ObjectivesRecently, the Tokyo Metropolitan Assembly passed an ordinance prohibiting smoking in private homes and cars if children are present. However, no previous study has investigated existing, voluntary home and car smoke-free rules in Japan. Therefore, we examined prevalence and determinants of comprehensive home and car smoke-free rules.DesignA cross-sectional study.SettingInternet survey data with adjustments using inverse probability weighting for ‘being a respondent in an internet survey’.Participants5600 respondents aged 15–69 years in 2015 were analysed to estimate weighted percentages and prevalence ratios (PRs) with 95% CIs of having comprehensive home and car smoke-free rules.Main outcome measuresRespondents who answered ‘smoking is never allowed’ in their home and car were defined as having home and car smoke-free rules.ResultsOverall, 47.0% (95% CI=45.8% to 48.3%) of respondents implemented comprehensive home and car smoke-free rules. People who agreed with ‘smoking relieves stress’ were less likely to have comprehensive smoke-free rules (PR=0.76, 0.71 to 0.82), especially among ever-users of electronic nicotine delivery systems (PR=0.49, 0.30 to 0.81). Higher education was significantly associated with higher PR for comprehensive smoke-free rules (PR=1.30, 1.19 to 1.41). Living with children was significantly associated with higher PR for smoke-free rules among current smokers than not living with children (PR=2.91, 1.99 to 4.27).ConclusionsIn Japan, about 50% of respondents had voluntary smoke-free rules in the home and car. Information on current voluntary smoke-free rules will be useful as baseline information on home and car smoke-free status before enforcement of the 2018 Tokyo home and car smoke-free legislation.
