Ageing clocks can measure the biological age of people with high precision. Biological age can be influenced by environmental factors such as smoking or diet and can therefore deviate from chronological age, which is calculated based on the date of birth. The accuracy of these aging clocks suggests that the aging process follows a program. Scientists David Meyer and Professor Dr. Björn from the Cluster of Excellence Cellular Stress Responses in Aging-Associated Diseases (CECAD), an interdisciplinary research network at the University of Cologne, have now discovered that the aging clocks actually measure the increase in stochastic changes (random changes over time) in the cells. The study has been published in Nature Aging.

How Biological Ageing Clocks Tick

With increasing age, the control of the processes taking place in our cells becomes less effective, leading to more stochastic results. This is particularly evident in the accumulation of stochastic changes in DNA methylation. Methylation refers to the chemical changes that affect DNA, the building blocks of the genome. These methylation processes are strictly regulated in the body. However, random changes in the methylation patterns occur in the course of life. The accumulation of changes is a very accurate indicator of a person’s age.

The loss of control over the cells and the increase in stochastic variation is not limited to DNA methylation. Meyer and Schumacher show that the increase in stochastic variation can also be used as an aging clock in gene activity. Using the available data sets, the scientists showed that smoking increases random changes in humans, and that “anti-ageing” measures such as lower calorie intake in mice reduce the variation in methylation patterns. They also showed that the stochastic noise is even reversible by reprogramming somatic cells to stem cells. The scientists compared human fibroblasts from the skin that were reprogrammed to stem cells and rejuvenated as a result of reprogramming. The high fluctuation indicating the age of the somatic cells was actually reversed to the low stochastic noise of young stem cells.

The researchers hope that their findings on the loss of regulation and the accumulating stochastic changes will lead to new interventions that can address the cause of aging and even lead to cell rejuvenation. One target for such interventions could be the repair of stochastic changes in DNA or improved control of gene expression.

Study Shows Link Between Muscle Strength and Biological Age

Lifestyle choices such as diet and smoking, as well as disease, contribute to accelerating biological age beyond chronological age. In other words: Your body is aging faster than expected. And for the first time, researchers have found that muscle weakness, as evidenced by grip strength, which is a proxy for overall strength capacity, is associated with accelerated biological age. The weaker the grip strength, the older the biological age, according to results published in the Journal of Cachexia, Sarcopenia and Muscle. The results were obtained using “age acceleration clocks” based on DNA methylation, a process that is a molecular biomarker and an estimator of the rate of ageing. According to the researchers, grip strength could be used as a tool for early detection of functional decline, chronic disease and early mortality.

Everyone ages at a different pace. Therefore, two 50-year-olds can have different biological ages even though they are the same age. This means that a variety of internal and external factors have caused them to age at different rates and have a different risk of disease and early death. Michigan Medicine researchers led by Mark Peterson, Ph.D., M.S., lead author of the study and associate professor of physical medicine and rehabilitation at the University of Michigan, modeled the relationship between biological age and grip strength in 1,274 middle-aged and older adults using three “age acceleration clocks” based on DNA methylation, a process that is a molecular biomarker and estimator of the pace of aging. The clocks were originally modeled from various studies examining diabetes, cardiovascular disease, cancer, physical disability, Alzheimer’s disease, inflammation and early mortality. The results show that both older men and women showed a correlation between lower grip strength and biological age acceleration across DNA methylation clocks. This suggests that maintaining muscle strength across the lifespan can protect against many common age-related diseases. For example, smoking is known to be a strong predictor of disease and mortality, but it is now becoming clear that muscle weakness could be the new smoking.

Grip Strength as a Predictor of Chronic Disease and Early Mortality

Previous studies have already shown that low grip strength is an extremely strong predictor of adverse health events. In one study, it was even found to be a better predictor of cardiovascular events such as heart attacks than systolic blood pressure – the clinical feature used to detect heart disease. Peterson and his team have previously demonstrated a robust association between frailty and chronic disease and mortality in different populations.

This evidence combined with the recent results of their study, Peterson said, show the potential for clinicians to use grip strength as a way to screen individuals for future risk of functional decline, chronic disease and even early mortality. Screening for grip strength, the researchers say, would provide an opportunity to develop interventions that delay or prevent the onset or progression of these adverse age-related health events. In addition, Peterson said, studies need to focus on how lifestyle and behavioral factors such as physical activity and diet may affect grip strength and age acceleration.