Abstract MP77: Intramuscular Fat is Associated with Decreased Physical Performance
Introduction: Obesity is associated with a substantial burden of physical disability. Intramuscular fat may in part mediate some of these associations.
Hypothesis: We hypothesized that muscle attenuation, an estimation of intramuscular fat, is associated with increased mobility disability, as well as decreased grip strength and walking speed, two physical performance measures associated with functional decline.
Methods: The sample (n=1152, 56% women, mean age 66 years) consisted of Framingham Heart Study participants who underwent computed tomography scanning and an examination in 2005-2008. Muscle attenuation was estimated from scans by placing regions of interest on the paraspinous muscles bilaterally and averaging the resulting Hounsfield units. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were measured using standard protocols. Hand grip strength was measured with a handheld dynamometer bilaterally, walking speed was measured over a 4 m course, and mobility disability via self-report of inability to walk half a mile or climb a flight of stairs. Multivariable logistic and linear regression models were used to investigate the association between muscle attenuation and mobility disability, grip strength, and walking speed after accounting for standard covariates; models additionally adjusted for body mass index (BMI) and VAT volume separately. Additional models were used to investigate the association between VAT and SAT volumes and mobility disability and physical performance measures.
Results: Mean BMI was 28.3 kg/m2, average walking speed was 1.23 m/s, and average grip strength was 31.9 kg. Per 1 standard deviation decrease in muscle attenuation (i.e. more muscle fat), we observed a 1.29 (95% CI 1.09 – 1.53, p=0.0009) increased odds of walking speed ≤ 1 m/s, a cutoff associated with increased mortality. This persisted even after adjustment for BMI and VAT volume separately (p<0.02). In men only (sex interaction p<0.0001), there was a 1.29 (95% CI 0.46 – 2.12, p=0.0005) kg decrease in grip strength, which persisted after adjustment for BMI and VAT volume separately (p≤0.0004). No associations were observed with mobility disability. For VAT and SAT volumes, no associations with grip strength (p≥0.19) were observed. Furthermore, no associations with walking speed ≤ 1 m/s were observed after adjustment for BMI (p≥0.18).
Conclusion: Intramuscular fat is associated with increased odds of walking speed ≤ 1m/s in both sexes and decreased grip strength in men, associations which persist after adjustment for VAT volume and BMI. Similar associations for VAT and SAT volumes were not observed. These findings highlight the specificity of intramuscular fat and important indices of physical performance.
Author Disclosures: K.E. Therkelsen: None. A. Pedley: A. Employment; Modest; Merck pharmaceuticals. U. Hoffman: None. C. Fox: None. J. Murabito: None.
- © 2015 by American Heart Association, Inc.