Sarcopenia, sarcopenic obesity and mortality in older adults: results from the National Health and Nutrition Examination Survey III.

BACKGROUND: Sarcopenia is defined as the loss of skeletal muscle mass and quality, which accelerates with aging and is associated with functional decline. Rising obesity prevalence has led to a high-risk group with both disorders. We assessed mortality risk associated with sarcopenia and sarcopenic obesity in elders.

METHODS: A subsample of 4652 subjects ≥60 years of age was identified from the National Health and Nutrition Examination Survey III (1988-1994), a cross-sectional survey of non-institutionalized adults. National Death Index data were linked to this data set. Sarcopenia was defined using a bioelectrical impedance formula validated using magnetic resonance imaging-measured skeletal mass by Janssen et al. Cutoffs for total skeletal muscle mass adjusted for height(2) were sex-specific (men: ≤5.75 kg/m(2); females ≤10.75 kg/m(2)). Obesity was based on % body fat (males: ≥27%, females: ≥38%). Modeling assessed mortality adjusting for age, sex, ethnicity (model 1), comorbidities (hypertension, diabetes, congestive heart failure, osteoporosis, cancer, coronary artery disease and arthritis), smoking, physical activity, self-reported health (model 2) and mobility limitations (model 3).

RESULTS: Mean age was 70.6±0.2 years and 57.2% were female. Median follow-up was 14.3 years (interquartile range: 12.5-16.1). Overall prevalence of sarcopenia was 35.4% in women and 75.5% in men, which increased with age. Prevalence of obesity was 60.8% in women and 54.4% in men. Sarcopenic obesity prevalence was 18.1% in women and 42.9% in men. There were 2782 (61.7%) deaths, of which 39.0% were cardiovascular. Women with sarcopenia and sarcopenic obesity had a higher mortality risk than those without sarcopenia or obesity after adjustment (model 2, hazard ratio (HR): 1.35 (1.05-1.74) and 1.29 (1.03-1.60)). After adjusting for mobility limitations (model 3), sarcopenia alone (HR: 1.32 ((1.04-1.69) but not sarcopenia with obesity (HR: 1.25 (0.99-1.58)) was associated with mortality. For men, the risk of death with sarcopenia and sarcopenic obesity was nonsignificant in both model-2 (HR: 0.98 (0.77-1.25), and HR: 0.99 (0.79-1.23)) and model 3 (HR: 0.98 (0.77-1.24) and HR: 0.98 (0.79-1.22)).

CONCLUSIONS: Older women with sarcopenia have an increased all-cause mortality risk independent of obesity.