Older adults who experience skeletal muscle loss may be at a significantly higher risk for developing Alzheimer’s disease (AD) dementia, according to new research presented at the annual meeting of the Radiological Society of North America (RSNA). The study suggests that people with greater muscle loss, measured in a muscle in the head that moves the lower jaw, face a 60% increased likelihood of developing AD dementia.
Skeletal muscle mass accounts for about one-third of a person’s total body weight and naturally declines as people age. In older adults, this loss is often linked to cognitive decline. This new study aimed to investigate whether muscle loss in the temporalis muscle, located on the head, could be used as a biomarker of a higher risk for AD.
“Measuring temporalis muscle size as a potential indicator for generalized skeletal muscle status offers an opportunity for skeletal muscle quantification without additional cost or burden in older adults who already have brain MRIs for any neurological condition, such as mild dementia,” said lead author Kamyar Moradi, MD, PhD, a postdoctoral research fellow at Johns Hopkins University School of Medicine.
The temporalis muscle is used for jaw movement and can be seen on brain MRI scans. Previous studies suggested that muscle thickness and area in this region might reflect overall skeletal muscle health, offering a noninvasive way to assess muscle loss throughout the body.
To determine this, the investigators of the study analyzed baseline brain MRI scans from a cohort of 621 participants without dementia in the Alzheimer’s Disease Neuroimaging Initiative (ADNI), a multicenter, longitudinal, observational study with a goal of identifying and validating clinical biomarkers of AD to aid in clinical trials. The researchers manually measured the cross-sectional area (CSA) of the temporalis muscles from the MRI scans and divided participants into two groups: those with a large CSA and those with a small CSA. The study followed the participants for an average of 5.8 years, during which the researchers assessed cognitive scores, functional activity, brain volume, and the incidence of AD dementia.
The researchers’ analysis found that a smaller temporalis CSA was associated with a higher risk of AD dementia and, further, this was also associated with greater decreases in memory composite scores, functional activity questionnaire scores, and brain volume of the 5.8 year follow-up periods.
“We found that older adults with smaller skeletal muscles are about 60% more likely to develop dementia when adjusted for other known risk factors,” said co-senior author Marilyn Albert, PhD, a professor of neurology at Johns Hopkins.
The researchers noted that their findings show that measuring any changes in the temporalis muscle can be opportunistically used to assess potential AD dementia risk via brain MRIs, even those conducted for other purposes without increasing medical costs or patient burden. Such early identification of muscle loss could suggest health interventions such as physical activity, resistance training, and nutritional support strategies that could help slow muscle deterioration and, in turn, reduce the risk of cognitive decline and dementia.
