Impacts of hypertension and diabetes on the incidence of cardiovascular diseases and all-cause mortality: findings from the China Health and Retirement Longitudinal Study cohort

Objective: The study aimed to examine the individual and joint effects of hypertension and diabetes on cardiovascular diseases and all-cause mortality among the middle-aged and older Chinese population. Methods: A total of 9681 individuals without preexisting CVD from the China Health and Retirement Longitudinal Study (CHARLS) were included. Participants were classified into four different groups: hypertension alone, diabetes alone, both conditions, neither condition. Multivariate Cox proportional hazards models were performed to estimate the risks of all-cause mortality and CVD. Results: During the 7-year follow-up, 967 deaths and 1535 CVD events were documented. Compared to individuals without hypertension and diabetes, hypertension alone [adjusted hazard ratio (aHR) 1.571, 95% confidence interval (CI) 1.316–1.875, P < 0.001], diabetes alone (aHR 1.618, 95% CI 1.187–2.205, P < 0.01) and comorbid hypertension and diabetes (aHR 2.041, 95% CI 1.557–2.677, P < 0.001) increased risks of all-cause mortality. The aHRs for CVD events in individuals with both conditions, hypertension alone and diabetes only were 2.011 (95% CI 1.651–2.449, P < 0.001), 1.408 (95% CI 1.233–1.608, P < 0.001) and 1.036 (95% CI 0.808–1.327, P > 0.05), respectively. The risk of CVD among those with comorbid hypertension and diabetes exceeded the sum of the risks due to hypertension and diabetes alone (relative excess risk ratio = 0.567, 95% CI 0.136–0.999). Conclusion: Individuals with comorbid hypertension and diabetes had greater risks of CVD and all-cause mortality, beyond those associated with either condition alone. The synergistic interaction between hypertension and diabetes aggravated the risk of CVD.