http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD005992.pub3/abstract
Abstract
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 the smoking behaviour of those populations they affect. Since the first version of this review in 2010, more countries have introduced national smoking legislation banning indoor smoking.
Objectives
To assess the effects of legislative smoking bans on (1) morbidity and mortality from exposure to secondhand smoke, and (2) smoking prevalence and tobacco consumption.
Search methods
We searched the Cochrane Tobacco Addiction Group Specialised Register, MEDLINE, EMBASE, PsycINFO, CINAHL and reference lists of included studies. We also checked websites of various organisations. Date of most recent search; February 2015.
Selection criteria
We considered studies that reported legislative smoking bans affecting populations. The minimum standard was having an indoor smoking ban explicitly in the study and a minimum of six months follow-up for measures of smoking behaviour. Our search included a broad range of research designs including: 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 Organisation of Care Group, and uncontrolled pre- and post-ban data.
Data collection and analysis
One author extracted characteristics and content of the interventions, participants, outcomes and methods of the included studies and a second author checked the details. We extracted health and smoking behaviour outcomes. We did not attempt a meta-analysis due to the heterogeneity in design and content of the studies included. We evaluated the studies using qualitative narrative synthesis.
Main results
There are 77 studies included in this updated review. We retained 12 studies from the original review and identified 65 new studies. Evidence from 21 countries is provided in this update, an increase of eight countries from the original review. The nature of the intervention precludes randomized controlled trials. Thirty-six studies used an interrupted time series study design, 23 studies use a controlled before-and-after design and 18 studies are before-and-after studies with no control group; six of these studies use a cohort design. Seventy-two studies reported health outcomes, including cardiovascular (44), respiratory (21), and perinatal outcomes (7). Eleven studies reported national mortality rates for smoking-related diseases. A number of the studies report multiple health outcomes. There is consistent evidence of a positive impact of national smoking bans on improving cardiovascular health outcomes, and reducing mortality for associated smoking-related illnesses. Effects on respiratory and perinatal health were less consistent. We found 24 studies evaluating the impact of national smoke-free legislation on smoking behaviour. Evidence of an impact of legislative bans on smoking prevalence and tobacco consumption is inconsistent, with some studies not detecting additional long-term change in existing trends in prevalence.
Authors’ conclusions
Since the first version of this review was published, the current evidence provides more robust support for the previous conclusions that the introduction of a legislative smoking ban does lead to improved health outcomes through reduction in SHS for countries and their populations. The clearest evidence is observed in reduced admissions for acute coronary syndrome. There is evidence of reduced mortality from smoking-related illnesses at a national level. There is inconsistent evidence of an impact on respiratory and perinatal health outcomes, and on smoking prevalence and tobacco consumption.
Plain language summary
Does legislation to ban smoking reduce exposure to secondhand smoke and smoking behaviour?
Since the first national legislation banning indoor smoking in all public places was introduced in 2004, there has been an increase in the number of countries, states and regions adopting similar smoke-free legislation banning smoking in public places and work places since this review was first published. The main reason is to protect nonsmokers from the harmful health effects of exposure to secondhand smoke. Another reason is to provide a supportive environment for people who want to quit smoking.
Study characteristics
We searched for studies that investigated the effect of introducing a ban on any measures of health, or on smoking behaviour (up to February 2015). Since the previous version of this review had shown clear evidence that introducing legislation to ban smoking in public places does reduce exposure to secondhand smoke (SHS) in those places, we did not include studies that only reported exposure to SHS. We included 77 studies from 21 countries in this updated review. Studies of health outcomes typically used data from hospitals to look for changes in rates of admissions, discharges or deaths. Most studies looked at illnesses related to the cardiovascular system (heart or blood vessels), such as heart attacks and strokes. Studies also looked at effects on respiratory health, including chronic obstructive pulmonary disease (e.g. bronchitis), asthma and lung function. Seven studies looked at the health of newborn children. Eleven studies reported death rates. The best-quality studies collected data at multiple time points before and after the introduction of a ban in order to adjust for existing time trends. Some studies could compare events rates in areas with and without bans, or where bans were introduced at different times.
Key results
There is evidence that countries and their populations benefit from improved health after introducing smoking bans, importantly to do with the heart and blood vessels. We found evidence of reduced deaths. The impact of bans on respiratory health, on the health of newborn children, and on reducing the number of smokers and their cigarette use is not as clear, with some studies not detecting any reduction.
Quality of the evidence
Legislative bans have not been evaluated by randomized trials, and the quality of the evidence from the types of studies contributing to this review is lower. Changes in health outcomes could be due to other things, such as change in healthcare practices. However, many of the studies used methods of analysis that could control for underlying trends, and increase our confidence that any changes are caused by the introduction of bans.
