Dose-dependent association between muscle-strengthening activities and all-cause mortality: Prospective cohort study among a national sample of adults in the USA

Background. - We have a limited understanding of the association between behavioural participation in muscle-strengthening activities (MSA) and all-cause mortality. Aim. - To determine the effect of MSA on all-cause mortality, and examine a potential dose response relationship between the frequency with which MSA are performed and the incidence of all-cause mortality. Methods. - Individuals (8772 adults aged >= 20 years) from the 2003-2006 National Health and Nutritional Examination Survey were evaluated for baseline characteristics, then followed for an average of 6.7 years. MSA were assessed at baseline as the number of self-reported sessions completed within the past 30 days. Analyses were performed in 2015. Results. - Only 18.6% of individuals met MSA guidelines (2-3 MSA sessions/week) at baseline, while those performing any form of MSA had a 23% reduced risk of all-cause mortality (hazard ratio [HR]: 0.77; 95% confidence interval: 0.60-0.98; P=0.04). Additionally, we created a five category variable to determine whether a dose-response relationship existed between MSA and premature mortality; only individuals performing 8-14 sessions over a 30-day period (current MSA guidelines) had a reduced risk of all-cause mortality (FIR: 0.70; P= 0.02). Results were similar for CVD-specific mortality. Conclusion. - The national recommendations that 2-3 MSA sessions be performed per week appear to be most effective at reducing the risk of premature all-cause mortality; however, despite these recommendations, the majority of the adult population in the USA still fails to perform any MSA. Future studies should determine strategies for increasing adherence to these established guidelines. (C) 2016 Elsevier Masson SAS. All rights reserved.