Body mass index and in-hospital mortality in patients with acute exacerbation of idiopathic pulmonary fibrosis

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease characterised by chronic fibrosis, and acute exacerbation of IPF (AE-IPF) is the leading cause of death in patients with IPF. Data on the association between the body mass index (BMI) and prognosis of AE-IPF are lacking. This study was performed to evaluate the association between BMI and in-hospital mortality in patients who developed AE-IPF using a national inpatient database. METHODS: Using the Japanese Diagnosis Procedure Combination database, we retrospectively collected data of inpatients with AE-IPF from 1 July, 2010 to 31 March, 2018. We performed a multivariable logistic regression analysis to evaluate the association between all-cause in-hospital mortality and BMI, categorised as underweight (<18.5 kg·m(−2)), low-normal weight (18.5–22.9 kg·m(−2)), high-normal weight (23.0–24.9 kg·m(−2)), overweight (25.0–29.9 kg·m(−2)) and obese (≥30.0 kg·m(−2)). RESULTS: In total, 14 783 patients were eligible for this study. The in-hospital mortality rate was 59.0%, 55.0%, 53.8%, 54.8% and 46.0% in the underweight, low-normal weight, high-normal weight, overweight and obese groups, respectively. Underweight patients had a significantly higher mortality rate (OR 1.25, 95% CI 1.10–1.42) and obese patients had a significantly lower mortality rate (OR 0.71, 95% CI 0.54–0.94) than low-normal weight patients. CONCLUSION: Among patients with AE-IPF, the underweight group had higher mortality and the obese group had lower mortality.