Associations of Education and Income With Secondhand Smoke Exposure Among Non-Smoking Pregnant Women in Japan: The Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study

Abstract

Background: Associations of education and income with secondhand smoke (SHS) exposure have been well documented in the general population. However, evidence among non-smoking pregnant women is limited, including in Japan. The purpose of the study was to examine the associations of education and income with SHS exposure among non-smoking pregnant women in Japan.Methods: We analyzed data from 17815 non-smoking pregnant women in Japan who participated in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study from 2013 to 2017. SHS exposure was defined as indoor exposure to someone else’s cigarette smoke ≥1 day/week during pregnancy. Multiple logistic regression analyses were conducted to examine whether pregnant women’s educational attainment or equivalent household income was associated with SHS exposure, adjusting for age, work status, smoking history, partners’ education, and income/education. Stratified analyses by work status were also conducted.Results: The prevalence of SHS exposure during pregnancy was 34.0%; 29.4% among non-working women and 37.1% among working women. Lower educational attainment was associated with an increased risk of SHS exposure; the odds ratio of high school education or lower compared with university education or higher was 1.78 (95% confidence interval, 1.59–1.99). Lower equivalent household income was associated with an increased risk of SHS exposure; the odds ratio of the lowest compared with the highest level of income was 1.67 (95% confidence interval, 1.51–1.84). These associations did not differ between non-working women and working women.Conclusions: Pregnant women with lower education and/or lower household income had higher risks of SHS exposure in Japan. These findings imply that educational interventions and financial incentives are needed for pregnant women and their household smokers in helping to reduce SHS exposure among non-smoking pregnant women.