A study presented at the American Heart Association annual meeting found that smoking bans have no effect on the incidence of heart attacks during the first year after implementation.
The study, by Dr. Robin Mathews of the Duke Clinical Research Institute, examined rates of heart attacks among persons ages 65 and older in 43 cities across the U.S. which adopted strong smoking bans during the period 2000-2008. The heart attack rates were compared from one year prior to the smoking ban to the year following implementation of the smoking ban. Mathews reports that there was absolutely no change in the heart attack rates across the sample of cities. A figure shows that heart attacks decreased in some cities and increased in others. All told, heart attack rates decreased by an insignificant 1%.
When Mathews included all 74 cities that enacted smoking bans during the study period (regardless of strength of the ordinance), he found an overall decline in heart attack rates of just 3%.
The study concludes that the actual effect of smoking bans on heart attacks is much lower than has been reported in the previous literature.
The Rest of the Story
While there have been individual studies that reported a significant, and sometimes very large, decline in heart attacks in communities following the implementation of a smoking ban, every study that has systematically examined the relationship between smoking bans and heart attacks across all communities that implemented smoking bans in a given time period has found no major effect.
It seems clear that the explanation for the discrepancy is publication bias. There are many factors operating which discourage researchers from reporting "negative" findings. It is also much more difficult to get negative findings published, especially on this topic. No researchers are running out to publish a study showing no decline in heart attacks following a smoking ban.
The studies which have systematically examined the effect of smoking bans on heart attacks in all cities across the country that have implemented such bans have found that while heart attacks have declined in many cities, they have increased in others. The overall effect is nil, or very close to it. However, the only studies being published are the ones which have found a positive effect. This is a classic presentation of publication bias.
The effect is compounded by the fact that the media are less interested in covering "negative" studies (and researchers are less excited about going to the media with "negative" results). For example, the current study is a case in point. I could find no newspaper articles that reported the results of this "negative" study. In contrast, when a study with "positive" findings is presented at a scientific conference, it tends to be widely publicized.
In addition, anti-smoking groups only report the results of the "positive" studies. To the best of my knowledge, no anti-smoking group has reported the results of the Mathews study. And they won't, because it is not scientific accuracy which is driving the movement these days. I won't even go through the motions of offering my usual $100 reward to the first anti-smoking group that reports these "negative" findings because it just isn't going to happen. The interest is not in reporting the science, but in reporting "favorable" results.
The shame is that there are no "favorable" or "unfavorable" results. The truth is the truth. The science is the science.
NOTE: Christopher Snowdon has a very nice summary and commentary of this research over at Velvet Glove Irong Fist. Tim Worstall writes about the issue here in Forbes magazine.
No comments:
Post a Comment