- A new study builds on existing evidence suggesting that grip strength is a biomarker of their biological age.
- According to researchers, grip strength aligns with epigenetic clocks that assess the age of a person’s DNA.
- Grip strength is an indicator of overall muscle strength, a lack of which has been implicated in accelerated aging.
Chronological age is different from biological age since it encompasses the amount of time that has passed between birth and a given date.
Biological age refers to the rate at which your body is actually aging, which may depend on a host of variables, including genetics, behavior, the environment in which you live, and your demographic identity.
Rather than focusing on age in terms of how many years have passed since birth, experts are investigating aging biomarkers that can help assess more accurately how an individual is aging. The goal is to gain clearer insights to help people, where possible, proactively manage their current or imminent health issues and predict longevity.
A new study from researchers at the University of Michigan’s Michigan Medicine in Ann Arbor, MI, provides new evidence that grip strength in a person’s hands is one such biomarker of biological age.
The study found an association between low grip strength weakness and accelerated DNA aging.
The study’s lead author, Mark D. Peterson, Ph.D. associate professor of physical medicine and rehabilitation research at Michigan Medicine, explained to Medical News Today:
“Grip strength has long been considered a biomarker of aging. However, very few studies have tried to understand the biological mechanism(s) that link weakness with negative health outcomes (including mortality). On the positive side, it is likely that greater grip strength is associated with lifestyles such as exercise and healthy dietary habits. On the negative side, it is likely that weaker grip strength is associated with obesity-related chronic conditions, other noncommunicable diseases, and sedentary lifestyles.”
The study was recently published in the Journal of Cachexia, Sarcopenia and Muscle.
Measuring age with DNA methylation clocks
The researchers investigated the correlation between low grip strength and DNA methylation, or DNAm, a process that affects the expression of genes.
In methylation, a methyl chemical group consisting of one carbon and three hydrogen atoms is added to one of DNA’s four main chemicals, cytosine.
At locations in the body called CpG-sites, methylation levels decrease over the course of a person’s life and thus represent a way of assessing biological age.
Dr. Elina Sillanpää, Ph.D., associate professor at the University of Jyväskylä in Vuokatti, Finland, and expert in quantitative genetics and biological aging, not involved in the current study, has previously investigated the use of DNAm as an indicator of aging.
“In our studies, we have used DNAm-based algorithms that summarize methylation levels at specific CpG-sites and produce an estimate of a person’s biological aging pace,” she told MNT. “These methylation changes correlate clockwise with aging or are associated with lifestyle factors.”
“You may describe that biological aging pace measured using these algorithms — called ‘epigenetic clocks’ — summarizes the cumulative burden of your previous lifestyles and environmental hazards, but also reflect the genetics behind. CpG sites included into the epigenetic clocks associate with classical hallmarks of aging.”
– Elina Sillanpää, Ph.D., biological aging and genetics researcher
Dr. Peterson added that epigenetic phenomena, such as DNA methylation, are highly implicated in the rate of biological aging and the development of chronic disease.
“Given that methylation profiles are modifiable by lifestyle and other environmental factors, it has been proposed that DNAm age is a robust biological aging clock, providing a superior estimate of true biological age over chronological age,” Dr. Peterson said.
Comparing grip strength to 3 epigenetic clocks
The new study compared grip strength values to three epigenetic clocks, the algorithms of which are trained on various health outcomes.
According to Dr. Peterson, PhenoAge uses “composite clinical biomarkers combined into a multi-system measure of biological age,” which was “developed to estimate an individual’s mortality risk using markers of tissue and immune function and age.”
He said that PhenoAge has a demonstrated ability to predict multiple aging outcomes such as:
- physical function
- Alzheimer’s disease
Dr. Peterson explained that GrimAge is trained on “surrogate DNAm biomarkers of physiological risk and stress factors,” combined with a measurement of smoking years to estimate a composite biomarker of a person’s lifespan.
“High values of this measure are associated with morbidity and mortality risk,” he added.
Dr. Peterson explained that the third epigenetic clock, DunedinPoAm, tracks 18 biomarkers that measure the rate of aging in the following physiological systems:
- immune system
A strong link between grip strength and aging
The researchers analyzed data from 1,275 individuals participating in the longitudinal Health and Retirement Study(HRS).
Participants were 50 and over in 2006 and 2008 when data collection began, followed for 8–10 years by the HRS. Interview transcripts, grip strength data, and biological measurements were available for all of them.
Methylation values were collected from 4,018 of these participants in the 2016 Health and Retirement Venous Blood Study.
The analysis revealed that decreasing grip strength aligned strongly with all three of the clocks, although there were differences between men and women.
“The association between muscle strength and epigenetic aging is likely related to the mechanisms regulating general health,” Dr. Sillanpää said.
Dr. Peterson noted: “We have recently also demonstrated that muscle weakness and testosterone deficiency were highly correlated and independently associated with multi-morbidity in young and older men.”
“In our current study, there seemed to be a more pronounced/robust cross-sectional association [a comparison of a population] between lower grip strength and age acceleration in men. However, the opposite was true for the longitudinal association [a comparison over time], which was more pronounced/robust among women. We cannot speculate what is driving that difference.”
– Mark D. Peterson, Ph.D., lead author of the study
Could improving grip strength help you live longer?
MNT asked Dr. Peterson if people should focus on developing grip strength based on this study:
“No, there is no plausible reason to suspect that increasing grip strength alone would lead to increases in health or longevity,” he said.
“Grip strength is a proxy indicator of overall muscle strength, meaning that it is highly correlated to other measures of strength. Thus, simply increasing grip strength would not render any changes to health or longevity.”
Still, weak muscles overall may accelerate the aging process in some individuals.
Dr. Peterson noted that activities that improve overall strength capacity and promote healthy weight maintenance are well-known drivers of healthy aging and longevity. Such lifestyle interventions include:
- aerobic exercise
- strength training
- healthy dietary habits
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