Cigarettes per day and ethnicity in London

Abstract

Background: Black people in London are at significantly lower risk of COPD than white people (OR 0.44; 0.39 to 0.51) when age, smoking, sex and deprivation are accounted for, but disease seems no less severe. Genetic factors in the metabolism and addictive potential of nicotine have been considered in these differences. The role of number of cigarettes smoked per day (CPD), not previously investigated, is assessed here. Methods: This retrospective cross-sectional study used routinely-collected primary care data. CPD (most recent value) was compared between ethnic groups using linear regression, adjusting for age, sex and deprivation, to produce adjusted mean CPD. Results: 358,614 patients were included. 67.3% of current smokers (44,146) and 20.3% of ex-smokers (13,700) had CPD recorded. Overall, mean CPD was 9.6 (SD 7.7), and median CPD 10 (IQR 4-15). In the white group (n=33,385), adjusted mean CPD was 10.5 (95% CI 10.4-10.6) and median CPD 10 (IQR 5-15). In the black group (n=9533), adjusted mean CPD was 7.3 (95% CI 7.2-7.5) and median CPD 5 (IQR 3-10). In the Asian group (n=2254), adjusted mean CPD was 7.9 (95% CI 7.6-8.2) and median CPD 6 (IQR 3-10). Adjusted mean CPD was significantly lower in the black (B=-3.2, -3.3 to -3.0) and Asian (B=-2.6, -2.9 to -2.3) groups compared to the white group. Discussion: Black smokers in London smoke significantly fewer cigarettes than white smokers. This finding may explain some of the difference between ethnic groups in the observed prevalences of COPD. Differences in CPD may be due to cultural, social and reporting factors, but these findings may also reflect important differences in the genetic factors that determine the delivery and sensitivity to nicotine and its addictive potential.