Effects of smoke-free workplace legislation on heart attacks

There is no doubt whatsoever that exposure to other people’s tobacco smoke pollution, over a long period of time, can cause various diseases (as summarized in a previous posts):
Health effects of Tobacco Smoke Pollution. 8/6/07
Sidestream cigarette smoke more toxic than mainstream smoke. 8/8/07
Make yours a smoke-free home. 08/10/07

Since the growing implementation of workplace smoking bans (with bars restaurants etc being workplaces) there have been a number of reports from around the world finding that the rate of hospitalizations for acute myocardial infarction (MI: a “heart attack”) decreases significantly in areas where these smoking bans are implemented.

These studies have sometimes been based on very small geographic regions and a relatively small number of MIs. For example, a widely reported study published in the BMJ in 2004 found that in Helena, Montana, the number of hospitalizations for MI fell from 40 per half-year before the workplace smoking ban to 24 in the six months the law was in effect. The MI hospitalization rate increased slightly in a part of Montana outside Helena, and increased again (to 38) in Helena when the workplace smoking ban was lifted .

This month a much larger study found that there were 3814 fewer hospital admissions (an 8% drop) for MIs in New York state in 2004 than would have been expected without the smoke-free workplace legislation implemented in 2003 in New York.

One question raised by these findings is whether the effects are caused primarily by fewer MIs in smokers who reduce or quit smoking because of the ban on smoking in workplaces, or whether it is primarily caused by fewer MIs in non-smokers who are no longer having to breath air polluted by tobacco smoke.

Another study published this month suggests that the effect is almost exclusively in non-smokers. This study by Drs Seo and Torabi of Indiana University carefully compared the number of hospitalizations in one Indiana county (Monroe) that implemented increasingly strict smoke-free workplace legislation, with another very similar county that did not pass such legislation (Delaware county). They found that in Monroe county the number of non-smoking MI admissions fell from 17 to 5, whereas it fell from 18 to 16 over the same time period in Delaware. The number of smokers admitted with MIs stayed about the same in both counties. This suggests that the reductions in MIs following these smoking bans is due to the reduction in the cardiotoxic effects of inhaling tobacco smoke pollution in non-smokers (For some reason the authors excluded MIs in people with other pre-existing risk factors such as high BP or cholesterol. I’m not sure why, so if you know, please explain it to me).

While none of the studies finding reduced MIs following smoke-free workplace legislation are perfect, and many are based on a very small number of cases, they are telling a fairly consistent story. The only way the data could fall this way by chance (rather than due to a “real” effect) would be if there was a systematic publication bias (i.e. people doing similar studies with different results not publishing them) or a systematic bias in the research process (e.g. researchers “cherry-picking” the time-frames chosen for comparisons to exclude “data blips” that don’t fit with the claimed results). While such biases do sometimes enter into the research process my inclination is to believe the results when they are almost all pointing in the same direction. So if you are aware of any studies of this issue that found different results, please let me know. But in the mean time the main conclusions appear to be:

1. Non smokers exposed to other people’s tobacco smoke pollution have increased risks of suffering a heart attack.

2. Implementing comprehensive smoke-free workplace legislation not only allows people to work in a safer workplace, it results within a year in a reduced number of non-smokers suffering from heart attacks.

3. If making workplaces smoke-free reduces heart attacks, making homes smoke-free will likely have the same effect.

Have a happy and smoke-free Thanksgiving.
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About the Author

MA, MAppSci, PhD

Dr. Jonathan Foulds is an expert in the field of tobacco addiction.