Posted on 18 November 2022
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Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.
Why is this research important: Researchers who study the ageing process view chronological age (the number of years since birth) as being distinct from biological age (the age the body ‘behaves as’ with the population average as a reference). You might be 60 years old, but if your cells and tissues behave like those of the average 50 year-old, you could be said to have a biological age of 50. Currently, the go-to method for measuring biological age is called a DNA methylation clock. This technique, of which there are multiple variants, involves measuring the presence of molecular ‘tags’ called methyl groups that are added to the DNA in order to change which genes are expressed. These tags are a type of epigenetic modification, and their presence changes throughout life, meaning they can be used to estimate how quickly someone is ageing at the cellular level.
Previous studies have shown that there is a pretty strong association between the strength of your muscles and your lifespan. People with weaker muscles are more likely to die from all causes than people with strong muscles. However, until recently, no one has studied whether this relationship extends to biological age.
What did the researchers do: In this study, researchers looked at data from 1274 middle aged and older adults who were followed up for 8 to 10 years. At the start of the study, researchers measured participants’ grip strength, which is a proxy for overall muscle strength and has previously been found to correlate well with reduced mortality. They then measured participants’ biological age using three different methylation clocks years later to see if grip strength could predict future biological age.
Key takeaway(s) from this research: After controlling for confounding factors such as smoking and sociodemographic factors, there was a significant association between higher grip strength and lower biological age for two out of three methylation clocks in men, and for all three clocks in women.
This doesn’t prove that weaker grip strength caused people to age faster – these people may have already been undergoing more rapid biological ageing because of other unaccounted factors, which could have been responsible for their weaker grip in the first place. Given what we know of the apparent benefits of strength training and the underlying mechanisms, it seems more likely than not that at least some of the differences in biological age were due to strength. To know this for sure, we’d need a randomised trial looking at biological age before and after a strength training intervention, which would be a long and costly endeavour.
As for how greater muscle strength could protect against ageing, lowering inflammation is a likely candidate. Chronic, low levels of inflammation throughout the body is a common driver of most age related diseases, and past research suggest that grip strength is linked to a reduction in such inflammation. There’s also evidence that larger muscles protect against resistance to the hormone insulin and diabetes, which also drive most age related diseases.
Ultimately, we care more about health outcomes than about biological age measurements, whose accuracy and relevance aren’t always clear. Having a low biological age is of small consolation if you have diabetes and are slowly dying from heart failure. However, it’s good to know that what we already knew about grip strength and health outcomes seems to align with what we believe to be a fundamental molecular process of ageing.
Grip strength is inversely associated with DNA methylation age acceleration: https://doi.org/10.1002/jcsm.13110
Is Muscle Weakness the New Smoking? Grip Strength Tied to Accelerated Biological Age: https://neurosciencenews.com/muscle-weakness-aging-21825/