We can breathe easy after all. Smoking bans are linked with falls in childhood asthma attacks and premature births, according to the biggest analysis yet of the impact of public smoking bans on child health. The finding should dispel fears that such laws could have the opposite effect because they may lead people to smoke more at home.
Several countries and some US states have tightened laws on smoking in public places over the last few years. Meanwhile, some countries, such as the Netherlands and Germany, still allow smoking in pubs and restaurants or do not strictly enforce their laws. Only about half of US states have comprehensive bans, and there are few restrictions in poorer nations.
Opponents often claim that bans could result in people smoking more at home, which would be worse for their children's health. Asthma is one of the main concerns as second-hand smoke harms children's airways in several ways – by making them hypersensitive to allergens in the air, for example.
Researchers led by Jasper Been at Maastricht University Medical Centre in the Netherlands reviewed 11 studies that examined how hospital admissions for childhood asthma and preterm births changed after smoking bans came in – pregnant women who smoke are more likely to have premature babies. The studies involved more than 2.5 million births, and nearly 250,000 hospital admissions for asthma. Three studies related to the UK ban introduced between 2006 and 2007, with the rest looking at other parts of Europe or the US.
Both asthma admissions and preterm birth rates fell by about 10 per cent within a year after smoking restrictions were implemented. This was independent of any gradual changes in rates that might have been occurring anyway.
While the studies included in this meta-analysis did not investigate the mechanisms, the authors suggest that the fall in asthma admissions is a reflection of the bans making smoking less socially acceptable. "It's changing societal norms rather than the actual exposure of children in public places," says Been. It is likely that more people are banning smoking in their home, he says.
The effect on preterm births could also have been caused by pregnant women being more likely to quit or cut down following a public ban, says Been.
Been says the studies could not prove that smoking bans caused these health benefits because they were not randomised trials. However, a causal link is the most likely conclusion, he says, because the analysis included several smoking bans introduced in different countries in different years, and most saw health improvements.
Alun Blum at the University of Alabama in Tuscaloosa says such findings are useful for countries and states where there is ongoing debate about how strict smoking bans should be, especially as hospital care for premature babies is so expensive. "This might be one of the most important things to know in order to reinforce legislation," he says. "It's epidemiological eye candy."
Other studies have shown that rates of heart attack and stroke also tend to fall after smoking bans are introduced.
Journal reference: The Lancet, DOI: 1-.1016/S0140-6736(14)60082-9
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