Effect of Family Medical History of Hypertension and Its Interaction with Diabetes on an Additive Scale on the Diagnosis of Hypertension Among Middle-Aged and Older Adults in India: Longitudinal Ageing Study in India

Introduction: Among individuals diagnosed with type 2 diabetes, the family medical history remains an independent risk factor for elevated blood pressure. In fact, the individual effect of diabetes on the risk of hypertension could not truly reflect the actual effect of exposures, and there might be an interaction with a family history of hypertension. The coexistence of these two factors may synergistically increase the risk of hypertension, leading to adverse health outcomes. This study aimed to examine the effect of the additive interaction between a family medical history of hypertension and diabetes on the diagnosis of hypertension among individuals aged 45 years and older in India. Methods: The study used data from the Longitudinal Ageing Study in India (LASI) Wave 1 (2017–2018), comprising a total sample size of 58,667 individuals aged 45 years and above. An additive model was employed to estimate the interaction effect of the family medical history of hypertension with diabetes on the diagnosis of hypertension by calculating three measures of additive interaction: the relative excess risk due to interaction (RERI), attribution proportion (AP), and synergy index (S). Results: Individuals with a history of both the parents and siblings had an AOR (adjusted odds ratio) of 2.1 and 3.3 for hypertension. In the adjusted model, the RERI, AP, and S for hypertension were 3.09 (95% CI: 1.28–4.89), 37.0% (0.37; 95% CI: 0.22–0.52), and 1.73 (95% CI: 1.31–2.27), respectively, which indicates that there is a significant positive interaction effect between a family history of hypertension and diabetes on the diagnosis of hypertension. Conclusions: The study findings strongly indicate that a family medical history of hypertension and diabetes has a significant and positive interaction effect on the risk of hypertension. Therefore, it is imperative to consider both the family history and diabetes in hypertension risk assessments and develop targeted primary and secondary prevention strategies for specific vulnerable subpopulations.