A law came into force in Scotland in December 2016 which made it illegal to smoke in a vehicle carrying anyone under 18.
Research led by the University of Glasgow, in collaboration with the universities of Aberdeen and Stirling, looked at data on all asthma emergency admissions to hospital in Scotland between 2000 and 2018 for children younger than 16.
The researchers found that after the smoke-free vehicle legislation was passed, asthma hospital admissions fell by 1.49% per month among pre-school children, though not in older children.
The study also shows hospital admissions fell significantly among children living in the most affluent areas (by 2.27% per month) but not in those living in the most deprived areas.
There was no change in admissions to hospital for other respiratory conditions or gastroenteritis following the legislation.
Professor Jill Pell, lead author from the University of Glasgow, said: “Our study demonstrates the significant benefit to children that smoke-free vehicle legislation has had.
“We found the reduction in asthma hospitalisations was specific to pre-school children, which is plausible given that exposure to parental smoke is more likely among pre-school children, who spend more time with parents.
“Our findings also suggested a possible widening of health inequalities whereby the relative reduction in childhood asthma hospitalisations was greater among those in the most affluent areas.
“This could be due to different starting points or differences in car ownership or compliance with the legislation; but merits further research. ”