COPD and asthma in patients with opioid dependency: a cross-sectional study in primary care

S Mehta,C J Jolley,P White,S Durbaba,M Kelleher,M Ashworth,N Parmar

doi:10.1038/s41533-019-0161-7

Abstract

Patients treated for drug addiction have high asthma and COPD prevalence rates. The relative contributions of cigarette smoking, smoking intensity and possible smoking of other substances has not been described. We aimed to describe the prevalence and determinants of asthma and COPD in patients prescribed methadone as opioid substitution therapy (OST). In a cross-sectional study of an anonymised patient-level primary care dataset of UK inner-city general practices (n = 46), 321,395 patients aged ≥18 years were identified. A total of 676 (0.21%) had a record of a methadone ever issued in primary care. The association between respiratory disease and methadone prescribing was examined using logistic regression. Models were adjusted for potential effects of clustering by practice. A total of 97.3% of patients prescribed methadone were cigarette smokers, either current (81.2%) or ex-smokers (16.1%). The prevalences of asthma and COPD were higher in methadone patients (14.2% and 12.4%, respectively) compared to non-methadone patients (4.4% and 1.1%, respectively). Methadone was an independent determinant of asthma, adjusting for smoking status (OR 3.21; 95% CI: 2.52, 4.10) or for smoking intensity (3.08; 2.27, 4.19), and of COPD, adjusting for smoking status (6.00; 4.61, 7.80) or for smoking intensity (5.80; 4.12, 8.17). COPD and asthma prevalence were substantially higher in those prescribed methadone compared to those never prescribed methadone. Prescription of methadone was an independent predictor for both COPD and asthma, even after adjustment for smoking status and smoking intensity. Possible explanations include confounding by association with smoking of heroin or crack cocaine, both of which may have a causal association with COPD and asthma.

Highlights

Opioid dependency is the most common addiction among patients seeking treatment for substance misuse.[1]
Coded data on behavioural factors such as self-care and social support. This is the first study to show that chronic obstructive pulmonary disease (COPD) and asthma prevalence are substantially higher in those prescribed methadone compared to those never prescribed methadone, even after adjustment for high smoking rates and smoking intensity
COPD disease severity may be estimated from primary care records using annual Quality and Outcomes Framework (QOF) recording of spirometry findings

Summary

Introduction

Opioid dependency is the most common addiction among patients seeking treatment for substance misuse.[1] In England, of almost 300,000 adults in contact with structured addiction treatment programmes, just over half were receiving treatment for opioid dependency with ~20% treated in primary care.[1,2]. Injecting drug users accounted for almost half of patients entering drug treatment.[1,3] Since 2003, the proportion of heroin users aged over 40 years entering treatment has trebled, constituting an ageing cohort effect.[4]. Substitution therapy with opioid agonists is the mainstay of treatment for patients addicted to opiates. Randomised controlled trials provide evidence of the effectiveness of opioid substitution therapy (OST), such as methadone replacement, in healthcare settings.[5,6] Treatment benefits include harm reduction related to drug-seeking behaviour, reduced rates of blood-borne infections and fatal overdose.[7,8,9] OST increases the overall time to heroin relapse and maximum consecutive days of abstinence when compared with placebo.[7]

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