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King-size cigarette,
pint-size intellect |
It's good to see Dr. Carl V. Philips back and blogging over at
Ep-ology. In his last two posts he has been discussing the
North Carolina heart miracle 'study', which is as bad a piece of advocacy-driven junk science as you will ever see.
In particular, he makes a point which I have tried to made before, which is absolutely fundamental to all the heart miracle studies. The results they report—of heart attacks falling by 17%, 21%, 40% or whatever—are simply
impossible.
Let's go along with the "consensus" view that long-term secondhand smoke exposure increases the lifetime risk of heart disease by around 20-30%. Nevermind whether that is a realistic estimate. For good or ill, it is the figure used by the Surgeon General and other authorities, and it is accepted by those who conduct the heart miracle studies.
That being the case, is it plausible that the elimination of secondhand smoke from restaurants, offices and bars could reduce the heart attack rate by 21% (as reported in North Carolina) or 40% (as reported in Helena, Montana)?
It is not.
For one thing, most restaurants, some bars and nearly all offices were non-smoking before the ban. In addition, many non-smokers avoided the few remaining smoky venues before the ban. The vast majority of heart attack cases are elderly and not the kind of people to be out partying in bars, nor indeed working in pubs or waiting tables in restaurants. Furthermore, the amount of secondhand smoke inhaled by this subsection of non-smokers before the ban is minimal compared to the long-term exposure that the 20-30% figure is based on.
As Carl explains...
How many people go from being exposed to restaurant/bar smoke to unexposed as a result of the ban? It is a bit fuzzy to define this since there will be a lot of people whose exposure is reduced, and a spectrum of how much it is reduced. But we can start with the observation that roughly half of everyone had approximately zero such exposure before the ban, never or almost never going out to eat and drink, or avoiding smoking-allowed venues when they did...
Thus, even if you believed that exposure at the level of visiting restaurants and bars causes somewhat more than 20% increase in risk, which is an absurd belief in itself, there is no possible way the effect of the smoking ban could be more than about half of the claimed 21%.
Even if we assume that secondhand smoke does cause heart attacks, smoking bans have so little effect on so few non-smokers (and have no effect at all on the smokers, unless it compels them to quit), that the kind of reductions in the heart attack rate reported by these studies defy both science and common sense. If there
is an effect, it is too small to measure and would never show up in population-level statistics. Once that is understood, it is obvious that any studies which claim a dramatic effect on the heart attack rate must be flawed, cherry-picked or distorted. Sure enough, when such studies are examined, they prove to be flawed, cherry-picked and distorted.
We can figure that half of the population was not exposed in the first place, that easily a third of those exposed were smokers, that many of those exposed had very minor and occasional exposure, and that many others that were exposed had only a minor reduction in exposure since most of their exposure was elsewhere. So it seems unlikely that even one-fifth of the population experienced a substantial reduction in exposure, getting the effect down below 1% of the total.
If, to take North Carolina as an example, the smoking ban caused the heart attack rate to drop by 21%—which it unequivocally
did not—it follows that smoking in bars, restaurants and offices must have been responsible for a fifth of all heart attacks
before the ban.
It is quite possible that thirty years of induced panic about passive smoking has persuaded many people that such diluted tobacco smoke is capable of wreaking such havoc, but the empirical evidence shows that it cannot be so. If it were, the relative risk from secondhand smoke exposure would be far higher than 20-30%. Indeed, secondhand smoke would be responsible for more heart attacks than smoking. It would mean that passive smoking (at work and at home) was the single biggest risk factor for heart attacks. Even the most tobaccophobic hypochondriac surely cannot believe such a thing.
In the case of Stanton Glantz's bar-lowering
Helena study (2004), the smoking ban effect was even greater—an astonishing 40%. Again, this implies that smoking in a subsection of private venues was responsible for two-fifths of all heart attacks before the ban—a manifestly risible idea.
Interestingly, Glantz must have known that his findings were inherently implausible because he addressed them in the text of the
study itself. His comments tell you much about the man's mathematical illiteracy and, sadly, tell us much about the decline of the peer-review process (the study was published in the prestigious
British Medical Journal). He wrote:
The effect associated with the smoke-free law may seem large but is consistent with the observed effects of secondhand smoke on cardiac disease. Secondhand smoke increases the risk of a myocardial infarction by about 30%; if all this effect were to occur immediately, we would expect a fall of - 0.30 x 40.5 = - 12.2 in admissions during the six months the law was in effect, which is within the 95% confidence interval for the estimate of the effect (a drop of - 32.2 to - 0.8 admissions).
His argument here is that secondhand smoke exposure increases the risk of heart disease by 30% and so, "if all this effect were to occur immediately", a smoking ban should reduce the heart attack rate by around 30%. 40% is, he concedes, a little higher than might be expected but it is within the margin of error.
This piece of reasoning is so patently flawed that I still cannot believe it was allowed to be published. Let's leave aside the fanciful idea that the effect of a lifetime's exposure would suddenly be nullified by a smoking ban in non-domestic settings. The key point is that Glantz ignores the fact that secondhand smoke is one of dozens, if not hundreds, of risk factors for heart attacks (or heart disease—he treats them as if they were the same thing). He seems not to comprehend the difference between relative risk and absolute risk. He does not acknowledge that a relative risk which affects a subsample of the nonsmoking population is not going to have a commensurate effect on the entire population. And he implicitly treats secondhand smoke as if it were the sole cause of heart disease. These are staggering schoolboy errors for a man with pretensions of being an epidemiologist (which just goes to show that a degree in mechanical engineering is not always the best grounding for a career in cardiology).
Look at it this way. If using a mobile phone while driving increases your risk of having an accident by 90%, what will be the effect on the number of car crashes in a country that bans the practice?
The answer is that we do not know. There are countless other risk factors for car crashes and so, even if using a mobile phone has a substantial effect on
individual risk, the effect at the
population level will be too small to measure.
By Glantz's logic, however, the effect of a mobile phone ban will be to reduce the number of car crashes by 90%—because he doesn't understand the basic difference between individual relative risk and absolute risk to the population. How can he be so ignorant? There are, as Carl says, only two possibilities.
Interestingly, it is not entirely clear whether he spouts junk because he has not acquired a modicum of understanding about the science in the field where he has worked for decades, or because he is a sociopath-level liar; I am not entirely sure which is the more charitable interpretation.
Do go read both of Carl's pieces about the North Carolina nonsense:
Unhealthful News 189 - Absurd claims about the effects of smoking place restrictions, North Carolina edition (Part 1)
Unhealthful News 190 - Absurd claims about the effects of smoking place restrictions, North Carolina edition (Part 2)
