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 more common among those from households with smokers.•Being from smoking households is linked to low educational levels in young adulthood.•More childhood household smokers corresponds to worse outcomes for young adults.•Exposure to household smokers in childhood appears to perpetuate health inequality. 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 (P