging relate to each other, how they link to determinants of physical and mental health, and whether a combined biological clock, made up of all age indicators, is a better predictor of health,” says co-lead author Dr. Rick Jansen, an assistant professor in the department of psychiatry at Amsterdam UMC, in the Netherlands.
The researchers used blood samples from 2,981 individuals aged 18–65 years who took part in the Netherlands Study of Depression and Anxiety. Of the participants, 74% had a diagnosis of a depressive disorder, an anxiety disorder, or both, while 26% were healthy control participants.
The participants were recruited from medical facilities and the general population between September 2004 and February 2007.
The team used computer modeling to examine whether five measures of biological aging — telomere length and the epigenetic, transcriptomic, proteomic, and metabolomic clocks — were interrelated and associated with mental and physical health.
The researchers then took the five indicators and incorporated them into an analysis that also included sex, lifestyle factors, physical ability, and known health conditions.
The scientists found that being male was associated with more advanced biological aging according to four of the five biological clock measurements. This is consistent with the understanding that in most places, women outlive men.
Other factors associated with more advanced biological aging according to at least four of the five measures were: having a high body mass index, smoking, and having metabolic syndrome.
The researchers also discovered that depression is linked to more advanced biological aging.
In addition, they noted associations between medication use and this aging. However, they could not determine whether this was due to the medication itself or the underlying physical or mental illness requiring treatment.
Meanwhile, the study allowed the researchers to infer that some biological clocks show overlap, but most seem to be tracking different aspects of the aging process.
They write:
“This provides further support for the hypothesis that not one biological clock sufficiently captures the biological aging process and that not all clocks are under the control of one unitary aging process.”
The study is part of a special issue of eLife about longevity.