Legislative smoking bans for reducing secondhand smoke exposure, smoking prevalence and tobacco consumption.

BACKGROUND: Smoking bans have been implemented in a variety of settings, as well as being part of policy in many jurisdictions to protect the public and employees from the harmful effects of secondhand smoke (SHS). They also offer the potential to influence social norms and smoking behaviour of those populations they affect. OBJECTIVES: To assess the extent to which legislation-based smoking bans or restrictions reduce exposure to SHS, help people who smoke to reduce tobacco consumption or lower smoking prevalence and affect the health of those in areas which have a ban or restriction in place. SEARCH STRATEGY: We searched the Cochrane Tobacco Addiction Group Specialised Register, MEDLINE, EMBASE, PsycINFO, CINAHL, Conference Paper Index, and reference lists and bibliographies of included studies. We also checked websites of various organisations. Date of most recent search; July 1st 2009. SELECTION CRITERIA: We considered studies that reported legislative smoking bans and restrictions affecting populations. The minimum standard was having a ban explicitly in the study and a minimum of six months follow-up for measures of smoking behaviour. We included randomized controlled trials, quasi-experimental studies (i.e. non-randomized controlled studies), controlled before and after studies, interrupted-time series as defined by the Cochrane Effective Practice and Organization of Care Group, and uncontrolled pre- and post-ban data. DATA COLLECTION AND ANALYSIS: Characteristics and content of the interventions, participants, outcomes and methods of the included studies were extracted by one author and checked by a second. Because of heterogeneity in the design and content of the studies, we did not attempt a meta-analysis. We evaluated the studies using qualitative narrative synthesis. MAIN RESULTS: There were 50 studies included in this review. Thirty-one studies reported exposure to secondhand smoke (SHS) with 19 studies measuring it using biomarkers. There was consistent evidence that smoking bans reduced exposure to SHS in workplaces, restaurants, pubs and in public places. There was a greater reduction in exposure to SHS in hospitality workers compared to the general population. We failed to detect any difference in self-reported exposure to SHS in cars. There was no change in either the prevalence or duration of reported exposure to SHS in the home as a result of implementing legislative bans. Twenty-three studies reported measures of active smoking, often as a co-variable rather than an end-point in itself, with no consistent evidence of a reduction in smoking prevalence attributable to the ban. Total tobacco consumption was reduced in studies where prevalence declined. Twenty-five studies reported health indicators as an outcome. Self-reported respiratory and sensory symptoms were measured in 12 studies, with lung function measured in five of them. There was consistent evidence of a reduction in hospital admissions for cardiac events as well as an improvement in some health indicators after the ban. AUTHORS' CONCLUSIONS: Introduction of a legislative smoking ban does lead to a reduction in exposure to passive smoking. Hospitality workers experienced a greater reduction in exposure to SHS after implementing the ban compared to the general population. There is limited evidence about the impact on active smoking but the trend is downwards. There is some evidence of an improvement in health outcomes. The strongest evidence is the reduction seen in admissions for acute coronary syndrome. There is an increase in support for and compliance with smoking bans after the legislation.