Obesity and New‐Onset Asthma Risk in Chronic Rhinosinusitis: A Population‐Based Cohort Study

ABSTRACT Objective Obesity and chronic rhinosinusitis (CRS) are independently associated with asthma, yet their combined impact on asthma risk remains less understood. This study evaluates the association between elevated body mass index (BMI) and new‐onset asthma and asthma exacerbations in patients with CRS. Methods A retrospective cohort study was conducted using the TriNetX U.S. Collaborative Network. Adults ≥ 18 years with unspecified CRS and recorded BMI from 2009 to 2019 were identified. Patients with prior functional endoscopic sinus surgery were excluded. Cohorts were stratified by BMI (healthy, overweight, obese) and matched 1:1 by demographics and comorbidities. Primary outcomes were adjusted relative risks (aRR) of new‐onset asthma and asthma exacerbations within 1, 2, and 5 years after BMI classification. A secondary analysis was performed in patients without CRS using the same BMI stratification and matching approach. Results Overweight CRS patients had a higher risk of new‐onset asthma (aRR = 1.13, 95% CI 1.10–1.17) and exacerbations (aRR = 1.24, 95% CI 1.18–1.30) at 1 year compared to healthy‐weight controls, with similar trends at 2 and 5 years. Obese CRS patients showed greater risks of new‐onset asthma (aRR = 1.44, 95% CI 1.40–1.48) and exacerbations (aRR = 1.71, 95% CI 1.63–1.79) at 1 year, persisting at 2 and 5 years. In secondary analyses, elevated BMI was associated with increased relative asthma risk in patients without CRS, though absolute rates remained higher among CRS patients. Conclusions Elevated BMI is associated with increased risk of asthma onset and exacerbations in CRS patients, with a graded relationship across BMI categories. Secondary analyses in patients without CRS suggest this association likely reflects the broader relationship between excess adiposity and asthma rather than a uniquely CRS‐specific effect; however, higher absolute asthma rates among CRS patients support the clinical relevance of BMI assessment in this population. Level of Evidence 4