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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.

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Without being at all involved in the debate, is the claim exclusively that reduced passive smoking is responsible for the reduction in heart attacks? I find it equally plausible that workplace smoking bans have a direct effect on the prevalence of active smoking and heart attacks related to that. –  Konrad Rudolph Dec 19 '12 at 13:14
    
@KonradRudolph That is a good clarification. My intent was to judge the effect on non-smokers. One possible confounding effect that exaggerates the estimate for them is that some smokers give up, which reduces their heart attack rate. A good answer to the question will need to carefully distinguish these effects. –  matt_black Dec 19 '12 at 15:19
    
@matt I’d argue that more important (in numbers) than those who give up altogether are those whose health improves because they cannot smoke incessantly any more – they either need to take breaks or abstain from smoking during the day. I conjecture that this makes a huge difference – both on the individual and on the population level. –  Konrad Rudolph Dec 19 '12 at 15:21
    
@KonradRudolph You may be right, but many of the reports on the effects didn't make a clear distinction and exaggerated the impact on non-smokers as a result. Good answers will make this clear. –  matt_black Dec 19 '12 at 15:49
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4 Answers

There is good evidence that smoking bans reduce the number of heart attacks. In the meta-analysis "Cardiovascular effect of bans on smoking in public places: a systematic review and meta-analysis" published in 2009 in the Journal of the American College of Cardiology the authors state in their conclusion

Using 11 reports from 10 study locations, AMI risk decreased by 17% overall (IRR: 0.83, 95% CI: 0.75 to 0.92), with the greatest effect among younger individuals and nonsmokers.

and

Smoking bans in public places and workplaces are significantly associated with a reduction in AMI incidence, particularly if enforced over several years.

AMI in this context means acute myocardial infarction, which is what is commonly known as heart attack.

They used 11 different studies in this meta-analysis. The authors further state

These studies include nearly 24 million people, observed 215,524 cardiac events, and suggest that community smoking bans are associated with a 17% reduction in AMI incidence. If this association represents a cause-andeffect relationship, and assuming approximately 920,000 incident AMIs each year in the U.S., a nationwide ban on public smoking might ultimately prevent as many as 156,400 new AMIs yearly.

From the INTERHEART study, a large study with 24767 people from 52 countries:

One of the most important risk factors for acute myocardial infarction in our study was smoking, which accounts for about 36% of the PAR of acute myocardial infarction worldwide (and about 44% in men)

So the claim that only 10-15% of coronary heart disease are attributed to smoking seems to be wrong.

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My concern about the meta-analysis estimate is that is produces a number essentially as large as the number for active-smokers which just doesn't seem right. I haven't checked the detail, though. –  matt_black Dec 19 '12 at 15:15
    
@matt_black I added a study that contradicts the statement about 10-15% of coronary heart disease are attributed to smoking. –  Fabian Dec 19 '12 at 15:31
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Yes there is an effect but it may not be as large as early studies suggested with a result of reducing heart attacks by 3-4% in some population subgroups

The trouble with science in areas where there is a broad consensus is that many people don't check their results carefully when they agree with the consensus view. And when those results can be used as public health propaganda, there is a large does of overeager confirmation bias to account for. This effect may explain some of the results reported.

Normally to get a good view of multiple studies we would use a meta analysis (and Fabian reports the results of one in his answer). The best meta-analyses in medical science are those done by the Cochrane Collaboration. Their latest review of the effects of smoking bans was conducted in 2009. Their general conclusion is worth quoting (my emphasis):

Introduction of a legislative smoking ban does lead to a reduction in exposure to passive smoking. Hospitality workers experienced a greater reduction in exposure to SHS [second hand smoke] after implementing the ban compared to the general population. There is limited evidence about the impact on active smoking but the trend is downwards. There is some evidence of an improvement in health outcomes. The strongest evidence is the reduction seen in admissions for acute coronary syndrome.

But they also concluded:

More research on the impact of smoking bans on active smoking is warranted. Whilst more comprehensive bans are now being enacted in many jurisdictions, there is also a need for research into the extent to which exposure to SHS in non-smoking areas is a result of smoke coming from the outdoor smoking areas. Further studies should utilise larger sample sizes with common agreed measures for smoking behaviour and exposure to SHS of the study population. The lack of a reference group in many studies means that it is difficult to differentiate between secular trends and impact of the intervention...

The review was not, however, focussed on the heart attack issue (it covered many effects of legislation) and only looked at 12 studies where the impact on heart attacks were measured. Some of these were small.

