Rural Residence and COPD Exacerbations: Analysis of the SPIROMICS Cohort.

RATIONALE: Rural residence is associated with poor outcomes in several chronic diseases. The association between rural residence and chronic obstructive pulmonary disease (COPD) exacerbations remains unclear.

OBJECTIVE: To determine the independent association between rural residence and COPD-related outcomes including COPD exacerbations, airflow obstruction and symptom burden.

METHODS: A total of 1684 Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) participants with FEV1/FVC<0.70 had geocoding-defined rural-urban residence status determined (N=204 rural and N=1480 urban). Univariate and multivariate logistic and negative binomial regressions were performed to assess the independent association between rurality and COPD outcomes including exacerbations, lung function, and symptom burden. The primary exposure of interest was rural residence, determined by geocoding of home address to the block level at time of study enrollment. Additional covariates of interest included demographic and clinical characteristics, occupation, and occupational exposures.The primary outcome measures were exacerbations determined over the one-year course after enrollment by quarterly telephone calls and at an annual research clinic visit. Odds ratio and incidence rate of exacerbations that required treatment with medications including steroids or antibiotics (total exacerbations), and exacerbations leading to hospitalization (severe exacerbations) were determined after adjusting for relevant covariates.

RESULTS: Rural residence was independently associated with 70% increase in odds of total exacerbations [OR 1.70 (95% CI 1.13-2.56); p=0.012] and 46% higher incidence rate of total exacerbations [IRR 1.46 (95% CI 1.02-2.10); p=0.039]. There was no association between rural residence and severe exacerbations. Agricultural occupation was independently associated with increased odds and incidence of total and severe exacerbations. Inclusion of agricultural occupation to analysis attenuated the association between rural residence and odds and incidence rate of total exacerbations [OR 1.52 (95% CI 1.00-2.32; p=0.05) and IRR 1.39 (95% CI 0.97 - 1.99); p=0.07]. There was no difference in symptoms or airflow obstruction between rural and urban participants.

CONCLUSIONS: Rural residence is independently associated with increased odds and incidence of total, but not severe COPD exacerbations. These associations are not fully explained by agriculture-related exposures, highlighting the need for future research into potential mechanisms of increased risk of COPD exacerbations in the rural population.