Q&A: Grip strength screenings could identify patients at risk for functional decline

Lower grip strength was associated with faster biological aging among men and women, a recent study published in the Journal of Cachexia, Sarcopenia, and Muscle found.

“We’ve known that muscular strength is a predictor of longevity, and that weakness is a powerful indicator of disease and mortality, but, for the first time, we have found strong evidence of a biological link between muscle weakness and actual acceleration in biological age,” Mark Peterson, PhD, MS, an associate professor of physical medicine and rehabilitation at the University of Michigan, said in a press release.

Using Health and Retirement Study data from 2006 to 2008, Peterson and colleagues examined associations between grip strength and three measures of DNA methylation (DNAm) age acceleration: the DunedinPoAm, PhenoAge and GrimAge clocks.

The final study group consisted of 1,275 participants with a mean age of 70 years. Of the group, 45.9% of men and 43.7% of women were classified as obese.

Over an 8- to 10-year follow-up period, the researchers found significant associations between normalized grip strength (NGS) and all three DNAm age acceleration clocks in men, as well as significant associations using DunedinPoAm and GrimAge clocks in women.

In addition, Peterson and colleagues reported an independent longitudinal association between baseline NGS and DNAm in men (P < .001) and women (P < .001) using the DunedinPoAm clock, and in women only, the PhenoAge (P < .001) and GrimAge (P < .001) clocks.

“This suggests that if you maintain your muscle strength across the lifespan, you may be able to protect against many common age-related diseases,” Peterson said.

Healio spoke with Peterson to learn more about the study findings, how grip strength could be utilized as a screening tool in a primary care setting, and what future research should focus on.

Healio: What drew you to conduct this study?

Peterson: Individuals who are weaker, as measured by grip strength, are known to be at high risk for everything from disability to cardiovascular disease to diabetes to cognitive decline and dementia — even early all-cause and cardiovascular mortality. It has always been considered a biomarker of aging, but nobody has ever attempted to figure out exactly why, in terms of a mechanism, what are the biological or physiological mechanisms linking low grip strength and poor health outcomes, or high grip strength and positive health outcomes.

This study is something I’ve wanted to do for a very long time, to look if there’s a relationship between measures of grip strength and what we are now calling biological aging. Using DNA methylation clocks, we can look at the extent to which people age at different paces, and in this case, we use grip strength as the exposure variable of interest and look at completely different accelerated aging clocks.

Healio: How could grip strength translate to clinical screenings?

Peterson: That’s one of the most important takeaways. It’s being done in geriatrics very often to look at things like cancer cachexia and also in other malnutrition patients. But in terms of a screening tool in primary care, it’s not being done very often or at all. My personal opinion is if it’s that strong of a predictor — and it’s even a better predictor of cardiovascular mortality than blood pressure — I feel it deserves a place in clinical screening.

There are benchmark levels of strength by which we could say is weak or not weak, and there is also the ability to screen someone over the course of time to see if there’s changes in strength, and changes in strength are very strong predicators of poor outcomes as well.

Healio: Why are clinicians not utilizing these kinds of screenings?

Peterson: The list of standard clinical care is, when it comes to screening, vital exams like blood pressure, height and weight. Nobody’s really looking at physical function. In this case, this is a screening tool that gets at muscular strength, but it’s highly associated with [areas] like disability and multiple organ system health.

When you take somebody’s blood pressure, you know exactly what that is. That is the pressure that builds up in the heart to the rest of the body. But when you take a grip strength measure, somebody would say, ‘So are you telling me I just need to improve my grip strength, and that will help me to live longer?’ That’s why it’s confusing. The answer to that question is definitely not — it’s an indication that somebody should be doing more healthy lifestyles that will improve overall strength and robustness.

It’s a nebulous biomarker of poor health from top to bottom. We’re pushing hard on the literature to get this message out, because it is an extraordinarily robust predicator, but if you were to ask a doctor, they would say, ‘What am I support to tell a patient if their grip strength is low?’ because it’s not a medical diagnosis.

That’s the reason why it hasn’t, but that does not mean that it doesn’t have an extremely high clinical value for helping patients to improve their lives and health.

Healio: Where does research go from here?

Peterson: Future research should try to understand the specific biological links for males versus females. We found disparate information between men and women, and the role of strength capacity in health outcomes has a strong sex-specific pattern, because men tend to be stronger yet die younger than woman for various reasons.

Women tend to have higher risk for frailty and conditions like osteoporosis and osteopenia, so the signature that preservational strength plays seems to be strongly associated with sex.

Some of the other biomarkers that might be of interest would be inflammatory markers that are known to increase in age and disease, which are also hallmarks of frailty and early mortality.

References:

• Is weakness the new smoking? Muscle strength tied to biological age, study shows. https://labblog.uofmhealth.org/body-work/muscle-weakness-new-smoking. Published Nov. 10, 2022. Accessed Dec. 5, 2022.
• Peterson M, et al. J Cachexia Sarcopenia Muscle. 2022;doi:10.1002/jcsm.13110.