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The relationship between muscle mass, cognitive health, and dementia risk in older adults

Edith Cowan University researchers in Australia have suggested that grip strength and mobility tests may indicate if older people are at risk of developing dementia. While muscle loss is a well-known problem for aging individuals, new research suggests that the decline in muscle strength may be a sign of developing dementia. Researchers used grip strength and mobility tests to evaluate muscle function in a group of women aged 75 and above, with data from the Perth Longitudinal Study of Ageing in Women. The study shows that lower grip strength and slower Timed Up and Go (TUG) tests were significant risk factors for developing dementia. Women with the weakest grip strength and slowest TUG tests were more than twice as likely to have a dementia event later in life. The study was published in the Journal of Cachexia Sarcopenia and Muscle.

Dr. Marc Sim, senior research fellow in the Nutrition & Health Innovation Research Institute at Edith Cowan University and lead author of the study, explains that there are strong links between physical capacity, including muscle mass and cognitive health. He suggests that grip strength and TUG tests can serve as a screening tool for clinicians to identify those most at risk and enable the promotion of primary prevention strategies, such as exercise and nutrition. Screening for dementia risk at the community level is rarely performed.

The TUG test is used to check mobility and balance. A person is asked to sit in a normal chair, and as a medical professional times them with a stopwatch, the person is asked to stand up, walk to a line about 10 feet away from the chair, turn around, walk back to the chair, and sit back down in the chair. This allows the doctor to see how the person is walking and check their movement for postural or balance issues.

Grip strength has long been considered a biomarker of a person’s overall health. Doctors administer a grip strength test when they want to measure the muscle health of a person’s hands and forearms. This simple test uses a tool called a dynamometer. The person holds the dynamometer in their hand and squeezes it with all their strength, and the tool measures the amount of force used.

The researchers used grip strength and TUG tests as their methods to analyze study participants’ muscle function because they are both simple and easy to perform and are currently recommended as functional tests as part of sarcopenia criteria in Australia. There is very strong evidence for these tests to predict a range of adverse outcomes in older populations, such as falls, fractures, cardiovascular disease, and mortality.

The study used data from over 1,000 women with an average age of 75. Researchers administered grip strength and TUG tests to each woman, which were repeated five years later. The scientists found that over the next 15 years, about 17% of study participants either had a dementia event that was either a dementia-related hospitalization or death.

This was independent of other risk factors such as smoking, alcohol use, and physical activity levels. Dr. Sim commented that people who struggle with daily activities of living due to physical limitations are less likely to engage in exercise, which is a major risk factor for dementia. The high dementia risk associated with declining function over five years, where those with the greatest decline were at the highest risk, is an important point for clinicians to consider.

Dr. Raphi Wald, a board-certified neuropsychologist at Marcus Neuroscience Institute, established at Boca Raton Regional Hospital part of Baptist Health South Florida, who was not involved in the study, explains that the study is helpful in confirming what we knew and strongly suspected about declining strength and cognitive functioning. He adds that there are a number of often subclinical signs and symptoms of dementia that pop up before serious deterioration begins.