Abstract MP34: Associations Muscle Quality, Muscle Strength, and Muscle Mass With All-Cause Mortality in Elderly Men and Women

Abstract

Although muscle mass, muscle strength, and muscle quality are important risk factors for disability and mortality in elderly men and women, the associations of these variables with all-cause mortality remain less explored. PURPOSE: We investigated the associations of muscle quality, muscle strength, and muscle mass with all-cause mortality in elderly US men and women. We also compared the strength of these associations with all-cause mortality. Methods: Cox proportional hazards regression was used to examine the associations of muscle quality, muscle strength, and muscle mass with all-cause mortality. We followed 1,361 men and women, aged 60 to 85 years, who participated in the National Health and Nutrition Examination Survey 1999-2002. All participants completed baseline lifestyle factors, and muscle strength and muscle mass measurements. Body composition was estimated by Dual-energy X-ray absorptiometry. Appendicular skeletal muscle mass (SMS) was computed by combining lean tissues in both arms and legs, and relative muscle mass was computed as SMS divided by height in meters squared (AMS). Leg muscle strength (MST) was estimated using the Kin Com MP dynamometer. Leg muscle quality (MQI) was computed as the peak force (Newton) divided by lean mass in the right leg. We further categorized AMS, MST, and MQI as sex-specific quartile categories. The significance of AMS, MST, and MQI with all-cause mortality was also tested by the Cox hazards models with the likelihood ratio statistics with and without adjustment for multiple risk factors. Results: During an average of 9.8 years of follow-up (9,4687 person-years), there were a total of 372 all-cause deaths (85 CVD, 202 chronic diseases). After adjustment for multiple risk factors, the risks of all-cause mortality across MQI quartile categories were (95% CI) 1.00 (Q1, referent), 0.72 (0.55, 0.95), 0.66 (0.49, 0.90), and 0.50 (0.31, 0.80) (P for trend <0.001). The risks of all-cause mortality across MST categories were (95% CI) 1.00 (Q1, referent), 0.85 (0.59, 1.21), 0.50 (0.33, 0.75), and 0.46 (0.31, 0.67) (P for trend <0.001). The risks of all-cause mortality across AMS categories were (95% CI) 1.00 (Q1, referent), 0.77 (0.56, 1.07), 0.75 (0.52, 1.10), and 0.65 (0.47, 0.90) (P for trend = 0.01). As a single measure, after adjustment for multiple risk factors, the hazards for all-cause mortality across MQI, MST, and AMS were 0.97 (p<0.001), 0.99 (p<0.001), and 0.84 (p = 0.001), respectively. When we included all these variables in the fully-adjusted model, only MQI (p = 0.03) was a strong risk factor for all-cause mortality, but not for MST (p = 0.84) and AMS (p = 0.05). Conclusion: Muscle quality was a strong risk factor for all-cause mortality in elderly men and women when compared with muscle strength or relative muscle mass. The American Heart Association should emphasize the importance of improving muscle quality in this geriatric population.