Prevalence of chronic obstructive pulmonary disease in Greater Glasgow and Clyde: impact of smoking on socioeconomic and sex inequalities

Abstract Background In high-income countries, socioeconomic and sex inequalities in chronic obstructive pulmonary disease (COPD) have been largely linked to smoking. We aimed to assess the effect of smoking status on socioeconomic and sex inequalities in COPD prevalence in Greater Glasgow and Clyde. Methods COPD and smoking status collected by the Quality and Outcomes Framework until Oct 31, 2016, were linked to mortality data. Population estimates for smoking status by age, sex, and Scottish Index of Multiple Deprivation (SIMD) for Greater Glasgow and Clyde were calculated using 2013, 2014, and 2015 Scottish Household Survey datasets. COPD prevalence by sex, age group (10-year age bands), and socioeconomic status was compared before and after adjustment for smoking status. Findings COPD prevalence was higher for men than women at younger and oldest ages. But for the 45–54, 55–64, and 65–74-year age groups, prevalence among women was 1·9% (n=1652), 5·8% (n=4289), and 10·1% (n=5513), respectively, versus 1·7% (n=1331), 4·7% (n=3203), and 9·8% (n=4708) for men. Prevalence of current smoking was higher among younger than older age groups, particularly among women; 24·6% (95% CI 21·8–27·5) of women aged 16–34 years currently smoked versus 10·9% (8·2–13·6) aged 75 years or older. Prevalence of ever smoking, for individuals aged 85 years or older, however, was 87·1% (78·5–95·6) in men versus 41·7% (33·2–50·3) in women. Prevalence of COPD, current smoking, and ever smoking in SIMD1 (most deprived) was, respectively, 3·5 (3·4–3·6), 4·5 (4·0–5·3), and 1·7 (1·7–1·8) times that in SIMD5 (least deprived). After adjustment for age and sex, socioeconomic inequalities in COPD increased, with SIMD1 prevalence 4·8 (4·7–5·0) times that of SIMD5. After adjustment for age, sex, and current (or ever) smoking, SIMD1 prevalence was 2·5 (2·4–2·5) (or 3·1 [3·0–3·2]) times that of SIMD5. After adjustment for age and SIMD, COPD prevalence in men was 1·2 (1·2–1·2) times that in women. Adjustment for ever smoking reversed inequalities; male prevalence was 0·9 (0·9–0·9) times that of female prevalence. Interpretation Smoking accounts for around half the gap in prevalence of COPD between the most and least deprived groups, whereas sex inequalities are reversed after adjustment for smoking status. Factors other than smoking must be considered to tackle socioeconomic and sex inequalities in COPD. Funding Glasgow City Council provided financial support for the preparation of the abstract. The funder had no role in data analysis or interpretation, writing of the abstract, or the decision to submit for publication.