More recently a high quality study has appeared in the BMJ which overcomes some of the issues with previous studies partially because comprehensive population-wide data is accessible from the English NHS hospital activity statistics which are collected centrally. They conclude:

After adjustment for secular and seasonal trends and variation in population size, there was a small but significant reduction in the number of emergency admissions for myocardial infarction after the implementation of smoke-free legislation (−2.4%, 95% confidence interval −4.06% to −0.66%, P=0.007). This equates to 1200 fewer emergency admissions for myocardial infarction (1600 including readmissions) in the first year after legislation. The reduction in admissions was significant in men (3.1%, P=0.001) and women (3.8%, P=0.007) aged 60 and over, and men (3.5%, P<0.01) but not women (2.5% P=0.38) aged under 60.

Their result is statistically reliable but much smaller than many of the earler reports. They report:

The largest impacts have been reported in smaller studies in the United States, with reported reductions in the range of 27-40%, while larger studies have reported more modest reductions: 8% in the state of New York, 13% in four Italian regions, and 17% in Scotland.

But the quality of some previous studies is suspect for a variety of reasons:

There is some uncertainty around the extent to which some of these studies have effectively accounted for other factors that might influence patterns of admissions for myocardial infarction. Firstly, admissions for coronary heart disease have been declining across Europe, the US, and Canada, and failure to account for this might lead to an overestimation of impacts. Secondly, other factors such as season, flu, and temperature have all been shown to influence the incidence of myocardial infarction with, for example, peak admission rates in winter, in spring, and over the Christmas break, and seen in association with high flu rates and low temperatures.

The BMJ paper tried to address as many of these as possible by careful design and analysis. The biggest remaining confounding factor is the effect derived from smoking quitters which is hard to separate as English hospital records don't include smoking status.

The conclusion seems to be that careful statistical analysis shows a real effect on the heart attack rate (AMI (acute myocardial infarction) admissions down by a few percent), but nothing like the large gains claimed by public health activists in the early days of legislation.

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The authors state "The smaller fall detected in England, compared with that observed elsewhere, probably reflects both the lower levels of exposure to secondhand smoke before the legislation and the fact that we accounted for underlying declines in admissions for myocardial infarction and other measurable confounders". They are not attributing the smaller effect they measured solely on the design of the study. –  Fabian Dec 23 '12 at 11:26
    
@Fabian fair point, but I was pointing out that they were much more careful in their adjustments than many others. It is possible, but speculative, that the larger falls observed elsewhere were a real effect due to, for example, worse exposure before the bans. –  matt_black Dec 23 '12 at 17:56
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They have created a fear that is based on nothing’’ World-renowned pulmonologist, president of the prestigious Research Institute Necker for the last decade, Professor Philippe Even, now retired, tells us that he’s convinced of the absence of harm from passive smoking. A shocking interview.

What do the studies on passive smoking tell us?

PHILIPPE EVEN. There are about a hundred studies on the issue. First surprise: 40% of them claim a total absence of harmful effects of passive smoking on health. The remaining 60% estimate that the cancer risk is multiplied by 0.02 for the most optimistic and by 0.15 for the more pessimistic … compared to a risk multiplied by 10 or 20 for active smoking! It is therefore negligible. Clearly, the harm is either nonexistent, or it is extremely low.

It is an indisputable scientific fact. Anti-tobacco associations report 3 000-6 000 deaths per year in France ...

I am curious to know their sources. No study has ever produced such a result.

Many experts argue that passive smoking is also responsible for cardiovascular disease and other asthma attacks. Not you?

They don’t base it on any solid scientific evidence. Take the case of cardiovascular diseases: the four main causes are obesity, high cholesterol, hypertension and diabetes. To determine whether passive smoking is an aggravating factor, there should be a study on people who have none of these four symptoms. But this was never done. Regarding chronic bronchitis, although the role of active smoking is undeniable, that of passive smoking is yet to be proven. For asthma, it is indeed a contributing factor ... but not greater than pollen!

The purpose of the ban on smoking in public places, however, was to protect non-smokers. It was thus based on nothing?

Absolutely nothing! The psychosis began with the publication of a report by the IARC, International Agency for Research on Cancer, which depends on the WHO (Editor's note: World Health Organization). The report released in 2002 says it is now proven that passive smoking carries serious health risks, but without showing the evidence. Where are the data? What was the methodology? It's everything but a scientific approach. It was creating fear that is not based on anything.

Why would anti-tobacco organizations wave a threat that does not exist? ...

The anti-smoking campaigns and higher cigarette prices having failed, they had to find a new way to lower the number of smokers. By waving the threat of passive smoking, they found a tool that really works: social pressure. In good faith, non-smokers felt in danger and started to stand up against smokers. As a result, passive smoking has become a public health problem, paving the way for the Evin Law and the decree banning smoking in public places. The cause may be good, but I do not think it is good to legislate on a lie. And the worst part is that it does not work: since the entry into force of the decree, cigarette sales are rising again.

