Hospital Admission Trends for Bronchiolitis in Scotland, 2001–2016: A National Retrospective Observational Study
Authors: Chung Alexandria , Reeves Rachel M , Nair Harish , Campbell Harry ,   RESCEU investigators, Reeves Rachel M , Li You , Campbell Harry , Nair Harish , van Wijhe Maarten , Fischer Thea Kølsen , Simonsen Lone , Trebbien Ramona , Tong Sabine , Bangert Mathieu , Demont Clarisse , Lehtonen Toni , Heikkinen Terho , Teirlinck Anne , van Boven Michiel , van der Hoek Wim , van der Maas Nicoline , Meijer Adam , Fernandez Liliana Vazquez , Bøas Håkon , Bekkevold Terese , Flem Elmira , Stona Luca , Speltra Irene , Giaquinto Carlo , Cheret Arnaud , Leach Amanda , Stoszek Sonia , Beutels Philippe , Bont Louis , Pollard Andrew , Openshaw Peter , Abram Michael , Swanson Kena , Rosen Brian , Molero Eva , Reeves Rachel M , Li You , Campbell Harry , Nair Harish , van Wijhe Maarten , Fischer Thea Kølsen , Simonsen Lone , Trebbien Ramona , Tong Sabine , Bangert Mathieu , Demont Clarisse , Lehtonen Toni , Heikkinen Terho , Teirlinck Anne , van Boven Michiel , van der Hoek Wim , van der Maas Nicoline , Meijer Adam , Fernandez Liliana Vazquez , Bøas Håkon , Bekkevold Terese , Flem Elmira , Stona Luca , Speltra Irene , Giaquinto Carlo , Cheret Arnaud , Leach Amanda , Stoszek Sonia , Beutels Philippe , Bont Louis , Pollard Andrew , Openshaw Peter , Abram Michael , Swanson Kena , Rosen Brian , Molero Eva 
Published: June 2020

Abstract

Background
Bronchiolitis is the commonest cause of respiratory related hospital admissions in young children. This study aimed to describe temporal trends in bronchiolitis admissions for children under 2 years of age in Scotland by patient characteristics, socioeconomic deprivation, and duration of admission.

Methods
The national hospital admissions database for Scotland was used to extract data on all bronchiolitis admissions (International Classification of Disease, Tenth Revision, code J21) in children &lt;2 years of age from 2001 to 2016. Deprivation quintiles were classified using the 2011 Scottish Index of Multiple Deprivation.

Results
Over the 15-year study period, admission rates for children under 2 years old increased 2.20-fold (95% confidence interval [CI], 1.4–3.6-fold) from 17.2 (15.9–18.5) to 37.7 (37.4–38.1) admissions per 1000 children per year. Admissions peaked in infants aged 1 month, and in those born in the 3 months preceding the peak bronchiolitis month—September, October, and November. Admissions from the most-deprived quintile had the highest overall rate of admission, at 40.5 per 1000 children per year (95% CI, 39.5–41.5) compared with the least-deprived quintile, at 23.0 admissions per 1000 children per year (22.1–23.9). The most-deprived quintile had the greatest increase in admissions over time, whereas the least-deprived quintile had the lowest increase. Zero-day admissions, defined as admission and discharge within the same calendar date, increased 5.3-fold (5.1–5.5) over the study period, with the highest increase in patients in the most-deprived quintile.

Conclusions
This study provides baseline epidemiological data to aid policy makers in the strategic planning of preventative interventions. With the majority of bronchiolitis caused by respiratory syncytial virus (RSV), and several RSV vaccines and monoclonal antibodies currently in clinical trials, understanding national trends in bronchiolitis admissions is an important proxy for determining potential RSV vaccination strategies.