THE ESSENTIAL
- The thickness and surface area of the temporalis muscle, located in the head and used to move the lower jaw, makes it possible to measure skeletal muscle loss.
- In older people with a small temporal surface area, the risk of dementia, more specifically Alzheimer’s disease, is 60% higher.
- A smaller sum of bilateral temporalis muscle cross-sectional areas also causes greater declines in the composite memory score, Functional Activity Questionnaire score, and structural brain volumes.
Connected to bones, skeletal muscles, which allow a wide variety of movements, make up about a third of a person’s total body mass. As adults age, they begin to lose it. This is particularly observed in seniors suffering from Alzheimer’s disease. In a recent study, researchers at Johns Hopkins University in Baltimore (United States) wanted to determine whether loss of the temporalis muscle was associated with an increased risk of dementia in older people. According to previous research, the thickness and surface area of the temporalis muscle, which is located in the head and serves to move the lower jaw, may be an indicator of muscle loss throughout the body.
Dementia: 60% risk in “elderly people with smaller skeletal muscles”
For the purposes of the work, American scientists analyzed brain scans in order to quantify muscle loss in 621 adults, aged on average 77 years, without dementia. The team manually segmented the bilateral temporalis muscles on the MRI images and calculated the sum of the cross-sectional areas of these muscles. Participants were classified into two distinct groups: large area muscles and small area muscles. During follow-up of approximately five years, the subsequent incidence of dementia, changes in cognitive and functional scores as well as changes in brain volume between the groups were examined.
According to the results, presented at the annual meeting of the Radiological Society of North America (RSNA), a smaller sum of the cross-sectional areas of the bilateral temporalis muscles was associated with a higher risk of the incidence of dementia, specifically Alzheimer’s disease. In addition, a small temporal surface area is related to a greater decrease in memory composite score, Functional Activity Questionnaire score, and structural brain volumes. “We found that older adults with smaller skeletal muscles are about 60% more likely to develop dementia after accounting for other known risk factors,” added Marilyn Albert, doctor of neurology and co-author of the study.
Measuring the thickness and area of the temporalis muscle, an indicator of the general condition of the muscles
Faced with these data, the authors emphasized that this muscular change could be analyzed during a conventional brain MRI, even when performed for other purposes, without incurring additional costs or burdens. “Interventions, such as physical activity, resistance training and nutritional support, could help prevent or slow muscle loss and, therefore, reduce the risk of cognitive decline and dementia,” said Shadpour Demehri, who participated in the work.
