Meta-analysis of the effect of comprehensive smoke-free legislation on acute coronary events

Objective To assess the evidence for a reduced risk of acute coronary events following comprehensive smoke-free legislation. Methods Two independent systematic reviews were undertaken using PubMed, Embase and Science Direct with no date restrictions imposed. Meta-analysis was undertaken using a random effects model to obtain a pooled estimate of the relative risk. Linear regression was used to examine possible bias and meta-regression was used to investigate possible causes of heterogeneity. Main outcome measure Acute coronary events. Results The 17 eligible studies (10 from North America, 6 from Europe and 1 from Australasia) provided 35 estimates of effect size. Apart from five subgroup analyses, all of the published results suggested a reduction in the incidence of acute coronary events following the introduction of smoke-free legislation. Meta-analysis produced a pooled estimate of the relative risk of 0.90 (95% CI 0.86 to 0.94). There was significant heterogeneity (overall I-2=95.1%, p<0.001) but there was no evidence of small study bias (p=0.714). On univariate random effects meta-regression analysis, studies with longer data collection following legislation produced greater estimates of risk reduction and remained significant after adjustment for other study characteristics (adjusted coefficient -0.005, 95% CI -0.007 to -0.002, multiplicity adjusted p=0.006). Conclusions There is now a large body of evidence supporting a reduction in acute coronary events following the implementation of comprehensive smoke-free legislation, with the effect increasing over time from implementation. Countries that have not yet adopted smoke-free legislation should be encouraged to do so.