Why not speak up earlier?

As a civil servant, dean of the largest medical faculty in France, I was held to confidentiality. If I had deviated from official positions, I would have had to pay the consequences. Today, I am a free man.

Le Parisien ...

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It is fine to quote opinions and I might even agree with what he says on cancer. That isn't the question. And since two other answers have supplied exactly the evidence that Philip Even denies exists about cardiovascular effects, I'm not sure how helpful the rest of the answer is. I'm skeptical about the effects of passive smoking, but this answer doesn't contribute any actual evidence. –  matt_black Dec 24 '12 at 17:48
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From the listing below one can well see smoking bans have no impact on AMI at all and the headlines are so fallicous as to leave the ignorant even more ignorant as the anti-smoking cartel want. Beleive our studies their true they claim while making even more and more INSANE claims............Its time the anti-smoking mythology was exposed and these smoking ban laws REPEALED!

http://www.gallup.com/poll/150779/Smoking-Rates-Remain-Highest-Kentucky-Lowest-Utah.aspx

http://apps.nccd.cdc.gov/brfss/display.asp?state=VT&cat=CV&yr=0&qkey=5001&grp=0&SUBMIT4=Go

Kentucky Year: % CI n no smoking ban 2005 6.1 (5.4-6.8) 509

2006 6.6 (5.8-7.4) 552

2007 6.0 (5.4-6.6) 601

2008 5.4 (4.9-5.9) 641

2009 5.9 (5.2-6.6) 789

2010 6.0 (5.3-6.8) 690

Utah smoking ban Year: % CI n 2005 2.6 (2.1-3.1) 189

2006 2.9 (2.4-3.4) 217

2007 2.8 (2.4-3.2) 219

2008 3.3 (2.8-3.9) 262

2009 2.7 (2.3-3.0) 440

2010 2.8 (2.4-3.2) 436

..........................

Missouri no smoking ban Year: % CI n 2005 5.2 (4.5-5.9) 373

2006 5.8 (4.9-6.7) 404

2007 4.7 (4.1-5.3) 374

2008 5.3 (4.6-6.0) 389

2009 4.4 (3.8-5.0) 349

2010 4.6 (3.9-5.2) 430

California smoking ban California has 4 million smokers the most of any state its ban enacted in 1998 and you can see AMI's went thru the roof after ten years Year: % CI n 2005 3.1 (2.6-3.6) 234

2006 3.8 (3.2-4.4) 270

2007 3.1 (2.5-3.7) 241

2008 3.2 (2.8-3.6) 530

2009 3.3 (3.0-3.6) 817

2010 3.5 (3.2-3.8) 910

........................

Oklahoma Year: % CI n smoking ban 2005 5.3 (4.7-5.9) 1049

2006 5.9 (5.3-6.5) 519

2007 5.8 (5.2-6.4) 556

2008 5.6 (5.0-6.1) 610

2009 5.2 (4.7-5.8) 603

2010 5.6 (5.1-6.2) 616

Hawaii Year: % CI n smoking ban 2005 3.6 (3.0-4.2) 260

2006 3.3 (2.8-3.8) 254

2007 3.6 (3.0-4.2) 271

2008 3.3 (2.7-3.9) 267

2009 2.9 (2.4-3.4) 263

2010 2.9 (2.5-3.4) 288

.............................

Louisiana smoking ban Year: % CI n 2005 4.6 (3.8-5.4) 147

2006 4.1 (3.6-4.6) 361

2007 4.9 (4.1-5.7) 392

2008 5.3 (4.7-5.9) 395

2009 4.4 (3.9-4.8) 597

2010 5.2 (4.5-5.8) 492

North Dakota smoking ban Year: % CI n 2005 4.4 (3.7-5.1) 190

2006 4.0 (3.4-4.6) 268

2007 3.9 (3.3-4.5) 243

2008 4.2 (3.6-4.7) 282

2009 3.9 (3.4-4.4) 255

2010 4.2 (3.6-4.8) 273

...........................

Mississippi no smoking ban Year: % CI n 2005 5.2 (4.5-5.9) 289

2006 5.0 (4.4-5.6) 401

2007 4.6 (4.0-5.2) 511

2008 4.9 (4.4-5.4) 574

2009 4.9 (4.5-5.4) 802

2010 5.4 (4.8-6.0) 615

Massachusetts smoking ban Year: % CI n 2005 4.2 (3.7-4.7) 454

2006 4.0 (3.6-4.4) 685

2007 3.9 (3.5-4.3) 1262

2008 3.7 (3.3-4.1) 1153

2009 4.0 (3.6-4.3) 942

2010 4.0 (3.7-4.4) 987

.......................

