Infiltration of skeletal muscle adipose tissue (myosteatosis) grows with age and is recognized as a key risk factor for cardiometabolic disorders. While visceral adiposity has been linked to dementia and cognitive decline, the link between myosteatosis and cognition is unknown. In comparison to White women, African-American women had more myosteatosis and a higher burden of Alzheimer’s Disease and Related Dementia. For a study, researchers sought to determine if myosteatosis was linked to cognitive performance in African Caribbean middle-aged and older women (ages 40-79).
The Health Study included information on 481 women. The Digit Symbol Substitution Test (DSST), a test of information processing speed, was used to assess cognition; the DSST is a rapid, reliable, and sensitive test that predicts the beginning of dementia. The DSST was administered to individuals by experienced interviewers, with scores ranging from 0 to 81. (lower score indicating cognitive decline). Calf skeletal muscle density (MD) was measured using Peripheral Quantitative Computed Tomography (Stratec XCT-2000), which served as a surrogate marker for myosteatosis (lower MD reflects more adiposity). Linear regression was performed to analyze the relationship between muscle density and cognition. It was controlled for age, education, muscle area, waist size, alcohol intake, smoking, walking hours, diabetes, and hypertension. The key predictor of interest (MD) results were standardized, with effects given per standard deviation (SD). The mean (standard deviation) DSST scores were 38.8. (13.2). Participants averaged 55.2 years old and had a BMI of 30.7 kg/m2. MD was 71.7((5.3) (mg/cm3) on average (SD). Unadjusted analyses revealed that older age and poorer education, larger waist circumference, diabetes, and hypertension were the main predictors of lower DSST scores in these women. We discovered that a one SD increase in MD was linked with a 1.48 rise in DSST score (p-value=0.015) after complete correction.
Our data imply that increased myosteatosis is related to poorer information processing speed in African Caribbean women, which may be an early predictor of future dementia risk. Future research using a broader battery of cognitive tests and long-term follow-up is needed to better understand the new role of myosteatosis in dementia risk in African-American women.