Prevalence and Incidence Trends for Diagnosed Prescription Opioid Use Disorders in the United Kingdom.

ABSTRACT

INTRODUCTION: The prevalence of prescription opioid use disorders in the US has increased markedly in parallel with increases in opioid prescribing. Whilst an increase in opioid prescribing has also occurred in the UK, it remains unknown if there have been concurrent increases in opioid use disorders. The aim of this study was to examine national trends in the prevalence and incidence of physician-diagnosed opioid use disorders in the UK. METHODS: In a retrospective electronic health care database analysis using data from the UK Clinical Practice Research Datalink (CPRD), we identified persons receiving a first opioid prescription between January 1, 2008 and December 31, 2012. Persons with an opioid use disorder were identified by Read codes assigned by patients' physicians within 6 months following an opioid prescription. We calculated prevalence and incidence rates by dividing the analysis population by the total number of patients exposed (prevalence) or the total patient-years of exposure (incidence) using the 'exact' Clopper-Pearson Binomial method. RESULTS: Our analysis included 714,699 person-years of prescription opioid exposure. The 5-year period prevalence of opioid use disorders was 4.61 (95% CI 4.28-4.96) per 10,000 individuals, or 0.05%. The incidence rate of opioid use disorders was of 6.51 (95% CI 5.93-7.13) patients per 10,000 patient-years exposed. When examined by study year, there was no clear suggestion of a changing trend over time. When stratified by opioid drug, trends in the incidence rate during the study were either stable (i.e., codeine and tramadol), increasing (i.e., morphine) or decreasing (i.e., dihydrocodeine). CONCLUSIONS: Our study demonstrates that despite the marked increase in overall opioid prescribing in the UK in the past decade, there has not been an increase in the incidence of physician-diagnosed opioid use disorders.