Rationale: The epidemiology of cigarette smoking-related chronic obstructive pulmonary disease (COPD) is not well characterized in Hispanics in the United States. Understanding how ethnicity influences COPD is important for a number of reasons, from informing public health policies to dissecting the genetic and environmental effects that contribute to disease.
Objectives: The present study assessed differences in risk between Hispanics and non-Hispanic whites for longitudinal and cross-sectional COPD phenotypes. Genetic ancestry was used to verify findings based on self-reported ethnicity. Hispanics in New Mexico are primarily differentiated from non-Hispanic whites by their proportion of Native American ancestry.
Methods: The study was performed in a New Mexican cohort of current and former smokers. Self-reported Hispanic and non-Hispanic white ethnicity was validated by defining genetic ancestry proportions at the individual level using 48 single-nucleotide polymorphism markers. Self-reported ethnicity and genetic ancestry were independently used to assess associations with cross-sectional and longitudinal measures of lung function. Multivariable models were adjusted for indicators of smoking behavior.
Measurements and main results: Self-reported Hispanic ethnicity was significantly associated with lower odds of COPD (odds ratio, 0.49; 95% confidence interval, 0.35-0.71; P = 0.007), and this protection was validated by the observation that Hispanic smokers have reduced risk of rapid decline in lung function (odds ratio, 0.48; 95% confidence interval, 0.30-0.78; P = 0.003). Similar findings were noted when Native American genetic ancestry proportions were used as predictors instead of self-report of Hispanic ethnicity.
Conclusions: Hispanic ethnicity is inversely associated with cross-sectional and longitudinal spirometric COPD phenotypes even after adjustment for smoking. Native American genetic ancestry may account for this "Hispanic protection."