Examining correlations between opioid dispensing and opioid-related hospitalizations in Canada, 2007–2016

BACKGROUND: High levels of opioid-related mortality, as well as morbidity, contribute to the excessive opioid-related disease burden in North America, induced by high availability of opioids. While correlations between opioid dispensing levels and mortality outcomes are well-established, fewer evidence exists on correlations with morbidity (e.g., hospitalizations). METHODS: We examined possible overtime correlations between medical opioid dispensing and opioid-related hospitalizations in Canada, by province, 2007–2016. For dispensing, we examined annual volumes of medical opioid dispensing derived from a representative, stratified sample of retail pharmacies across Canada. Raw dispensing information for ‘strong opioids’ was converted into Defined Daily Doses per 1000 population per day (DDD/1000/day). Opioid-related hospitalization rates referred to opioid poisoning-related admissions by province, for fiscal years 2007–08 to 2016–17, drawn from the national Hospital Morbidity Database. We assessed possible correlations between opioid dispensing and hospitalizations by province using the Pearson product moment correlation; correlation values (r) and confidence intervals were reported. RESULTS: Significant correlations for overtime correlations between population-levels of opioid dispensing and opioid-related hospitalizations were observed for three provinces: Quebec (r = 0.87, CI: 0.49–0.97; p = 0.002); New Brunswick (r = 0.85;CI: 0.43–0.97; p = 0.004) and Nova Scotia (r = 0.78; CI:0.25–0.95; p = 0.012), with an additional province, Saskatchewan, (r = 0.073; CI:-0.07–0.91;p = 0.073) featuring borderline significance. CONCLUSIONS: The correlations observed further add to evidence on opioid dispensing levels as a systemic driver of population-level harms. Notably, correlations were not identified principally in provinces with reported high contribution levels (> 50%) of illicit opioids to mortality, which are not captured by dispensing data and so may have distorted or concealed potential correlation effects due to contamination.