Does COPD risk vary by ethnicity? A retrospective cross-sectional study

BACKGROUND: Lower risk of COPD has been reported in black and Asian people, raising questions of poorer recognition or reduced susceptibility. We assessed prevalence and severity of COPD in ethnic groups, controlling for smoking. METHOD: A retrospective cross-sectional study using routinely collected primary care data in London. COPD prevalence, severity (% predicted forced expiratory volume in 1 second FEV1), smoking status, and treatment were compared between ethnic groups, adjusting for age, sex, smoking, deprivation, and practice clustering. RESULTS: Among 358,614 patients in 47 general practices, 47.6% were white, 20% black, and 5% Asian. Prevalence of COPD was 1.01% overall, 1.55% in whites, 0.58% in blacks, and 0.78% in Asians. COPD was less likely in blacks (adjusted odds ratio OR, 0.44; 95% confidence interval CI 0.39-0.51) and Asians (0.82; CI, 0.68-0.98) than whites. Black COPD patients were less likely to be current smokers (OR, 0.56; CI, 0.44-0.71) and more likely to be never-smokers (OR, 4.9; CI, 3.4-7.1). Treatment of patients with similar disease severity was similar irrespective of ethnic origin, except that long-acting muscarinic antagonists were prescribed less in black COPD patients (OR, 0.53; CI, 0.42-0.68). Black ethnicity was a predictor of poorer lung function (% predicted FEV1: B coefficient, -7.6; P<0.0001), an effect not seen when ethnic-specific predicted FEV1 values were used. CONCLUSION: Black people in London were half as likely as whites to have COPD after adjusting for lower smoking rates in blacks. It seems likely that the differences observed were due either to ethnic differences in the way cigarettes were smoked or to ethnic differences in susceptibility to COPD.