Temporal Trends, In-hospital Outcomes and Comorbidity Profile in US Asthma Hospitalizations Between 2004 and 2017

Background: Asthma is a prevalent chronic respiratory condition and a common cause for admissions, but contemporary US data on hospitalization rates, comorbidity burden, and outcomes among patients admitted with asthma are limited.

Objectives: To examine annual trends of US asthma hospitalizations, comorbidity profile by patient factors, and in-hospital outcomes over 14 years (2004-2017).

Methods: Population based study using data from the US Nationwide Inpatient Sample (NIS). NIS, sponsored by the Agency for Healthcare Research and Quality (AHRQ), is the largest available all-payer data on inpatient stays from all US states participating in the Healthcare Cost and Utilization Project, covering >97% of the US population. We included hospitalizations with a primary diagnosis of asthma between 2004 and 2017. Outcomes were the number of hospitalizations per 100,000 population, length of stay, in-hospital ventilation, and costs. Annual changes in patient and admission characteristics were examined. Multivariable regression models were used to identify predictors of in-hospital outcomes over-time. All analyses were survey-weighted to produce a nationally representative estimate of the entire US population of hospitalized patients.

Results: A total of 3,098,863 (996/100,000 population) asthma hospitalizations were identified between 2004 and 2017. Hospitalizations declined from 89/100,000 in 2004 to 56/100,000 population in 2017, mean (±SD) length of stay remained overall stable (2.71±2.5 days), but median (IQR) inflation-adjusted costs doubled from $8,444 (9,225) in 2004 to $17,756 (19,434) in 2017. Mean age was 29 (±25) years, 36% White, 27% Black, 57% females, and 40% by Medicaid payer. Common comorbidities in adults were hypertension and diabetes; and in children, obesity, gastroesophageal reflux disease (GERD), anaemia. Mental illness prevalence increased by >50% over time. Psychoses (IRR, 1.10; 1.05-1.14; P< 0.001) and severe asthma (IRR, 95%CI, 2.48; 2.27-2.72; P< 0.001) were associated with 1-day longer stays. In comparison to White patients, Asian/Pacific Islanders were more likely to be intubated (OR: 2.35; 1.73-3.20; P< 0.001).

Conclusions: Declining US asthma hospitalizations may reflect improvements in community care. Our findings highlight increasing comorbidity burden and the changing landscape of asthma admissions may inform services redesign to support pre-hospitalization care.