The Protective Effect of Hispanic Ethnicity on Chronic Obstructive Pulmonary Disease Mortality is Mitigated by Smoking Behavior.

Abstract

Rationale: Studies in Hispanic/Latino populations have shown ethnicity to be either a predictive or protective factor for COPD mortality and it is unclear whether this disagreement is attributable to ethnic differences in smoking rates, smoking behavior or differences in genetic susceptibility.

Objectives: This study will examine the role of smoking behavior as a means of explaining differences in risk for COPD mortality between Hispanics and non-Hispanic whites.

Methods: Participants were recruited into a cohort study from the San Luis Valley in Colorado beginning in the early 1980's and followed for mortality until 2012. COPD and cardiovascular disease are often comorbid conditions and account for the competing risk of CVD in the analysis of COPD mortality. Mortality searches were conducted regularly and all ICD codes were collected for mortality event. Primary and secondary causes of each event were assessed using appropriate codes.

Results: Hispanic current smokers did not differ from NHW current smokers in years smoked (p=0.6) but Hispanic former smokers accumulated more years smoked compared to NHW former smokers (22 vs. 20, p=0.047). Hispanic ethnicity was significantly protective for COPD mortality adjusting for age, gender, pre-existing emphysema, hypertension and smoking status and accounting for the effect of CVD mortality (RR=0.58, 95% C.I. 0.34-0.99, p=0.035). Further adjustment for smoking behavior mitigated this effect.

Conclusions: The lower COPD mortality seen in Hispanic smokers may be due lower cumulative exposure to tobacco smoke. Thus, smoking behavior may play a key role in explaining differences in COPD mortality as they relate to Hispanic ethnicity.