Hypertension modifies the associations of body mass index and waist circumference with all-cause mortality among older Chinese: a retrospective cohort study

Background The effect of baseline hypertension status on the BMI-mortality association is still unclear. We aimed to explore the relationships of body mass index (BMI) and waist circumference (WC) with all-cause mortality among older hypertensive and normotensive Chinese individuals. Methods This retrospective cohort study was conducted in Xinzheng, Henan Province, Central China. The data came from the residents' electronic health records of the Xinzheng Hospital Information System. A total of 77,295 participants (41,357 hypertensive participants and 35,938 normotensive participants) aged >= 60 years were included from January 2011 to November 2019. Cox proportional hazard regression model was used to examine the relationships. Results During a mean follow-up of 5.3 years, 10,755 deaths were identified (6,377 in hypertensive participants and 4,378 in normotensive participants). In adjusted models, compared with a BMI of 18.5-24 kg/m(2), the hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) of BMI < 18.5, 24-28 and >= 28 kg/m(2) for mortality in hypertensive participants were 1.074 (0.927-1.244), 0.881 (0.834-0.931) and 0.856 (0.790-0.929), respectively, and 1.444 (1.267-1.646), 0.884 (0.822-0.949) and 0.912 (0.792-1.051), respectively, in normotensive participants. Compared with normal waist circumference, the adjusted HRs and 95% CIs of central obesity for mortality were 0.880 (0.832-0.931) in hypertensive participants and 0.918 (0.846-0.996) in normotensive participants. A sensitivity analysis showed similar associations for both hypertensive and normotensive participants. Conclusion Low BMI and WC were associated with a higher risk of all-cause mortality regardless of hypertension status in older Chinese individuals. The lowest risk of death associated with BMI was in the overweight group in normotensive participants and in the obesity group in hypertensive participants.