Association between exposure to secondhand smoking at home and tooth loss in Japan: A cross-sectional analysis of data from the 2016 National Health and Nutrition Survey

INTRODUCTION Tooth loss affects oral health and physical and social functions. With widespread population aging, its prevalence is increasing. Secondhand smoking is a risk factor for oral diseases; however, in Japan, there are currently no regulations restricting exposure to secondhand smoke at home. This cross-sectional study examined the association between secondhand smoking at home and tooth loss among Japanese adults. METHODS The study examined secondary data from the 2016 National Health and Nutrition Survey, Japan. The self-reported responses of 18812 non-smokers aged >= 20 years were analyzed. The association between exposure to secondhand smoke at home and number of teeth was examined through multiple linear regression with multiple imputation. To obtain a more normal distribution, logarithmic transformation was applied to the number of teeth that deviated substantially from a normal distribution. Adjustments were made for sex, age, occupation, household size, dental check-up within the past year, and exposure to secondhand smoke outside the home. RESULTS Overall, 8.4% of the respondents were exposed to secondhand smoking at home almost every day; this percentage was larger among younger respondents, who also had more teeth than the older respondents. Although the univariate linear regression did not show a positive association between exposure to secondhand smoke and tooth loss, the multivariate-adjusted analysis revealed that respondents who were exposed to secondhand smoke at home almost every day had fewer teeth (beta=-0.04; 95% CI:-0.07 --0.01). CONCLUSIONS The present results suggest that exposure to secondhand smoke at home increases the risk of tooth loss.