Wednesday, April 14, 2010

Yet another smoking ban miracle study

According to a study published by the CMAJ (Canadian Medical Association Journal) and distributed widely by the Canadian news media, hospitalizations for cardiovascular and respiratory conditions dropped significantly after a restaurant smoking ban came into effect. The claim is that there was a 17 per cent drop in hospitalizations due to heart attacks in Toronto and a nearly 40 per cent decrease in hospitalizations for cardiovascular events in general.

Imagine that. Another smoking ban miracle . . . right here in my own back yard.

At any rate, according to study authors: “We calculated crude rates of admission to hospital in Toronto, Ontario, from January 1996 (three years before the first phase of a smoking ban was implemented) to March 2006 (two years after the last phase was implemented.”

That may not be entirely correct. The ban implemented in 1999 was meant to integrate already existing by-laws which were in effect when Toronto and five surrounding municipalities were amalgamated to form the new mega-city of Toronto.

And, as noted by the study authors, the smoking ban was implemented in stages. Effective 1999, smoking was restricted in public places, including restaurants, bars, billiard halls, bingo halls, bowling alleys, casinos, slots, etc. But, DSAs (Designated Smoking Areas) occupying maximum 25% of floor space were acceptable.

In June, 2001, more stringent rules were implemented in restaurants and bowling alleys with only designated smoking rooms (DSRs) permitted. Then, in June, 2004, following the anti-smoker tactic of incrementalism, the DSR rule was applied to all venues; restaurants, bars, billiard halls, bowling alleys, casinos, slots, etc. DSRs were restricted to a maximum 25% of seating area/floor space. In bingo halls, DSRs were restricted to a maximum 50% of floor space.

That right, folks, under the no smoking by-law enacted in 1999, right up until 2006, smokers were still being allowed to come in from the cold.

So what does this study actually show? If the partial bans were working so well, why was it necessary to toss smokers into the street?

Study authors note that “crude rates of admission to hospital because of cardiovascular conditions decreased by 39% and admissions because of respiratory conditions decreased by 33% during the ban period affecting restaurant settings. No consistent reductions in these rates were evident after smoking bans affecting other settings.”

But, these declines took place over a 10 year period. So, the average annual decrease in hospital admissions was 3.9%, 3.3% and 1.7% for cardiovascular disease, respiratory conditions and myocardial infarction respectively.

The study also notes that it has not proven a causal relation and acknowledged that the type of study used could not be restricted to the non-smoking population. “However, the ecological design of this study prevents the delineation of individual smoking status and other individual-level information, such as actual exposure to second-hand smoke and other risk factors (e.g., prior acute myocardial infarction and other comorbidities).”

The authors are quite frank in admitting that the study has its limitations; that smoking bans are only one factor involved in the observed decline in hospital admissions. Additional factors include increases in taxes on tobacco, tightened restrictions on advertising, the addition of graphic warnings to cigarette packaging and removal of smoking-related products from point-of-sale displays.

The point is simply that the decrease in hospital admissions may have resulted from factors other than the smoking ban.

But, as usual in these kinds of studies, the very real inadequacies in methodology and interpretation become all too apparent when they come under the scrutiny of knowledgeable experts in the field. And, the experts aren't convinced that the study has merit.

For example, anti-smoking advocate Dr. Michael Siegel notes on his blog that: “There are huge problems with this study.”

Siegel notes on his blog that similar declines in admissions for cardiovascular disease occurred in both cities used as controls in the study (Thunder Bay and Durham Region).

Hospital admissions for angina in Durham dropped by 53% between 2001 and 2004. A similar trend was evident in Thunder Bay where admissions for angina dropped by 43% between 2000 and 2006. Quipped Siegel: “The same reasoning used by this paper to conclude that the smoking ban led to the observed decline in angina in Toronto would also argue that the 53% decline in angina admissions in Durham Region was attributable to the absence of a smoking ban.”

Also ignored in the study was the fact that stroke admissions in Durham declined by 47% from 2000-2006. And, from 2003 to 2006, there was a 28% decline in heart attack admissions in Thunder Bay. So we have similar declines in hospital admissions for cardiovascular disease in the Lakehead and Durham, despite the fact that neither community had smoking bans in effect.

According to Siegel: “The rest of the story is that we have yet another study purporting to show a dramatic and immediate effect of smoking bans on acute cardiovascular event admissions which turns out to be severely flawed. In this case, the data presented in the paper (or at least in the appendix) not only fail to support the study conclusion, but they actually refute that conclusion.”

Yet few media accounts commented on these aspects of the study. They largely ignored the limitations noted by the study authors themselves, and focused on the more sensational, seemingly larger numbers over the ten year period of the study, concluding that “smoking bans may be paying big health dividends.” They simply ignored evidence suggesting that they may not do anything of the kind.

What this study points out is that the anti-smoker brigade is desperate to show that smoking bans have a significant beneficial impact on public health.

And, this one, like so many others in recent years, just doesn't cut it.

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