Association of household smoking status in childhood with young adults' educational attainment and smoking status: Results from a series of population-based cross-sectional surveys in Japan.

Smoking in young adulthood is a risk factor for future health-related disabilities and a cause of expanding health inequalities. Education and smoking are inversely associated. Using population-based representative data, this study aimed to clarify how the presence of household smokers during childhood related to both current smoking status and educational attainment among young adults. Surveys were distributed to young adults (19-20 years) invited to coming-of-age ceremonies in 2014-2017 in a rural area in Japan. Data were collected on low educational attainment (defined as ≤ 12 years of education), current smoking status, and childhood household smoking status. We used logistic regression models to calculate odds ratios (ORs) of low educational attainment for household smoking status. A total of 17.6% of men (n = 1077) and 3.8% of women (n = 1021) were current smokers. Current smoking was more common among participants from households with smokers ( < 0.001 for both men and women). The odds of low educational attainment were significantly higher for participants from smoking households (OR: 1.59, 95% confidence interval [CI]: 1.17-2.17 for men; OR: 2.29, 95% CI: 1.61-3.24, for women). All associations were characterized by a dose-response relationship with the number of household smokers. The number of household smokers in childhood was positively associated with current smoking and negatively associated with level of educational attainment among young adults. Controlling for year and geographical area, exposure to family smokers in childhood appears to be a risk factor for the intergenerational transmission of health inequalities.