# Risk Factors for Severe Bronchiolitis in Australian and Aotearoa New Zealand Infants: A Systematic Review

## TL;DR

This study reviews risk factors for severe bronchiolitis in infants from Australia and New Zealand, identifying factors like prematurity and comorbidities that increase hospitalization risk.

## Contribution

The study provides a systematic review of risk factors specific to Australasian infants with bronchiolitis, highlighting gaps in evidence compared to international findings.

## Key findings

- Younger age, prematurity, and comorbidities are significant risk factors for severe bronchiolitis.
- Evidence for breastfeeding and faltering growth as risk factors is lacking in the Australasian context.
- Some risk factors like trisomy-21 are not reported in Australasian infants.

## Abstract

Bronchiolitis is the leading cause of hospital admission in Australasian infants. Infants with risk factors for severe disease may have a greater likelihood of prolonged hospitalisation and intensive care admission. This study aimed to synthesise the literature on risk factors for severe bronchiolitis in Australasian infants.

Systematic review including observational studies of risk factors for severe bronchiolitis in Australasian infants (< 12 months), published from 2000. Databases were searched (24 January 2024): MEDLINE, EMBASE, PubMed, Cochrane Library and CINAHL. Risk of bias (RoB) was assessed using the Newcastle–Ottawa Scale for cohort studies, and evidence quality was evaluated using GRADE. Results were narratively synthesised.

Ten out of 26 467 articles were included (N = 895 276; 12 cohorts, prospective = 5, retrospective = 7). Studies were mostly rated low RoB. There was evidence for the following risk factors: younger chronological age, prematurity, plural birth, comorbidity (chronic lung disease, congenital heart disease, chronic neurological disease, any genetic disorder, any comorbidity), Indigenous ethnicity, economic disadvantage, tobacco smoke exposure and timing of illness onset at presentation. Most risk factors had moderate‐quality evidence (range high to very low). Evidence was lacking for the following risk factors present in international literature: breastfeeding exposure and faltering growth. The following risk factors have not been reported in Australasian infants: trisomy‐21, congenital diaphragmatic hernia and environmental pollutants.

Risk factors for severe bronchiolitis in Australasian infants are largely consistent with the international literature, although evidence is lacking for some. Knowledge of these risk factors is highly relevant to those assessing infants with bronchiolitis, and in guiding targeted delivery of respiratory syncytial virus immunisation and other preventative programmes.

PROSPERO (CRD42023463917)