A primary care database study of asthma care and outcomes among patients with a history of opioid use disorder

Background Substance misuse is associated with poor asthma outcome and death. People with opioid use disorder (OUD) may be at particular risk, however, there have been no case-control studies of asthma care and outcomes in this patient group. Methods A primary care database study of patients with asthma aged 16-65 years was conducted using a matched case-control methodology. Cases with a lifetime history of OUD were matched to controls 1:3 by age, gender, smoking status and deprivation index decile. Outcomes were: attendance at asthma review, influenza vaccination, prescriptions for inhaled corticosteroids (ICS), courses of oral prednisolone, and concurrent diagnosis of COPD. Analysis was by conditional logistic regression. Results The dataset comprised 275,151 adults with asthma, of whom 459 had a clinical code indicating a lifetime history of OUD. Attendance at annual review (30%) and for immunisation (25%) was poor amongst the overall matched study population (N=1,832). Compared to matched controls, cases were less likely to have attended for asthma review during the previous 12-months (OR=0.60, 95% CI 0.45-0.80) but had similar immunisation rates. Higher rates of ICS (OR=1.50, 1.13-1.98) and oral prednisolone use (OR=1.71, 1.25-2.40) were seen amongst those with a history of OUD and 7.2% had a concurrent diagnosis of COPD (OR=1.86, 1.12-2.40). Conclusion This study is the first matched-case control study of care and outcome among patients with asthma and OUD and the first database study in this population. We found that people with asthma and a history of OUD have worse outcomes on several commonly measured metrics of asthma care. Further research is required to identify the most effective strategies to help this vulnerable group access basic asthma care, such as annual asthma review, and to better understand how OUD affects asthma over time.