The interaction between general or abdominal obesity and hypertension on the risk of type 2 diabetes mellitus: a cross-sectional analysis in Iranian adults from the RaNCD cohort study

Interactions between risk factors may influence disease severity. Knowing this relationship is important for preventive interventions and disease control. The purpose of this study was to determine the interactions effects of obesity and hypertension on the risk of type 2 diabetes mellitus (T2DM). The data of 9,283 adults 35 to 65 years were examined from the cohort study of Ravansar Non-Communicable Disease (RaNCD). Waist circumference (WC) was used to identify both general and abdominal obesity based on body mass index (BMI). To assess the interaction between hypertension and obesity (general/abdominal) and the risk of T2DM, the additive interaction was calculated. The adjusted odds ratios for T2DM were 2.38 (1.67, 3.41) in men and 4.02 (2.47, 6.47) in women for the combinations of hypertension and abdominal obesity. The adjusted odds ratios for T2DM were 2.53 (1.63, 3.82) in men and 2.66 (1.92, 3.70) in women for the combinations of hypertension and general obesity. The results of the additive interaction indicators were inconsistent with gender. The relative excess risk due to interaction (interaction between hypertension and central obesity) (RERI), attributable proportion due to interaction (AP) and synergy index (SI) were0.27 (-1.01, 1.54), 0.11 (-0.41, 0.63) and 1.23 (0.41, 3.68) in male and were 0.61 (-1.12, 2.33), 0.23 (0.08, 0.37) and 1.26 (0.60, 2.61) in female, respectively. General/abdominal obesity and hypertension have a synergistic effect on the risk of T2DM. The recommendation for preventing T2DM is lifestyle modification. Large longitudinal studies are necessary to investigate causal relationships.