Husbands' smoking and risk of diabetes in reproductive-aged Chinese women: a nationwide population-based cohort study.

backgroundPreventing impaired fasting glucose (IFG) and diabetes mellitus (DM) among reproductive-age women is important for both maternal and infant health. Although secondhand smoke exposure increases DM risk, evidence on glycemic impact from a single predominant household source remains limited. In populations with marked sex disparities in smoking prevalence, spousal smoking often constitutes women's primary exposure source. We examined temporal associations between husbands' smoking patterns with incident IFG and DM among reproductive-age Chinese women.

methodsThis prospective cohort analyzed 2,828,544 couples from China's National Free Preconception Checkup Project (2010-2020) with two preconception examinations (median interval: 2.12 years). We included non-smoking women aged 20-49 years without pre-diagnosed DM and fasting plasma glucose (FPG) <7.0 mmol/L at baseline. Husbands' smoking was categorized as consistently non-smoking, consistently smoking, ex-smoking, or newly smoking. For consistently smoking husbands, we assessed smoking intensity (cigarettes per day) and cumulative exposure (pack-years). Among 2,475,950 women with baseline normal glycemia, we examined incident IFG (FPG 5.6-6.9 mmol/L) and DM (FPG ≥7.0 mmol/L or self-reported). Among 352,594 women with baseline IFG, we examined glycemic progression to DM.

resultsOf women with baseline normal glycemia, 10.1% developed IFG and 1.0% developed DM. Among husbands, 62.7% were consistently non-smoking, 16.2% consistently smoking, 11.5% ex-smoking, and 9.6% newly smoking. Compared to women with consistently non-smoking husbands, those with consistently smoking (adjusted odds ratio (AOR) 1.07, 95% confidence interval (CI) 1.03-1.11), ex-smoking (AOR 1.12, 95% CI 1.08-1.17), and newly smoking husbands (AOR 1.17, 95% CI 1.12-1.22) had higher odds of DM. Dose-response relationships were observed for cumulative pack-years with both IFG and DM (both P trend<0.05). Among women with baseline IFG, husbands' smoking cessation was associated with lower odds of DM progression (AOR 0.91, 95% CI 0.84-0.99) compared with continued smoking.

conclusionsHusbands' smoking increased wives' IFG and DM risks with dose-response relationships for cumulative exposure. Among women with baseline IFG, spousal smoking cessation was associated with reduced odds of DM progression. Preconception examination is a critical teachable moment for family-based smoking cessation interventions to prevent dysglycemia. These findings support expanding smoke-free policies to private settings and implementing comprehensive household tobacco control strategies.