The number of children admitted to hospital with symptoms of asthma has fallen since the ban on smoking in enclosed public places came into effect, a study has found.
Research shows there was a 12.3% fall in admissions in the first year after the law was introduced in July 2007, and these have continued to drop in subsequent years, suggesting that any benefits of the legislation have been sustained.
NHS statistics analysed by researchers at Imperial College London showed the decline was equivalent to 6,802 fewer hospital admissions in the first three years of the law coming into effect.
The findings have been published in the journal Pediatrics. Asthma affects one in 11 children in the UK.
Before the ban was implemented, hospital admissions for children suffering a severe asthma attack were increasing by 2.2% a year, peaking at 26,969 admissions in 2006-07.
The findings show the trend reversed immediately after the law came into effect, with lower admission rates among boys and girls of all ages, in both wealthy and poor neighbourhoods and in cities and rural areas.
Previous studies have shown that hospital admissions for childhood asthma fell after smoke-free legislation was introduced in Scotland and North America. The smoking ban in England has also been found to have reduced the rate of heart attacks.
Dr Christopher Millett, from Imperial College London's School of Public Health, who led the study said: "There is already evidence that eliminating smoking from public places has resulted in substantial population health benefits in England, and this study shows that those benefits extend to reducing hospital admissions for childhood asthma.
"Previous studies have also suggested that the smoke-free law changed people's attitudes about exposing others to secondhand smoke and led more people to abstain from smoking voluntarily at home and in cars. We think that exposing children to less secondhand smoke in these settings probably played an important role in reducing asthma attacks.
"The findings are good news for England, and they should encourage countries where public smoking is permitted to consider introducing similar legislation."
Emily Humphreys, head of policy and public affairs at Asthma UK, said the findings were encouraging. She said: "It's great to see growing evidence of the positive impact of smoke-free legislation. This is something we campaigned for, so it is particularly encouraging that there has been a fall in children's hospital admissions for asthma since its introduction.
"We have long known that smoking and secondhand smoke are harmful – they not only trigger asthma attacks which put children in hospital but can even cause them to develop the condition. We've seen the benefits of reducing secondhand smoke exposure; now we need to do more to prevent children and young people from taking up smoking by introducing plain packaging for tobacco."