Impact of body mass index on outcomes of non-cystic fibrosis bronchiectasis

BACKGROUND: Low body mass index (BMI) is associated with poor prognosis in patients with non-cystic fibrosis (non-CF) bronchiectasis. However, the impact of being overweight or obese on clinical outcomes of these patients remains controversial. MATERIALS AND METHODS: This retrospective cohort study was conducted using TriNetX. Patients diagnosed with non-CF bronchiectasis between 2012 and 2022 were identified. The eligible population was divided into four groups based on their BM. Propensity score matching (PSM) was used to balance baseline demographic and clinical characteristics between study groups. The primary outcome of interest was all-cause mortality during a 5-year follow-up period. RESULTS: A total of 14 469 patients were included in the analysis. After PSM, the underweight group exhibited significantly higher all-cause mortality compared with those with a normal BMI (24.3% vs 15.3%; HR 1.83; 95% CI 1.49 to 2.25; p=0.0150). Conversely, both the overweight (16.6% vs 21.4%; HR 0.77; 95% CI 0.68 to 0.88; p=0.0138) and obese groups (16.8% vs 20.2%; HR 0.79; 95% CI 0.71 to 0.87; p=0.0356) demonstrated lower all-cause mortality rates. In addition, consistently higher risks in the underweight group and lower risks in the overweight and obese groups were observed for several critical health outcomes, including the need for critical care service, incidence of pneumonia, tuberculosis or non-tuberculous mycobacterial infection, acute exacerbation of bronchiectasis, acute respiratory failure and ventilator use. CONCLUSIONS: Being underweight is a risk factor for all-cause mortality in patients with non-CF bronchiectasis and the aforementioned clinical outcomes. Conversely, overweight and obesity are associated with lower all-cause mortality rates and better outcomes.