Tuesday, January 12, 2010

Published Study Finds No Effect of Smoking Ban on Heart Attacks in Tuscany, Italy in First Year After Ban

A peer-reviewed study published in the European Journal of Epidemiology has concluded that there was no significant effect of the smoking ban in Tuscany, Italy on heart attacks during the first year of implementation (see: Gasparrini A, Gorini G, Barchielli A. On the relationship between smoking bans and incidence of acute myocardial infarction. European Journal of Epidemiology 2009; 24:597-602).

This is the first published study to report no significant effect of a smoking ban on heart attacks.

The smoking ban in Italy went into effect on January 10, 2005. The investigators compared incident cases of acute myocardial infarction (heart attacks) among the Tuscany population (which is about 3.6 million) during the five-year period before the ban (2000-2004) with the number of cases during the first year after the ban (2005).

Monthly, age-standardized rates for acute myocardial infarction were determined for the entire study period and a Poisson regression model was used to assess the significance of any changes in heart attack incidence during 2005 compared to the baseline period. The analysis controlled for seasonality, long-term trends, and changes in the age distribution of the population.

Two models were tested: a linear model and a non-linear model. In the linear model, the authors found that the smoking ban was associated with a non-significant 5.4% reduction in the heart attack rate in 2005. In the non-linear model, the authors found that the smoking ban was associated with no effect whatsoever on heart attack rates (a non-significant 1% increase).

The article concludes: "Differently from the results published to date, this study did not find a comparable effect of the smoke-free law on the incidence of AMI [acute myocardial infarction] during the first year after the implementation of the ban. Our estimate and the related uncertainty suggest that the expected reduction is likely to be lower. ... The estimate of the effect of the ban seems to be highly sensitive to the model specification and to the effects of unaccounted factors which could modify the trend of AMI incidence, such as changes in the prevalence of other risk factors or the modification of diagnostic criteria. Several arguments which are put forward to inspect the causal relation between smoking bans and AMI indicate that the plausible effects could be lower than the estimates reported so far."

The authors close by stating: "The implementation of smoking bans in public places represents a milestone in the history of public health. The relationship with a decrease of both active and passive smoke is unquestionable, with conclusive evidences on the reductions of a number of health outcomes after the enforcement. In particular, a decrease of cardiovascular events in the long run is expected, given the conclusive association with chronic SHS exposure. On the other hand, the estimate of the short-term effect of smoking bans on cardiovascular diseases is still uncertain, and the range of reduction showed by some of the studies published to date is likely to be an overestimate, not consistent with previous knowledge about the burden of cardiovascular diseases attributable to SHS. Moreover, several other factors, like changes in diagnostic criteria, have a strong influence on the trend of cardiovascular diseases, and it seems very problematic to properly control for their effects with this study design. Nonetheless, as this study has shown, the resulting bias could be substantial."

The Rest of the Story

This study has a number of important strengths compared to the previous literature on this research question. First, it covers a large population of about 5.6 million people. The results are based on a total of 13,456 new cases of myocardial infarction. This compares with only 304 heart attacks in the Helena study.

A second advantage of this study is that the identification of heart attack cases is based on a registry (the Acute Myocardial Infarction Registry of Tuscany), which provides consistent surveillance for heart attacks occurring throughout the study period. This differs from studies such as the one in Scotland, where different methods were used to identify heart attacks occurring pre-ban and post-ban.

Perhaps the most important strength of the study is that it included a reasonable baseline period of five years, rather than just one or two years prior to the implementation of the smoking ban, which was the case in many of the previous studies.

A final strength of this study is that it considered both linear and non-linear trends in heart attacks to model the results. But it is important to note that even with a linear trend assumption, the study found no significant effect of the smoking ban and the estimated magnitude of the association was quite small (just 5.4%).

Importantly, this published study was not considered by the Institute of Medicine committee which reviewed this issue and released its report in October of last year. It was also not considered in published meta-analyses on this topic. Because of the high sample size of this study, it is likely that inclusion of this study in the previous meta-analyses would have negated their results.

While one study does not prove or disprove a hypothesis (one always needs to look at the totality of the evidence), this study is important because it is not consistent with the conclusions that have been widely disseminated by anti-smoking groups. The interesting thing to observe will be whether or not these findings are even reported by these groups.

Based on my experience in the anti-smoking movement, I am willing to bet that not a single group which previously reported the results of studies "favorable" to their cause will now report the results of this negative study. In fact, I'm so sure that no group will do this that I am putting up a $100 reward for the first group that does. I will contribute $100 to the first anti-smoking organization that previously reported the results of one of the positive studies and which now reports the results of this negative study.

I'm not worried about losing my money because as I've recently learned, it's not the quality of the science or the truth that is important. It's the favorability of the findings. Anti-smoking groups have largely lost their scientific base and scientific integrity and they are now turning into propaganda machines which are only interested in disseminating findings that are favorable to their cause. They will not share unfavorable findings because the ultimate goal is not the truth and the scientific facts, but the supporting of the agenda.

I'd love to be proven wrong. It can be done simply by emailing me the link to an anti-smoking group's dissemination of the results of the Tuscany study. I'll be waiting.

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