Additive interaction of conjoint tobacco smoking and heavy drinking on hypertension prevalence in rural Uganda: a community-based cross-sectional study.

Background: The prevalence of hypertension is high in Uganda, which places a significant burden on an already strained healthcare system. The behavioural risk factors, such as unhealthy diet, tobacco use, physical inactivity, and heavy drinking, contribute to hypertension development and complications. This study explored the associations of combined tobacco smoking and heavy alcohol consumption with existing hypertension in a community-based cross-sectional study conducted in two rural districts of Uganda.

Methods: We analysed data collected between December 2018 and January 2019 from 4,372 adults aged 25-70 from 3,689 random households in the Mukono and Buikwe districts, Uganda. Using logistic regression, crude, and adjusted odds ratios were calculated to describe the associations between participant characteristics, smoking, drinking behaviours, and high blood pressure (HBP). To determine effect modification due to combined tobacco smoking and heavy drinking, the relative excess risk due to interaction (RERI) was computed. All analyses were performed via R programming software version 4.2.3.

Results: HBP was prevalent in 23% of the participants. Smokers were 1.36 times more likely to have HBP than non-smokers (Crude OR, 1.36; 95% CI, 1.04-1.76). Compared with non-drinkers, moderate alcohol drinkers were 1.45 times more likely to have HBP (AOR, 1.45; 95% CI, 1.18-1.79), and heavy drinkers were 2.53 times more likely to have HBP (AOR, 2.53; 95% CI, 1.92-3.32). The RERI indicated an additive interaction effect between smoking and heavy drinking, with conjoint smokers and heavy drinkers having 45% higher odds of having HBP than the summation of the individual risk due to smoking and heavy drinking.

Conclusion: Tobacco smoke interacts with heavy alcohol consumption to increase the risk of increased blood pressure (BP) when it cooccurs. Integrated intervention strategies targeting both smoking and heavy drinking are essential for reducing the incidence of hypertension in rural Uganda.