Determinants and consequences of smoke-free homes: findings from the International Tobacco Control (ITC) Four Country Survey.

OBJECTIVE To report on prevalence, trends and determinants of smoke-free home policies in smokers' homes in different countries and to estimate the effects of these policies on smoking cessation. DESIGN Two waves of the International Tobacco Control (ITC) Four Country Survey (ITC-4), a cohort survey of smokers conducted by telephone. Wave 1 was conducted in October/December 2002 with broadly representative samples of over 2000 adult (>or= 18 years) cigarette smokers in each of the following four countries: Canada, the United States, the United Kingdom, and Australia, 75% of whom were followed up at Wave 2 on average seven months later. KEY MEASURES Levels of smoking restrictions in homes (both waves). RESULTS Australian smokers were most likely to live in smoke-free homes and UK smokers least likely (34% v 15% at Wave 1). Levels of smoke-free homes increased between waves. Logistic regressions indicated that the main independent predictors of smokers reporting smoke-free homes or implementation of a smoke-free policy between waves included household factors such as having a child, particularly a young child, and having other non-smoking adults in the household. Positive attitudes to smoke-free public places and/or reported presence of smoke-free public places were independent predictors of having or implementing smoke-free homes, supporting a social diffusion model for smoking restrictions. Intentions to quit at Wave 1 and quitting activity between survey waves were associated with implementing bans between Waves 1 and 2. Presence of bans at Wave 1 was associated with significantly greater proportions of quit attempts, and success among those who tried at Wave 2. There was no significant interaction between the predictive models and country. CONCLUSIONS Smoke-free public places seem to stimulate adoption of smoke-free homes, a strategy associated with both increased frequency of quit attempts, and of the success of those attempts.