Power, Strength, And Physical Function: A Prospective Study Examining All-cause Mortality

Abstract

Functional capacity has traditionally been the primary fitness characteristic studied when examining mortality. With the advent of a variety of muscle strengthening protocols becoming more popular since the turn of the century, the potential role of muscular strength and physical function is now being examined in respect to mortality. PURPOSE: Examine the associations between lower extremity muscular power, muscular strength, physical function and all-cause mortality in a nationally representative sample over U.S adults. METHODS: The study sample (2,631) included participants (≥50 years of age) from the 1999-2002 National Health and Nutrition Examination Survey. The primary independent variables in this study included: time to peak force in seconds (TPFs); peak force in newtons (strength)(PF-N); time to complete a 20-foot walk in seconds(TTCWs). Weighted quartiles (Q) of TPFs, PF-N, and TTCWs were created. The primary dependent variable in this study was all-cause mortality. Cox-proportional hazard models were used for all analyses, adjusting for age, gender, race-ethnicity, education, self-reported smoking, cardiovascular disease, stroke, chronic obstructive pulmonary disease, hypertension, self-reported diabetes, and waist circumference. Quartile 1 (Q1) served as the referent group for analysis with PF-N. Quartile 4 (Q4) served as the reference groups for analyses with TPFs and TTCWs. RESULTS: A dose-response relationship was found for quartiles of increasing PF-N ([Q2: 0.59, 95% CI 0.52-0.68], [Q3: HR 0.48, 95% CI 0.37-0.60], and [Q4: HR 0.32, 95% CI 0.23-0.46]) and decreasing TTCWs ([Q3: HR 0.64, 95% CI 0.53-0.76]), [Q2: HR 0.58, 95% CI 0.46-0.74], [Q1: 0.35, 95% CI 0.26-0.47]). No significant associations were found for TPFs. CONCLUSIONS:Greater PF-N and lower TTCWs time were associated with significantly lower risk for all-cause mortality. Future research should examine the role of upper and lower extremity muscular strength and physical function in predicting all-cause and disease specific mortality.