Associations of education and income with hazardous drinking among postpartum women in Japan: results from the TMM BirThree Cohort Study

Background: Although the postpartum period is suggested to provide an ideal opportunity for interventions to prevent hazardous drinking, evidence on the associations of education and income with hazardous drinking during this period is limited, including in Japan. Methods: We analyzed data from 11,031 women who participated in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study in Japan. Hazardous drinking was defined as ethanol intake of ≥20 g/day 1 year after delivery. We conducted multiple logistic regression analyses to examine whether educational attainment or equivalent household income was associated with hazardous drinking, adjusting for age, parity, drinking status during pregnancy, work status, postpartum depression, breastfeeding, and income/education. We also conducted stratified analyses by income and education groups. Results: The prevalence of hazardous drinking 1 year after delivery was 3.6%. Lower education was associated with hazardous drinking; the odds ratio (95% confidence interval) of high school education or lower compared with university education or higher was 2.17 (1.59–2.98). Lower income was also associated with hazardous drinking, but this association disappeared after further adjustments for education; the odds ratios (95% confidence intervals) of the lowest compared with highest level of income were 1.42 (1.04–1.94) and 1.12 (0.81–1.54), respectively. A significant interaction was detected; lower education and lower income were associated with increased risks of hazardous drinking only in a lower income group and lower education group, respectively. Conclusions: Postpartum women with lower education and lower income had higher risks of hazardous drinking in Japan.