Associations of Muscle Mass and Strength with All-Cause Mortality among US Older Adults

Abstract

Introduction: Recent studies suggested that muscle mass and muscle strength may independently or synergistically affect aging-related health outcomes in older adults; however, prospective data on mortality in the general population are sparse.

Methods: We aimed to prospectively examine individual and joint associations of low muscle mass and low muscle strength with all-cause mortality in a nationally representative sample. This study included 4449 participants age 50 yr and older from the National Health and Nutrition Examination Survey 1999 to 2002 with public use 2011 linked mortality files. Weighted multivariable logistic regression models were adjusted for age, sex, race, body mass index (BMI), smoking, alcohol use, education, leisure time physical activity, sedentary time, and comorbid diseases.

Results: Overall, the prevalence of low muscle mass was 23.1% defined by appendicular lean mass (ALM) and 17.0% defined by ALM/BMI, and the prevalence of low muscle strength was 19.4%. In the joint analyses, all-cause mortality was significantly higher among individuals with low muscle strength, whether they had low muscle mass (odds ratio [OR], 2.03; 95% confidence interval [CI], 1.27-3.24 for ALM; OR, 2.53; 95% CI, 1.64-3.88 for ALM/BMI) or not (OR, 2.66; 95% CI, 1.53-4.62 for ALM; OR, 2.17; 95% CI, 1.29-3.64 for ALM/BMI). In addition, the significant associations between low muscle strength and all-cause mortality persisted across different levels of metabolic syndrome, sedentary time, and LTPA.

Conclusions: Low muscle strength was independently associated with elevated risk of all-cause mortality, regardless of muscle mass, metabolic syndrome, sedentary time, or LTPA among US older adults, indicating the importance of muscle strength in predicting aging-related health outcomes in older adults.

Figure 1

Prevalence of low muscle mass (LMM) and low muscle strength (LMS) in US adults aged 50 years and older in the NHANES 1999–2002. A. Prevalence of LMM (ALM) and LMS in single and combination by gender; B. Prevalence of LMM (ALM/BMI) and LMS in single and combination by gender; C. Prevalence of LMM (ALM) and LMS in single and combination by race; D. Prevalence of LMM (ALM/BMI) and LMS in single and combination by race.

Figure 2

Associations of low muscle mass (LMM) and low muscle strength (LMS) with all-cause mortality. A. Individual associations of LMM and LMS with all-cause mortality. B and C. Joint associations of LMM and LMS with all-cause mortality in US adults aged 50 years and older in the NHANES 1999–2002. The definitions of LMM were based on ALM (B) and ALM/BMI (C). Relative Risks (RR) of all-cause mortality were estimated from multivariable logistic regression models which were adjusted by age, gender, race, BMI, smoking, alcohol use, education, LTPA, sedentary time, CVD, diabetes, cancer, COPD, and CKD. CI: confidence interval. P for interaction = 0.235 in B, and 0.432 in C.

Figure 3

Joint associations of low muscle mass (LMM) and MetS, or low muscle strength (LMS) and MetS with all-cause mortality. Individual association of MetS with all-cause mortality was shown in A. The definitions of LMM were based on ALM (B) and ALM/BMI (C) in the joint analyses of LMM and MetS; the joint associations of LMS and MetS with all-cause mortality were shown in D. Relative Risks (RR) of all-cause mortality were estimated from multivariable logistic regression models which were adjusted by age, gender, race, BMI, smoking, alcohol use, education, LTPA, sedentary time, CVD, diabetes, cancer, COPD, and CKD. P for interaction = 0.058 in A, 0.212 in B, and 0.317 in C.

Figure 4

Joint associations of low muscle mass (LMM) and sedentary time, or low muscle strength (LMS) and sedentary time with all-cause. Individual association of sedentary time with all-cause mortality was shown in A. The definitions of LMM were based on ALM (B) and ALM/BMI (C) in the joint analyses of LMM and sedentary time; the joint associations of LMS and sedentary time with all-cause mortality were shown in D. Relative Risks (RR) of all-cause mortality were estimated from multivariable logistic regression models which were adjusted by age, gender, race, BMI, smoking, alcohol use, education, LTPA, sedentary time, CVD, diabetes, cancer, COPD, and CKD. P for interaction = 0.651 in A, 0.808 in B, and 0.807 in C.

Figure 5

Joint associations of low muscle mass (LMM) and LTPA, or low muscle strength (LMS) and LTPA with all-cause mortality. Individual associations of LTPA with all-cause mortality were shown in A. The definitions of LMM were based on ALM (B) and ALM/BMI (C) in the joint analyses of LMM and LTPA; the joint associations of LMS and LTPA with all-cause mortality were shown in D. Relative Risks (RR) of all-cause mortality were estimated from multivariable logistic regression models which were adjusted by age, gender, race, BMI, smoking, alcohol use, education, LTPA, sedentary time, CVD, diabetes, cancer, COPD, and CKD. P for interaction = 0.038 in A, 0.152 in B, and 0.187 in C.