The association between physical activity and risk of mortality is modulated by grip strength and cardiorespiratory fitness: evidence from 498 135 UK-Biobank participants

Abstract

Aims: It is unclear whether the potential benefits of physical activity differ according to level of cardiorespiratory fitness (CRF) or strength. The aim of this study was to determine whether the association between physical activity and mortality is moderated by CRF and grip strength sufficiently to inform health promotion strategies.

Methods and results: 498 135 participants (54.7% women) from the UK Biobank were included (CRF data available in 67 702 participants). Exposure variables were grip strength, CRF, and physical activity. All-cause mortality and cardiovascular disease (CVD) events were the outcomes. 8591 died over median 4.9 years [IQR 4.3–5.5] follow-up. There was a significant interaction between total physical activity and grip strength (P < 0.0001) whereby the higher hazard of mortality associated with lower physical activity was greatest among participants in the lowest tertile for grip strength (hazard ratio, HR:1.11 [95% CI 1.09–1.14]) and lowest among those in the highest grip strength tertile (HR:1.04 [1.01–1.08]). The interaction with CRF did not reach statistical significance but the pattern was similar. The association between physical activity and mortality was larger among those in the lowest tertile of CRF (HR:1.13 [1.02–1.26]) than those in the highest (HR:1.03 [0.91–1.16]). The pattern for CVD events was similar.

Conclusions: These data provide novel evidence that strength, and possibly CRF, moderate the association between physical activity and mortality. The association between physical activity and mortality is strongest in those with the lowest strength (which is easily measured), and the lowest CRF, suggesting that these sub-groups could benefit most from interventions to increase physical activity.

Figure 1

Association between all-cause mortality and physical activity within cardiorespiratory fitness (A) and grip strength (B) strata. Data presented as hazard ratio (95% CI), adjusted for age, sex, ethnicity, deprivation index, BMI, smoking status, total sedentary time, alcohol intake, depression, diabetes, hypertension, cancer diagnosis, stroke, angina, heart attack, and long-standing illness. Q5 represents highly active individuals and Q1 highly inactive individuals. Individuals in the highest quintile of physical activity (Q5) and the highest tertile for cardiorespiratory fitness or grip strength were used as the reference group (*). P-interaction describes the interaction between physical activity and cardiorespiratory fitness or grip strength with all-cause mortality; P-trend describes the association between physical activity with all-cause mortality within tertiles for cardiorespiratory fitness or grip strength.

Figure 2

Association between cardiovascular disease events and physical activity within cardiorespiratory fitness (A) and grip strength (B) strata. Data presented as hazard ratio (95% CI), adjusted for age, sex, ethnicity, deprivation index, BMI, smoking status, total sedentary time, alcohol intake, depression, diabetes, hypertension, cancer diagnosis, stroke, angina, heart attack, and long-standing illness. Q5 represents highly active individuals and Q1 highly inactive individuals. Individuals in the highest quintile of physical activity (Q5) and the highest tertile for cardiorespiratory fitness or grip strength were used as the reference group (*). P-interaction describes the interaction between physical activity and cardiorespiratory fitness or grip strength with CVD events; P-trend describes the association between physical activity with CVD events within tertiles for cardiorespiratory fitness or grip strength.