There is a lively debate on the health impact of passive smoking (other questions on skeptics.se are here Does passive smoking kill 600,000 people every year? and here Is secondhand smoke dangerous?).
But anti-smoking health campaigners made some startling claims when various towns, regions and countries started bring in legislation to ban smoking in the workplace over the last 15 years or so. The claims are that one major result of workplace bans is that the number of heart attacks is immediately reduced. One of the more lurid reports appeared in The Scotsman in 2009 (Scotland implemented its ban earlier than England):
SMOKING bans have dramatically reduced the number of heart attacks in Europe and North America, cutting rates by between a quarter and more than a third, two major studies have shown.
The evidence suggests anti-smoking laws have had a bigger impact on heart health than first thought.
But these are big public health effects and the size seems at least a little implausible. Anti-nanny-state activists have criticised the early reports. For example, this article by Christopher Snowdon in Spiked argues:
Tales of heart attacks being ‘slashed’ by smoking bans have appeared with such regularity in recent years that it is easy to forget that there is a conspicuous lack of reliable evidence to support them.
Criticising one high estimate of the effect thus:
...one must bear in mind that around 10 to 15 per cent of coronary heart disease cases are attributed to active smoking. That passive smoking could be responsible for a further 40 per cent strains all credibility.
Note that there are several plausible reasons why over eager campaigners might inadvertently exaggerate the effect. Failing to account for natural variation or long term trends in heart attack rates might easily lead to implausibly large estimates of the effect of smoking bans. So the key question here is: do smoking bans have a noticeable effect on heart attack rates? And, if there is an effect, how big is it?
Added clarification: since heart attacks are one of the prices smokers pay for their habit we expect to see reductions in heart attacks when they give up. And more people may quit when workplace and indoor smoking is banned. The interesting question, though, is what effect is seen in non-smokers. We care more about them as it is much easier to justify legislation to prevent harm to third parties than it it is to prevent self-harm. Great care with statistics is required to clearly distinguish the two groups.
NB Although the general question has been addressed here before, I'm asking this specific one as the effect on heart attacks has not, as far as I can tell, been covered in those questions.