Synergistic harmful interaction between sustained physical inactivity and hypertension/diabetes mellitus on the risk of all-cause mortality: a retrospective observational cohort study

OBJECTIVE Hypertension, diabetes mellitus and physical inactivity can cause cardiovascular complications or premature death. However, it has not been clarified whether those major comorbidities and physical activity interact in affecting health outcomes. The aim of this study is to evaluate the potential interaction between temporal physical activity profiles and hypertension or diabetes mellitus on the risk for all-cause mortality. METHODS This study used Korea National Health Insurance Service (KNHIS) database and included about 6.5 million participants who underwent health screening in 2009 and 2011. Physical activity was evaluated as 2-year change based on self-reported survey using 7-day recall method, and grouped as remained active, inactive-to-active, active-to-inactive, or remained inactive. Participants were categorized into groups according to the presence of hypertension/diabetes mellitus. Outcome included all-cause mortality. RESULTS In total, 6 554 082 participants (48.4 ± 13.3 years; 56.7% men) were included. During a median 6.4-year follow-up, 83 241 deaths occurred. Compared with the 'remained active' group, other groups had a higher mortality risk after adjustment for covariates [adjusted hazard ratio (aHR) 1.17, 95% CI 1.13-1.21 in the 'inactive-to-active' group, aHR 1.28, 95% CI 1.24-1.32 in the 'active-to-inactive' group, aHR 1.52, 95% CI 1.48-1.57 in the 'remained inactive' group). Hypertension and diabetes mellitus were significant effect modifiers in the association between physical activity and the risk of all-cause mortality (P for interaction