The introduction of laws banning smoking in public places and workplaces in North America and Europe has been quickly followed by large drops in rates of preterm births and children attending hospital for asthma, according to the first systematic review and meta-analysis examining the effect of smoke-free legislation on child health, published in The Lancet.

The analysis of 11 studies done in North America and Europe, involving more than 2.5 million births, and nearly 250 000 asthma exacerbations, showed that rates of both preterm births and hospital attendance for asthma were reduced by 10% within a year of smoke-free laws coming into effect.

Currently only 16% of the world’s population is covered by comprehensive smoke-free laws, and 40% of children worldwide are regularly exposed to second-hand smoke. To date, most studies have looked at the impact of smoking bans on adult outcomes, but children account for more than a quarter of all deaths and over half of all healthy years of life lost due to exposure to second-hand smoke.

After searching systematically for both published and unpublished studies over 38 years (1975–2013) reporting on the impact of public smoking restrictions on health outcomes in children aged 12 years or younger, Dr Jasper Been from the Maastricht University Medical Centre, in the Netherlands, and colleagues identified 11 suitable studies—five North American studies describing local bans and six European studies looking at national bans.

“Our research found significant reductions in preterm birth and severe asthma attacks in childhood, as well as a 5% decline in children being born very small for gestational age after the introduction of smoke-free laws”, says Dr Been.

“Together with the known health benefits in adults, our study provides clear evidence that smoking bans have considerable public health benefits for perinatal and child health, and provides strong support for WHO recommendations to create smoke-free public environments on a national level.”*

“This research has demonstrated the very considerable potential that smoke-free legislation offers to reduce preterm births and childhood asthma attacks,” says study co-author Professor Aziz Sheikh, of Brigham and Women’s Hospital, USA, and the University of Edinburgh, UK. “The many countries that are yet to enforce smoke-free legislation should in the light of these findings reconsider their positions on this important health policy question.”*

Writing in a linked Comment, Sara Kalkhoran and Stanton Glantz from the University of California San Francisco in the USA point out that, “Medical expenses for asthma exceeded US$50 billion in the USA in 2007, and US$20 billion in Europe in 2006. If asthma emergency department visits and admissions to hospital decreased by even 10%, the savings in the USA and Europe together would be US$7 billion annually.”

They conclude, “The cigarette companies, their allies, and the groups they sponsor have long used claims of economic harm, particularly to restaurants, bars, and casinos, to oppose smoke-free laws despite consistent evidence to the contrary. By contrast, the rapid economic benefits that smoke-free laws and other tobacco control policies bring in terms of reduced medical costs are real. Rarely can such a simple intervention improve health and reduce medical costs so swiftly and substantially.”