Scottish Smoking Ban Study Leads to Huge Drop in Journalistic Credibility
Jacob Sullum | November 21, 2007, 12:45pm
Two months ago, a study reporting that the imposition of Scotland's smoking ban had been followed by a 17 percent drop in hospital admissions for heart attacks prompted credulous headlines like these:
Smoking ban brings big cut in heart attacks in Scotland, study finds (The Guardian)
Smoking ban 'reduces heart risk' (BBC News)
Scottish smoking ban cuts heart attacks (The Telegraph)
Scottish Smoking Ban Leads to Huge Drop in Heart Attacks (Der Spiegel)
Now it turns out that the complete admissions data for the year following the ban show a drop less than half as big as the one claimed in the study and in all those news stories. And as Michael Blastland shows in a recent BBC News article, the 8 percent drop may simply be part of a long-term trend:
Heart attacks have been falling steadily for some years now. The percentage falls in the three years before the ban were 5.1%, 4.7% and 5.7%. So the fall since is still bigger than the trend would lead us to expect, but bigger only by about three or four percentage points—an improvement, but retreating fast from the magnitude of 17.
The latest release also makes clear that even an 8% fall in heart attacks is not unprecedented. There was another, larger drop between 1999 and 2000 of about 11%.
This seems to demonstrate significant variability around the trend, suggesting that last year's 8% drop might even be the result of chance. It is conceivable, although perhaps unlikely, that the smoking ban had no effect at all. The figures could be a result of no more than the ordinary ups and downs of statistical variation from one year to the next.
Reporters can't be expected to look at data that haven't been released yet. But the idea that a smoking ban could cause an immediate, dramatic drop in heart attacks, whether by reducing secondhand smoke exposure or by encouraging smokers to quit, is so scientifically implausible that journalists should be automatically skeptical. Random variation and/or continuation of pre-existing trends are much more likely explanations for a decrease in heart attack admissions that happens to follow the imposition of a smoking ban. In the absence of more evidence, including additional years of followup and data from other jurisdictions with smoking bans (most of which apparently have not seen the big changes found in the few places that anti-smoking activists like to cite), the breathless reports prompted by studies like this one are absurdly premature.
[via The Rest of the Story]
Paul | November 21, 2007, 2:19pm | #
Taktix:
You don't have to be a scientist to understand statistics, margins of error, statistical anomalies, dampening of said anomalies over time, or contextual health dangers vs. immediate health dangers.
For instance, if we banned the ingestion of strychnine and handling of rattlesnakes, we might see an immediate drop in related health effects. But to ban smoking or transfats in a public venue and then suggest that within one year we immediately saw a 17% reduction in heart attacks (a health effect
related to hundreds or even thousands of environmental and genetic factors) is near plain stupidity.
First, it would suggest that smoking is pretty much the only damned cause of heart disease. Second, assuming the first, it would assume that if you just banned cigarettes completely, in both public and private venues, you know, like we do cocaine, marijuana, heroin etc., then you'd see a mind-boggling drop in heart attacks. Oh, sorry, an even MORE mind-boggling drop in heart attacks. I would estimate you'd triple that percentage drop.
When my Dad was around 80 years old, he had quintuple bypass. I pressed one of the surgeons for information as to how and what my dad could to do avoid any future problems after his surgery-- in other words: what caused this, and how can he prevent it?
The surgeon, widely considered one of the better in his field responded: There are many
correlations to heart disease, but the fact of the matter is, despite what you read in the press, we simply don't know what causes it.
Now admittedly this was the mid-nineties. Maybe there's some research somewhere that says we cracked this nut, and 90% of all heart attacks are smoking related?
And if you actually read the article (a painful endeavor I must warn) they report... I hesitate to have these pixels rasterized on my screen, but here goes...
Non-smokers benefit most with 20% fall in first year
20%. Non-smokers. Marinate on that for a bit. Let that soak in. Sitting near to someone for a couple of hours a week that lights up drops your heart attack risk by 20%. Wow, imagine the drop if we could just ban cigarettes altogether? Sure even if true (can you tell I'm laughing) we would see statistical diminishing returns as we expanded the bans. But when you think about it, banning smokes in pubs and restaraunts is only a first relatively small step. There are plenty more venues which play larger roles in our lives than pubs and restaraunts, so those effects of diminishing returns won't be seen for a while.
In summary, if we banned cigarettes completely, going as far as making posession a crime, what, pray tell would we actually die from?
