Intramuscular fat and physical performance at the Framingham Heart Study

Abstract

Intramuscular fat may mediate associations between obesity and physical disability. We examined the associations between muscle attenuation, a proxy for intramuscular fat, and physical function. Paraspinous muscle computed tomography attenuation was obtained on a Framingham Heart Study subgroup (n = 1152, 56 % women, mean age 66 years). Regressions modeled cross-sectional associations between muscle attenuation and mobility disability, grip strength, and walking speed with standard covariates; models additionally adjusted for body mass index (BMI) and visceral adipose tissue (VAT). Separate models investigated associations between VAT and subcutaneous adipose tissue (SAT) and physical function. Per 1 standard deviation decrement in muscle attenuation (i.e., more muscle fat), we observed 1.29 (95 % CI = 1.11, 1.50; p = 0.0009) increased odds of walking speed ≤1 m/s in women and men. This persisted after separate BMI and VAT adjustments (p < 0.02). In men, there was a 1.29 kg (95 % CI = 0.57, 2.01; p = 0.0005) decrement in grip strength, which persisted after BMI and VAT adjustments (p ≤ 0.0004). For VAT and SAT, similar associations were not observed. Intramuscular fat is associated with increased odds of walking speed ≤1 m/s in both sexes and lower grip strength in men. There were no similar associations for VAT and SAT, highlighting the specificity of intramuscular fat in association with physical function.

Keywords: Adipose tissue; Epidemiology; Muscle; Physical function.

Fig. 1

Percentage of participants in each muscle attenuation tertile group (tertile 1—lowest muscle attenuation, i.e., greatest amount of intramuscular fat up to tertile 3—highest muscle attenuation, i.e., least amount of intramuscular fat) who have a walking speed of ≤1 m/s; n = 1152. *Test for trend in each case had p value < 0.0001 **Tertiles ranging from tertile 1 (lowest muscle attenuation, i.e., most intramuscular fat) to tertile 3 (highest muscle attenuation, i.e., least intramuscular fat)