The effects of interactions between smoking and abdominal obesity on prediabetes mellitus

Abstract Background: Few studies have investigated the interaction effect of smoking and abdominal obesity on the risk of prediabetes mellitus (PDM) among rural adults in Southwest China. The primary purpose of the current study was to investigate the potential interactive effects of smoking and abdominal obesity on the development of PDM. Methods: The data were obtained from a cross-sectional survey conducted by a two-stage random sampling method around Rongchang District in ChongQing municipality, Southwest China, in 2022. In total, 3,017 participants aged 40 to 79 years were included in the study. Multivariate logistic regression analyses were performed to evaluate the associated risk factors for PDM, and the effects of multiplicative and additive interactions between smoking and abdominal obesity were also assessed by indicators including the relative excess risk due to interaction (RERI), the attributable proportion due to interaction (AP) and the synergy index (SI). Results: A total of 3,017 individuals, with an average age of 62.14±11.13 years, participated in the present study, and the prevalence of PDM among the participants was 38.98%. After adjustments for confounding variables, current smoking status (OR=1.257, 95% CI: 1.041-1.518) and abdominal obesity (OR=1.403, 95% CI: 1.184-1.662) were significantly linked to an elevated risk of PDM. The multiplicative interaction analyses demonstrated that current smoking status was positively associated with PDM (OR=1.317, 95% CI: 1.013-1.711), while a similar association was not observed between abdominal obesity and PDM (OR=1.148, 95% CI: 0.943-1.396). A significant additive interaction was observed between current smoking and abdominal obesity in terms of PDM risk (OR=3.559, 95% CI: 2.544-4.978). RERI = 2.094 (0.952-3.236), indicating a coexisting risk attributable to additive interaction; AP = 0.589 (0.432-0.745), indicating that 58.90% of all PDM individuals exposed to both risk factors could be attributed to the synergistic effect of current smoking and abdominal obesity; SI = 5.509 (2.152-14.104), suggesting that the synergistic risk between current smoking and abdominal obesity was 5.509 times greater than the sum of effects observed in individuals exposed to a single factor alone. Conclusion: The prevalence of PDM was 38.98% among individuals aged 40-79 years in Rongchang, potentially indicating a greater future incidence of diabetes mellitus. Notably, smoking and abdominal obesity exhibit a positive synergistic effect on the risk of PDM.