Thursday February 4 2016
Smoking bans may benefit non-smokers' health most
The ban on smoking indoors in public places "has helped save the lives of passive smokers," says the Daily Mail.
The headline refers to a review of the effects of smoking bans in 21 countries, including England and Scotland. This found fewer admissions to hospitals for heart attacks and strokes following smoking bans. However, the bans didn't appear to encourage more people to stop smoking.
Some studies included in the review found a bigger reduction in heart attacks and strokes among non-smokers – who are no longer exposed to smoke in public places – than smokers, who are still exposed to their own smoke.
The difficulty with research into smoking bans is that you can't carry out the "gold standard" of research: a randomised controlled trial. Instead, we have to rely on observational evidence – for example, looking at trends in hospital admissions for heart attacks before and after a ban is introduced.
It's hard to prove that smoking bans have led to lower hospital admissions, rather than other things, such as putting tobacco prices up. But this research suggests they have, particularly for non-smokers.
Where did the story come from?
The study was carried out by researchers from the Cochrane Tobacco Addiction Group, which is part of the Cochrane Collaboration of international healthcare researchers. It was funded by the Health Research Board Ireland and University College Dublin. The study was published in the peer-reviewed Cochrane Database of Systematic Reviews on an open-access basis, so it is free to read online.
The Sun, Mail Online and The Daily Telegraph focused on results from the smoking ban in England, which was introduced in 2007. While they were reported accurately, these results were published in the British Medical Journal (BMJ) in 2013, so are not particularly new. The Guardian gave a good overview of the research, including links to the original studies.
What kind of research was this?
This was a systematic review of all the studies previously published on the effects of smoking bans on health. Systematic reviews are the best way to get a balanced picture of all the evidence on a topic. However, they are only as good as the studies they include.
In this case, there were no randomised controlled trials, so the researchers had to rely on observational studies of varying quality.
What did the research involve?
This research was an update of a previous systematic review of the evidence around smoking bans, published in 2010. Since then, more countries have introduced smoking bans and more studies have been published.
Researchers searched databases of published research, looking for all relevant studies that met their criteria. They then examined all the studies to record their methodology, results and assess the study for risk of bias.
Usually, Cochrane reviews carry out a meta-analysis, where they pool the data to give overall results from all the studies. Because of the different types of research they found, they were unable to do this for this review. Instead, they grouped together studies looking at the same health outcomes, then summarised the results for each group.
What were the basic results?
Researchers found 77 studies and looked at the effects of a smoking ban on:
- cardiovascular health (mainly heart attacks and strokes)
- respiratory health (mainly asthma and chronic obstructive pulmonary disease, or COPD)
- the health of newborn babies
- numbers of deaths from smoking-related diseases
- numbers of people who smoked, plus quit rates and tobacco consumption
They found "persuasive" evidence from 33 out of 43 studies that fewer people were admitted to hospitals with heart attacks and unstable angina, and evidence from five out of six studies that fewer people were admitted with stroke. Some studies found that non-smokers benefited from a bigger reduction in the incidence of heart attack and stroke.
The review also found national rates of smoking-related diseases (including heart disease) went down after smoking bans were introduced, and continued to fall. Eight out of 11 studies showed a reduction in deaths from smoking-related diseases.
The picture was mixed for respiratory health, with conflicting results from the 21 studies reviewed; some found a reduction in COPD or asthma admissions, but others did not.
The researchers found pregnant women were less likely to smoke after bans had been introduced, and some studies found fewer babies were born prematurely or with low birth weight. However, they say the quality of the evidence was too low and the study results were too conflicting to be sure.
The evidence was also unclear about the effect smoking bans had on how much people smoked, and how many smoked. While some studies showed a dip in smoking and an increase in attempts to quit just before and shortly after a smoking ban was introduced, these reductions didn't last.
As most countries were already showing a trend away from smoking, it's difficult to determine whether the bans played a part. Other factors, such as the price of tobacco and economic outlook in a country, might have affected the results.
How did the researchers interpret the results?
The researchers said the results gave "more robust support" for their previous conclusions that smoking bans were linked to better health outcomes. "There is moderate quality evidence that countries and their populations benefit from enacting national legislative smoking bans with improved health outcomes from reduced exposures to passive smoke, specifically cardiovascular disease," they said.
However, they added that the evidence for fewer deaths from smoking-related diseases was "low quality".
There is no doubt that tobacco smoking harms health and causes a great deal of disease and death. The World Health Organization (WHO) estimates that tobacco is responsible for one in 10 adult deaths worldwide.
The question is whether smoking bans can help reduce the harm caused by tobacco. This summary of research suggests they can, particularly for people who are non-smokers. While it's hard to get good-quality evidence about the effects of smoking bans, comparisons of data from hospitals and national registries before and after a ban is helpful.
However, we can't be sure the effects being measured are solely down to the smoking ban. For example, bans on trans fats in foods in some countries could also have contributed to a drop in heart attacks and stroke. However, it's useful to have information from lots of different countries, all showing similar trends over time.
The evidence around the numbers of people who stop smoking after a smoking ban is disappointing, but the researchers point out that smoking bans are only one way to encourage people to quit.
If the effects of a smoking ban are simply to protect people who don't smoke from the harmful effects of tobacco, that is still a big improvement.
Read more information and support about how to give up smoking.