March 16, 2016
Yes, it is true we are all aging, some faster than others, but inevitably all of us to the same conclusion. Perhaps the greatest predictor of how we are aging is our fitness.1-2 Specifically, our cardiovascular and muscular system fitness are the best predictors. Can we measure our muscular fitness and through that measure can we predict our future mortality? The answer appears to be yes.
The Prospective Urban-Rural Epidemiology (PURE) Study is a large, longitudinal population study conducted across 17 countries with different levels of industrialization.3 Participants aged 35-70 years were assessed for grip strength using a dynamometer and then followed for 4 years for all-cause mortality, cardiovascular mortality, non-cardiovascular mortality, myocardial infarction, stroke, diabetes, cancer, pneumonia, hospital admission for pneumonia or chronic obstructive pulmonary disease (COPD) , injury due to fall, and fracture. There were a total of almost 140,000 participants. Grip strength was inversely associated with all-cause mortality hazard ratio (HR) per 5 kg reduction in grip strength of 1.16 (95% CI: 1.13-1.20, P<0.0001), non-cardiovascular mortality had an HR of 1.17 (95% CI: 1.12-1.21, P<0.0001), myocardial infarction had an HR of 1.07 (95% CI: 1.02-1.11, P=0.02), and stroke had an HR of 1.09 (95% CI: 1.05-1.15, p<0.0001). Grip strength was actually a stronger predictor that SBP! There was no significant association between grip strength with diabetes, risk of hospital admission for pneumonia or COPD, injury from fall or fracture. Interestingly, this applied only to high-income countries (i.e., Malaysia, Turkey, Brazil, Argentina, Poland, Chile, United Arab Emirates, Canada, and Sweden), but not to middle-income and low-income countries.
What is the application to this study’s findings? First, stay fit! Second, grip strength, a relatively simple and inexpensive biomarker can determine those individuals that are at a higher risk of death as well as morbidity and mortality from cardiovascular disease. Third, the finding that grip strength is a more powerful predictor than SBP raises important questions about incorporating this measure in our clinical assessments immediately. Third, one should not extrapolate these findings to lower limb strength. But they do underline the importance of skeletal muscle function in aging and especially in the health of aging. Lastly, studies now need to be done to determine how best to set up a training program for these individuals with low grip strength to prolong their lives, including ascertaining whether traditional cardiovascular agents can improve grip strength. These findings certainly raise the bar on research on skeletal muscle biology as we age.
Mark A. Munger, PharmD, FCCP, FACC, is a Professor of Pharmacotherapy and Adjunct Professor of Internal Medicine, at the University of Utah, where he also serves as the Associate Dean, Academic Affairs for the College of Pharmacy.
1. Kodama S, Saito K, Tanaka S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA.2009;301(19):2024-2035.
2. Ortega FB, Silventoinen K, Tynelius P, Rasmussen F. Muscular strength in male adolescents and premature death: cohort study of one million participants. BMJ.2012;345:e7279.
3. Leong DP, Teo KK, Rangarajan S, et al.; Prospective Urban Rural Epidemiology (PURE) Study Investigators. Prognostic value of grip strength: Findings from the Prospective Urban Rural Epidemiology (PURE) study. Lancet. 2015;386(9990):266-273.