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

Abstract 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 from a representative, stratified sample of retail pharmacies across Canada. Raw dispensing information for ‘strong opioids’ was converted into Defined Daily Doses (DDD)/per 1,000 population/year. 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 Saskatchewan (r=0.073; CI:-0.07–0.91;p=0.073) featuring borderline significance. Conclusions: The correlations observed further contribute 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 potential effects due to contamination.