EPHX1 and chronic obstructive pulmonary disease: In the analyses stratified by ethnicity, the increased COPD risk of extremely slow and slow EPHX1 enzyme activity was observed in the Caucasian populations (extremely slow enzyme activity: OR, 2.64; 95% CI, 1.30–5.38; slow enzyme activity: OR, 1.31; 95% CI, 1.01–1.71), but not in the Asian populations (extremely slow enzyme activity: OR, 0.1.14; 95% CI, 0.84–1.54; slow enzyme activity: OR, 1.41; 95% CI, 0.90–2.19).