February 15, 2017

Stanton A. Glantz, PhD

Smokefree Laws Cut Heart Attacks (and other bad things): Look At All The Evidence

There is strong and consistent evidence that exposure to secondhand smoke causes heart attacks and that smokefree workplace and public place laws cut heart attacks (and other diseases).
You would question that conclusion if you read the article in Slate by Jacob Grier, a one-time employee of the tobacco industry-supported Cato Institute and bartender, who tries to use the natural variability in results in different studies to argue against this fact. 
Grier begins by criticizing the first study showing such a drop, a study we did in Helena Montana, on the grounds that the drop we reported was unbelievably large.  And the observed drop was large, 40% in the final analysis.  Grier ignores the fact that Helena is a small place in which there were not many heart attack hospital admissions, so there was uncertainty in the estimate the true drop in heart attack admissions in the whole population.  While we found a 40% drop in the 6 months we studied, the true drop could have been anywhere between 1% and 79%. (This is what statisticians call the 95% confidence interval and journalists call “the margin of error.”)  The important point is that it does not include zero (i.e., no effect), so we can be confident that the drop was more than a chance finding.
Since the Helena study, there have been many studies of changes in heart attack admissions following smokefree laws.  Some found bigger effects than we did in Helena, some smaller, even no change.  This is normal in any kind of scientific study; there is always natural variation. 
The important thing to do is look at all the evidence (not just the few studies Grier talked about).
The US Surgeon General did just that, in his 2014 report The Health Consequences of Smoking – 50 Years of ProgressThe report, which goes through extensive vetting involving hundreds of scientists, looked at all the available data (35 studies of comprehensive smokefree laws, plus 14 studies of weaker laws at the time; there are more now) and concluded that there was a 15% drop in heart attack hospital admissions (with a margin of error of 12-18%). 
But, isn’t 15%ia lot smaller than 40%?  Yes.  But, the important point is that 15% is well within the 95% confidence interval we found in the original Helena study.  What all this shows is that as we get more evidence the estimates of the effect become more precise.
The drop in heart attack hospital admissions is also what would be expected based on what we know about the biology of heart attacks.  As the Surgeon General explained in her 2010 report, How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease, “Low levels of exposure, including exposures to secondhand tobacco smoke, lead to rapid and sharp increase in endothelial dysfunction and inflammation which are implicated in acute cardiovascular events and thrombosis.”  In plain English, secondhand smoke has immediate effects on blood and blood vessels in a way that both increases the risk of triggering a heart attack.
And e-cigarettes have already been shown to have the same bad effects on blood vessels (study1,  study2), heart rhythm, and other ways.
 That’s not all.  Hospitalizations for asthma and other lung disease drops, too.
These effects are so big and fast that Colorado saw a 20% drop in ambulance calls when it enacted its state smokefree law (everywhere but casinos, which were exempted).  Two years later, when the law was extended to casinos, ambulance calls dropped by 20% there too, catching up with the rest of the state.
Smokefree laws save lives and they do it quickly.
Stanton A. Glantz is Professor of Medicine (Cardiology) and Director of the Center for Tobacco Control Research and Education at the University of California San Francisco.  He has published over 375 peer reviewed papers and several books, including The Cigarette Papers, Tobacco War, and Bad Acts, as well as two statistics texts.  He is a member of the National Academy of Medicine.

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