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Smoke-free legislation and paediatric hospitalisations for acute respiratory tract infections: national quasi-experimental study with unexpected findings and important methodological implications

Been, Jasper V.; Mackay, Daniel F.; Millett, Christopher; Soyiri, Ireneous; van Schayck, Constant P.; Pell, Jill P.; Sheikh, Aziz

Authors

Jasper V. Been

Daniel F. Mackay

Christopher Millett

Constant P. van Schayck

Jill P. Pell

Aziz Sheikh



Abstract

Objectives We investigated whether Scottish implementation of smoke-free legislation was associated with a reduction in unplanned hospitalisations or deaths (‘events’) due to respiratory tract infections (RTIs) among children.

Design Interrupted time series (ITS).

Setting/participants Children aged 0–12 years living in Scotland during 1996–2012.

Intervention National comprehensive smoke-free legislation (March 2006).

Main outcome measure Acute RTI events in the Scottish Morbidity Record-01 and/or National Records of Scotland Death Records.

Results 135 134 RTI events were observed over 155 million patient-months. In our prespecified negative binomial regression model accounting for underlying temporal trends, seasonality, sex, age group, region, urbanisation level, socioeconomic status and seven-valent pneumococcal vaccination status, smoke-free legislation was associated with an immediate rise in RTI events (incidence rate ratio (IRR)=1.24, 95% CI 1.20 to 1.28) and an additional gradual increase (IRR=1.05/year, 95% CI 1.05 to 1.06). Given this unanticipated finding, we conducted a number of post hoc exploratory analyses. Among these, automatic break point detection indicated that the rise in RTI events actually preceded the smoke-free law by 16 months. When accounting for this break point, smoke-free legislation was associated with a gradual decrease in acute RTI events: IRR=0.91/year, 95% CI 0.87 to 0.96.

Conclusions Our prespecified ITS approach suggested that implementation of smoke-free legislation in Scotland was associated with an increase in paediatric RTI events. We were concerned that this result, which contradicted published evidence, was spurious. The association was indeed reversed when accounting for an unanticipated antecedent break point in the temporal trend, suggesting that the legislation may in fact be protective. ITS analyses should be subjected to comprehensive robustness checks to assess consistency.

Journal Article Type Article
Publication Date 2018-10
Journal Tobacco Control
Print ISSN 0964-4563
Electronic ISSN 1468-3318
Publisher BMJ Publishing Group
Peer Reviewed Peer Reviewed
Volume 27
Issue e2
Pages e160-e166
APA6 Citation Been, J. V., Mackay, D. F., Millett, C., Soyiri, I., van Schayck, C. P., Pell, J. P., & Sheikh, A. (2018). Smoke-free legislation and paediatric hospitalisations for acute respiratory tract infections: national quasi-experimental study with unexpected findings and important methodological implications. Tobacco Control, 27(e2), e160-e166. https://doi.org/10.1136/tobaccocontrol-2017-053801
DOI https://doi.org/10.1136/tobaccocontrol-2017-053801
Publisher URL https://tobaccocontrol.bmj.com/content/27/e2/e160
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