Risk factors for asthma-related hospital and intensive care admissions in children, adolescents and adults: a cohort study using primary and secondary care data.

BACKGROUND: Asthma remains a common cause of hospital admissions across the life course. We estimated the contribution of key risk factors to asthma-related hospital and intensive care unit (ICU) admissions in children, adolescents and adults.

METHODS: This was a UK-based cohort study using linked primary care (Clinical Practice Research Datalink Aurum) and secondary care (Hospital Episode Statistics Admitted Patient Care) data. Patients were eligible if they were aged 5 years and older and had been diagnosed with asthma. This included 90 989 children aged 5-11 years, 114 927 adolescents aged 12-17 years and 1 179 410 adults aged 18 years or older. The primary outcome was asthma-related hospital admissions from 1 January 2017 to 31 December 2019. The secondary outcome was asthma-related ICU admissions. Incidence rate ratios adjusted for demographic and clinical risk factors were estimated using negative binomial models. Population attributable fraction (PAF) was estimated for modifiable risk factors.

RESULTS: Younger age groups, females and those from ethnic minority and lower socioeconomic backgrounds had an increased risk of asthma-related hospital admissions. Increasing medication burden, including excessive use of short-acting bronchodilators, was also strongly associated with the primary outcome. Similar risk factors were observed for asthma-related ICU admissions. The key potentially modifiable or treatable risk factors were smoking in adolescents and adults (PAF 6.8%, 95% CI 0.9% to 12.3% and 4.3%, 95% CI 3.0% to 5.7%, respectively), and obesity (PAF 23.3%, 95% CI 20.5% to 26.1%), depression (11.1%, 95% CI 9.1% to 13.1%), gastro-oesophageal reflux disease (2.3%, 95% CI 1.2% to 3.4%), anxiety (2.0%, 95% CI 0.5% to 3.6%) and chronic rhinosinusitis (0.8%, 95% CI 0.3% to 1.3%) in adults.

CONCLUSIONS: There are significant sociodemographic inequalities in the rates of asthma-related hospital and ICU admissions. Treating age-specific modifiable risk factors should be considered an integral part of asthma management, which could potentially reduce the rate of avoidable hospital admissions.