Arkansas smoking ban Year: % CI n 2005 5.0 (4.4-5.6) 318

2006 5.5 (4.9-6.1) 381

2007 5.1 (4.5-5.7) 381

2008 5.4 (4.8-6.1) 428

2009 5.2 (4.4-6.1) 299

2010 5.4 (4.6-6.1) 353

Minnesota smoking ban Year: % CI n 2005 3.2 (2.6-3.8) 127

2006 3.4 (2.9-3.9) 202

2007 3.6 (3.0-4.2) 247

2008 4.2 (3.6-4.8) 249

2009 2.9 (2.5-3.3) 271

2010 3.4 (2.9-3.9) 423

..........................

Ohio smoking ban Year: % CI n 2005 4.5 (3.8-5.2) 435

2006 5.3 (4.3-6.3) 400

2007 5.4 (5.0-5.8) 819

2008 4.9 (4.4-5.3) 894

2009 4.4 (4.0-4.9) 639

2010 4.3 (3.9-4.8) 625

New Hampshire smoking ban Year: % CI n 2005 3.8 (3.3-4.3) 279

2006 4.0 (3.5-4.5) 321

2007 4.2 (3.6-4.8) 328

2008 3.8 (3.3-4.4) 386

2009 3.5 (3.0-4.0) 296

2010 4.0 (3.5-4.5) 360

............................

Tennessee smoking ban Year: % CI n 2005 5.1 (4.4-5.8) 291

2006 5.9 (5.0-6.8) 302

2007 5.5 (4.3-6.7) 368

2008 5.5 (4.8-6.2) 401

2009 4.7 (4.1-5.4) 395

2010 5.2 (4.5-5.9) 454

Idaho no staewide ban Year: % CI n 2005 4.2 (3.6-4.8) 302

2006 3.6 (3.1-4.1) 255

2007 4.2 (3.6-4.8) 298

2008 4.3 (3.7-4.9) 300

2009 3.6 (3.1-4.2) 301

2010 3.9 (3.4-4.4) 431

.......................

Alabama Year: % CI n no smoking ban 2005 5.4 (4.6-6.2) 206

2006 6.9 (5.9-7.9) 265

2007 4.9 (4.3-5.5) 449

2008 5.8 (5.1-6.6) 487

2009 5.5 (4.7-6.3) 465

2010 6.0 (5.3-6.7) 583

New Jersey smoking ban Year: % CI n 2005 3.9 (3.5-4.3) 676

2006 3.9 (3.5-4.3) 750

2007 3.9 (3.3-4.5) 430

2008 4.2 (3.7-4.6) 643

2009 3.6 (3.1-4.0) 567

2010 3.8 (3.3-4.2) 632

........................

West Virginia no smoking ban Year: % CI n 2005 7.0 (6.1-7.9) 281

2006 7.5 (6.7-8.3) 349

2007 6.0 (5.2-6.8) 334

2008 7.7 (6.8-8.5) 401

2009 6.5 (5.8-7.2) 400

2010 6.3 (5.6-7.1) 359

Oregon smoking ban Year: % CI n 2005 3.6 (3.2-4.0) 559

2006 3.8 (3.3-4.3) 242

2007 3.2 (2.6-3.8) 224

2008 3.7 (3.1-4.2) 257

2009 4.0 (3.4-4.7) 262

2010 3.5 (3.1-4.0) 310

........................

Indiana now has a smoking ban Year: % CI n 2005 5.0 (4.4-5.6) 312

2006 5.3 (4.7-5.9) 427

2007 5.2 (4.6-5.8) 380

2008 5.0 (4.3-5.7) 325

2009 4.9 (4.4-5.5) 629

2010 5.3 (4.7-5.8) 768

Vermont smoking ban Year: % CI n 2005 3.9 (3.4-4.4) 309

2006 4.0 (3.5-4.5) 353

2007 4.2 (3.6-4.8) 363

2008 4.2 (3.7-4.6) 358

2009 3.7 (3.2-4.1) 337

2010 3.7 (3.3-4.1) 376

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No point in just quoting numbers. Context matters as do the adjustments to remove seasonality and population factors. I'm skeptical about the size of some claimed effects, but this is just a rant with numbers. Either make a clear argument that puts numbers in context and explains other observations or expect more downvotes than mine. –  matt_black Dec 24 '12 at 17:31
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