Prevalence of common chronic respiratory diseases in drug misusers: a cohort study

Background: A randomised controlled trial of substance misuse indicated that many patients who use methadone have respiratory symptoms and/or are prescribed respiratory medications. There is little research in this area. 

Aims: To determine the prevalence of respiratory disease and prescriptions among drug misusers. 

Methods: This historical cohort study of drug misusers and matched controls analysed routinely collected primary care data. The prevalence of common chronic respiratory diseases, class and number of respiratory medications were examined. Results: The cohort of 18,570 patients (9,285 per group) was mostly male (64%, n=11,890) and aged 31-59 years (76%, n=14,060). After adjusting for age, gender, deprivation and smoking status, the results showed that more drug misusers than controls had a diagnosis of asthma or chronic obstructive pulmonary disease (17.1% vs. 10.9%; adjusted odds ratio (OR) 1.61, 95% confidence interval (CI) 1.46 to 1.77, and 2.4% vs. 0.8%; OR 1.86, 95% CI 1.42 to 2.44, respectively) and were prescribed more chronic respiratory medications: short-acting β₂-agonists (16.4% vs. 7.9%; OR 2.00, 95% CI 1.80 to 2.22), long-acting β₂-agonists (1% vs. 0.4%; OR 1.93, 95% CI 1.29 to 2.89), and inhaled corticosteroids (10.6% vs. 7.6%; OR 1.49, 95% CI 1.33 to 1.67). All differences were statistically significant (p<0.001). 

Conclusions: Drug misusers have a significantly higher prevalence of respiratory diseases and respiratory prescriptions than matched controls. Further work is needed to determine the reasons for this.