To assess whether the implementation of English smoke-free legislation in July 2007 was associated with a reduction in hospital admissions for childhood asthma.
Interrupted time series study using Hospital Episodes Statistics data from April 2002 to November 2010. Sample consisted of all children (aged ≤14 years) having an emergency hospital admission with a principle diagnosis of asthma.
Before the implementation of the legislation, the admission rate for childhood asthma was increasing by 2.2% per year (adjusted rate ratio 1.02; 95% confidence interval [CI]: 1.02–1.03). After implementation of the legislation, there was a significant immediate change in the admission rate of −8.9% (adjusted rate ratio 0.91; 95% CI: 0.89–0.93) and change in time trend of −3.4% per year (adjusted rate ratio 0.97; 95% CI: 0.96–0.98). This change was equivalent to 6802 fewer hospital admissions in the first 3 years after implementation. There were similar reductions in asthma admission rates among children from different age, gender, and socioeconomic status groups and among those residing in urban and rural locations.
These findings confirm those from a small number of previous studies suggesting that the well-documented population health benefits of comprehensive smoke-free legislation appear to extend to reducing hospital admissions for childhood asthma.
Comments
Smoke-free legislation results in better neonatal lung function what leads to less wheezing illnesses and asthma in early childhood.
We read with interest the publication by Millett et al. regarding the association between smoke-free legislation and reduced hospital admissions for childhood asthma. The decline in asthma admissions was suggested to be caused by reductions in second hand smoke exposure in the home and in this way less harmful direct exposure of smoke to the lungs. We present another explanation on how smoke-free legislation could result in less asthma.
In the WHISTLER birth cohort lung function was measured in healthy infants between December 2001 and December 2010. This time span covered three consecutive periods with increasing levels of smoke restriction. The Tobacco Law came into effect in 1990 and prohibited smoking in public premises. In 2004 it was extended to cover workplaces and public transport and in 2008 smoke-free legislation for bars and restaurants was implemented. We studied the effect of prenatal environmental tobacco smoke exposure on neonatal lung function and the effect of incremental smoke- free legislation in the Netherlands on smoke exposure during pregnancy and newborn lung function.
1748 infants were included. The percentage of smoke exposed pregnant women declined from 24.8% between 2001-2004 to 5% between 2008-2010 (p<0.001). Active maternal smoking during pregnancy non-significantly declined from 8.4% to 5.3% (p= 0.089). The effect of smoke exposure on neonatal lung function (compliance and resistance of the respiratory system (Crs/ Rrs)) was studied. Crs and Rrs were adjusted for age, length, weight and sex, since these are determinants of lung function. A higher compliance and lower resistance mean a better lung function. By using linear regression, smoke exposure in pregnancy was associated with 3 ml/kPa decrease in Crs and 0.7 kPa/l/s increase in Rrs after adjustment for active maternal smoking during pregnancy and other potential confounders. After adjustment for potential confounders median Crs increased in the three consecutive time periods (41.9 to 46.7 ml/kPa, p <0.001) and median Rrs decreased (7.1 to 5.9 kPa/l/s, p<0.001). Further adjustment of Crs and Rrs for active maternal smoking did not change the results.
Recently, in the same WHISTLER birth cohort study, we showed that reduced neonatal lung function was related to significantly more consultations for wheezing illnesses in the first five years of life, asthma diagnosis and lower FEV1 and FEF25-75 at the age of five (1).
We therefore conclude that the association between smoke-free legislation and hospital admissions for childhood asthma could not only be explained by a direct effect of smoke exposure on asthma, but also by reducing the number of pregnant women exposed to environmental tobacco smoke, resulting in better neonatal lung function, what leads to less wheezing illnesses and asthma in early childhood.
1. van der Gugten AC, Uiterwaal CS, van Putte-Katier N, Koopman M, Verheij TJ, van der Ent CK. Reduced neonatal lung function and wheezing illnesses during the first five years of life. Eur Respir J. 2012 Nov 8. [Epub ahead of print]
Conflict of Interest:
None declared