Management of People with Asthma in Primary Care by Smoking Status: A Cohort Study

Background Previous studies suggest that cigarette smokers with chronic respiratory disease may be managed differently. However, evidence is limited on whether smoking status impacts asthma management. Methods Data from the UK Clinical Practice Research Datalink (CPRD) Aurum were used to define a cohort of adults (aged over 18) diagnosed with asthma between January 1, 2010, and March 31, 2021. Start of follow-up was defined at first recorded asthma diagnosis. End of follow-up was March 31, 2021, or earlier if patients died or left the general practice. The exposure was the most recently recorded cigarette smoking status prior to asthma diagnosis, categorised as never, ex, or current smokers. Two outcome measures were used to assess asthma management: i) a record of at least one inhaled corticosteroid (ICS) prescription in the first year of follow-up and ii) asthma annual review visits over the follow-up period. Logistic and negative binomial regression models were applied, respectively, adjusting for potential confounders. An interaction with sex was tested to account for differences in asthma management in males and females. Results Among 241,624 adults with asthma (59.6% female, mean age 50.8), current smokers were less likely to receive ICS than never smokers (OR 0.94, 95% CI 0.91–0.96), while ex-smokers were more likely (OR 1.09, 95% CI 1.07–1.11). A sex interaction showed males were less likely to receive ICS than females among never smokers. Current smokers also had lower annual review rates (IRR 0.83, 95% CI 0.82–0.84), whereas ex-smokers had rates similar to never smokers (IRR 0.99, 95% CI 0.98–1.00). Males had lower review rates than females among never smokers only. Conclusion Cigarette smoking status influences asthma management. Findings highlight the importance of considering smoking status in planning and tailoring asthma care.