Secondhand smoke: just a few confounders?

Smoking Ban Leads to Major Drop in Heart Attacks – NYTimes.com

Smoking bans are designed not only to cut smoking rates but also to reduce secondhand tobacco smoke. It is a widely recognized cause of lung cancer, but its effect on heart disease can be more immediate. It not only damages the lining of blood vessels, but also increases the kind of blood clotting that leads to heart attacks. Reducing exposure to smoke can quickly cut the risk of clotting, some experts said.

”You remove the final one or two links in the chain” of events leading to a heart attack, Thun said.

Secondhand smoke causes an estimated 46,000 heart disease deaths and about 3,000 lung cancer deaths among nonsmokers each year, according to statistics cited by the CDC.

In the new study, researchers reviewed hospital admissions for heart attacks in Pueblo. Patients were classified by ZIP codes. They then looked at the same data for two nearby areas that did not have bans — the area of Pueblo County outside the city and for El Paso County.

In Pueblo, the rate of heart attacks dropped from 257 per 100,000 people before the ban to 152 per 100,000 in the three years afterward. There were no significant changes in the two other areas.

On the face of it, it looks very nice, and the idea that you’re getting rid of a nasty precipitating event is attractive. But there are so many questions, not just whether the 20% reduction in smoking during the same time reduced heart attacks, or whether treatment got better. For example, what about all-cause mortality? If people are dying of congestive heart failure or emphysema or stroke or a bunch of other heart-correlated causes instead of heart attacks, you haven’t really bought yourself anything — you may even be losing ground in terms of costs. Also, what if you’re just postponing these deaths a few years, until some other precipitating event causes a fatal infarct? From the point of view of the people dying, that time is precious, but from a population-mortality point of view the rate will go right back up as soon as the deferral period is over.

Oh, and by the way, that “per 100,000” number makes it sound as if they’re working some huge sample, but in fact pueblo’s population is just about 104,000. So that’s a couple hundred heart attacks a year, period. You’d really like to see more data than that.

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