Association between environmental tobacco smoke exposure and risk of type 2 diabetes mellitus in Chinese female never smokers: A population‐based cohort study

Background: Evidence for the association between environmental tobacco smoke (ETS) exposure and the risk of type 2 diabetes mellitus (T2DM) is limited. The aim of this study was to investigate this association in female never smokers. Methods: We analyzed 28 177 female participants of the China Kadoorie Biobank (CKB) in the Suzhou area, who were never smokers and had no diabetes. ETS exposure was defined as being exposed to other people's tobacco smoke either at home, workplace, or in public places at least 1 d/wk. Cox proportional hazard regression models were used to assess the association between ETS exposure and incident T2DM according to the frequency and duration of ETS exposure. Results: A total of 774 incident cases of T2DM were identified during a median 7.3‐year follow‐up. Compared with no ETS exposure, hazard ratios (95% CIs) for all ETS exposure, daily, and ≥14 h/wk ETS exposure were 1.17 (1.00‐1.37), 1.23 (1.04‐1.46), and 1.25 (1.03‐1.53), respectively. Moreover, a positive dose‐response relationship was observed between ETS exposure level and T2DM (all P Conclusions: This prospective study suggests that ETS exposure increases the risk of T2DM incidence with dose‐response relationship in female never smokers. Thus, reducing ETS exposure may help decrease the burden of T2DM in Chinese females.