Associations between smoke-free vehicle legislation and childhood admissions to hospital for asthma in Scotland: an interrupted time-series analysis of whole-population data

BACKGROUND
In Scotland, childhood asthma hospitalisations fell in March 2006 following legislation to prohibit smoking in public places. In December 2016, new Scottish legislation banned smoking in vehicles containing a child. This study aimed to determine if this produced additional benefit.

METHODS
Data were obtained on all asthma emergency hospitalisations in Scotland between 2000 and 2018 for individuals aged <16 years. Interrupted time series analyses studied changes in monthly incidence following the introduction of smoke-free vehicle legislation, taking account of previous smoke-free interventions. Sub-group analyses were undertaken by age and area-deprivation, and the analyses repeated for a control condition, gastroenteritis, and other respiratory conditions.
RESULTS
Of the 32,342 asthma hospitalisations, 13,954 related to children <5 years old. After the smoke-free vehicle legislation, the slope in asthma hospitalisations fell by 1.49% per month [95% CI 0.27 to 2.69]) relative to the underlying trend among children <5 years (equivalent to 6 fewer hospitalisations per annum), but not older children. Hospitalisations fell significantly among children living in the most affluent areas (2.27% per month [95% CI 0.07 to 4.41]) but not those living in the most deprived areas. There was no change in hospitalisations for gastroenteritis or other respiratory conditions following the legislation.
CONCLUSIONS
Legislation banning smoking in vehicles was associated with reduction in severe asthma attacks requiring hospitalisations among pre-school children, over and above the underlying trend and previous interventions designed to reduce exposure to second-hand smoke. Similar legislation should be adopted in other countries.