Monday, November 02, 2009

Published Study Shows No Effect of New Zealand Smoking Ban on Acute Cardiac Events During First Year; Study Not Considered by IOM Committee Report

A peer-reviewed study published in the journal Tobacco Control reports no effect of New Zealand's smoking ban on admissions for acute cardiac events during the first year the law was in force (see: Edwards R, et al. After the smoke has cleared: evaluation of the impact of a new national smoke-free law in New Zealand. Tobacco Control 2008; 17:e2).

On December 10, 2004, New Zealand's existing smoke-free workplace law was amended to include all restaurants, bars, casinos, and clubs. The law resulted in significant declines in secondhand smoke exposure during the first year of implementation, and it affected a large population of 4.3 million people. There is a stable, national data collection system that covers all hospitals. All of these factors make this study population an ideal one to examine the relationship between the implementation of the smoking ban and acute changes in hospital admissions for acute cardiac events.

The study examined national data on hospitalizations for heart attacks and unstable angina from the New Zealand Health Information Service for the seven years prior to the smoking ban and one year following the ban. Poisson regression analysis was used to model the trends in hospitalization rates and to determine the significance of observed changes in hospitalization rates following implementation of the smoking ban.

In the year following the smoking ban, the rate of hospitalization for acute myocardial infarctions (heart attacks) increased in New Zealand. There was no significant difference in the pre- and post-ban trends.

Unstable angina admissions decreased in the year after the smoking ban, but there was no significant difference in the pre- and post-ban trends in the Poisson regression analysis.

When combining heart attacks and unstable angina to look at trends in the rate for all acute coronary events (also known as acute coronary syndrome), there was no significant change in acute coronary events from before to after the smoking ban, and no significant difference in the pre- and post-ban trends in the Poisson regression analysis.

The paper concludes: "There was therefore no clear evidence that the hospitalisation rate for these health outcomes reduced in the first 12 months after implementation of the SEAA [Smoke-free Environments Amendment Act]."

The Rest of the Story

While this is a published study that fails to find any significant effect of a national smoking ban in New Zealand on heart attack admissions, this paper was not considered - or even mentioned - in the Institute of Medicine (IOM) report that purported to review all published studies that examined the effect of smoking bans on heart attacks.

It would therefore be more accurate to say that the IOM committee reviewed all published studies which reported a significant effect of smoking bans on heart attacks, but excluded a critical published study that failed to support the report's conclusion.

The IOM committee has defended its failure to consider important data from Scotland, England, Wales, Iceland, several U.S. states, and the U.S. as a whole by arguing that such data are unpublished (even though these data are simply unbiased hospital figures). Here, however, the committee can no longer provide the same defense, since these data were published in a reputable peer-reviewed journal.

The population covered in this study is huge - 4.3 million people. Thus, it provides much more reliable information than the results from small communities like Helena (25,000), Pueblo (157,000), and Bowling Green (55,000).

The New Zealand results add evidence to my previous assertion that the only studies to have found large effects of smoking bans on heart attacks are in very small communities, and that these results are therefore most likely due to chance. Every time a large population has been studied, there has either been no effect or such a small effect that it cannot be differentiated from underlying secular trends in heart attacks, which have generally been declining, even in the absence of smoking bans.

The rest of the story is that we have here a published study which reports no short-term effect of a national smoking ban in New Zealand on heart attack rates. The study itself concludes that there is no evidence of any effect of the smoking ban on heart attack rates during the first year of implementation. Will the anti-smoking groups which have communicated to the public the results of positive studies now share the findings of this negative study?

I challenge the anti-smoking groups which reported the results of the Helena, Pueblo, Bowling Green, or other studies, and/or which reported the results of the IOM report to disclose to the public the results of this study, which fails to show any short-term effect of a national smoking ban on heart attacks.

I don't think any anti-smoking group will take this challenge, however. Why? Because I don't think that these groups really care about the scientific truth. I think they only care about sharing science when it is favorable to their cause and when it confirms their pre-determined conclusions.

In fact, I am so confident that no anti-smoking group will disseminate the results of the New Zealand study that I will back up my challenge by offering a $100 cash reward to the first anti-smoking group that shares the negative New Zealand results publicly on its web site.

I have been arguing for a long time that disseminating these premature conclusions - derived largely from shoddy science - is a huge mistake because eventually larger studies would come out which refuted these claims. Well now that is exactly what is starting to happen. But unfortunately, anti-smoking groups have tied the need for smoking bans to these data about dramatic, immediate effects on heart attacks. Now that this no longer appears to be the case, it hurts our arguments for smoke-free laws, because we've tied these laws to decreased heart attacks.

There are substantial, dramatic, short-term health effects from smoking bans, due not to the immediate reduction of heart attacks, but to the improvement of workers' respiratory health. There are marked improvements in these workers ability to breathe. That, in my view, is enough to support the smoking bans. But by tying them to the purported dramatic effects on heart attacks, we've now weakened our case substantially. What are we going to say now, that it doesn't matter whether smoking bans reduce heart attacks? I'm afraid it's too late for that. We've kind of put our foot in our mouths. That's what can happen when you let scientific integrity go by the wayside. Better to stick to solid science in the first place and refrain from drawing sweeping conclusions before there is enough evidence to support those conclusions.

No comments: