Association of blood eosinophil counts with pulmonary and extrapulmonary comorbidities in patients with chronic obstructive pulmonary disease: data from NHANES 2013-2018.

Background: Chronic obstructive pulmonary disease (COPD) involves systemic inflammation and is often accompanied by comorbidities. Blood eosinophil count (BEC) is a key marker of airway inflammation, used for patient stratification and treatment guidance. However, the association between BEC (< 300 vs. ≥ 300 cells/µL) and pulmonary or extrapulmonary comorbidities in COPD remains unclear.

Methods: This study analyzed COPD patients from the 2013-2018 National Health and Nutrition Examination Survey (NHANES). Weighted multivariable logistic regression models examined associations between BEC and comorbidities, adjusting for potential confounders. Associations were quantified using odds ratios (ORs) and 95% confidence intervals (CIs).

Results: A total of 614 COPD patients were included (395 with BEC < 300 cells/µL, 219 with BEC ≥ 300 cells/µL). Patients with BEC ≥ 300 cells/µL had a higher prevalence of extrapulmonary comorbidities than those with BEC < 300 cells/µL (85.35% vs. 71.48%). Adjusted analysis showed that BEC ≥ 300 cells/µL was significantly associated with increased odds of any extrapulmonary comorbidity (OR = 2.03, 95% CI: 1.19-3.44, p = 0.009), congestive heart failure (OR = 1.69, 95% CI: 1.02-2.82, p = 0.043), and renal dysfunction (OR = 1.95, 95% CI: 1.01-3.79, p = 0.048), but not with pulmonary comorbidities. Sensitivity analyses using 3- and 4-level BEC categories revealed consistent trends, with higher BEC levels significantly associated with greater prevalence of at least one extrapulmonary comorbidity.

Conclusions: In COPD, higher BEC (≥ 300 cells/µL) is significantly associated with extrapulmonary comorbidities, particularly congestive heart failure and renal dysfunction, but not pulmonary comorbidities.