Updating the evidence relating smoking bans to incidence of heart disease.

In our latest update of the evidence on smoking bans and heart disease we summarize 59 studies. We take account of the underlying trends in incidence rates as far as possible by using control data in eight studies, and by adjustment based on observed trends in cases pre- and post-ban in 40 studies, being unable to make an adjustment in the remaining 11 studies. Overall, based on 62 independent estimates from the 59 studies, we estimate that bans reduce incidence by 5.0% (95% CI 3.2-6.8%), though this estimate reduces to 2.9% (0.01-5.6%) when we exclude regional estimates where national estimates are available, and studies where trend adjustment is not possible. For 25 of the studies, quadratic rather than linear adjustment is possible, but this hardly affects the overall estimates. Ban effects are somewhat greater when the pre-ban period studied is relatively short, and in smaller studies. We compare our findings with those in other recent reviews, one of which totally ignored underlying trends and results from control populations. We discuss reasons why we believe there is likely to be a true small effect of smoking bans, and weaknesses in the data which preclude reaching any very confident conclusion.