Is there a relationship between opiate misuse and poor asthma control?

Problem

Opiate misusers are encouraged to smoke rather than inject drugs, in order to reduce the risk of overdose and blood borne virus transmission. Inhalation of opiates may trigger acute severe asthma and a secondary care clinic has demonstrated more rapidly progressive lung disease and premature death due to respiratory causes in heroin users. Furthermore, cigarette smoking and poly-drug use is the norm within this group of vulnerable adults, with inhalation of crack cocaine and cannabis also known to cause lung damage. Poorly controlled asthma is an independent risk factor for chronic obstructive pulmonary disease (COPD). A 2014 National UK report identified substance misuse in 6% of all asthma deaths. Furthermore, a lack of engagement with primary care services and an over reliance on emergency departments were common within this patient group. In addition, there was evidence of excessive prescribing of short-acting beta agonist (SABA) reliever inhalers, defined by over 12 inhalers prescribed in the previous 12 months, and under-prescribing of inhaled corticosteroid (ICS) preventer inhalers, defined by less than 12 inhalers prescribed in the previous 12 months.

Approach

The aim of the study was to assess whether opiate misuse is a risk factor for poorly controlled asthma when controlling for age, gender and smoking status. A retrospective (12 months) cohort primary care population study was undertaken, using Academic Health Science Networks sponsored access to a large anonymised general practice database (ReseaerchOne). A rigorous process to assemble the appropriate read codes required to extract the data was undertaken. The primary Outcome measure was the number of SABA inhalers prescribed in the previous 12 months, with poor asthma control defined by prescription of over 12 SABA inhalers. Secondary outcome measures included: the number of ICS inhalers prescribed; prescription of Long Acting Beta Agonist (LABA) monotherapy; asthma review attendance; flu vaccination rates; exclusion rates from the Quality and Outcomes Framework (QOF); diagnosis of COPD; and the number of oral steroids prescribed.

Findings

Data extraction and analysis are ongoing.

Consequences

There is a paucity of research to date, focusing on the respiratory health of substance misusers. The average age of death of a male heroin user is 43 years and respiratory health is emerging as one of the earlier onset long term conditions. Findings will complement our previously reported feasibility study examining screening for respiratory disorders in a substance misuse clinic and together will inform the development of a feasibility study for the provision of asthma care within pharmacy settings.