The association between prescription opioid dispensing and opioid-related morbidity and mortality in Ontario, Canada: an ecological study of public health units.

OBJECTIVE Overdose and death rates from opioids continue to rise. However, the relative contribution of prescription opioids to the ongoing crisis is unclear. The purpose of this study was to assess the association between prescription opioid dispensing and opioid-related morbidity and mortality. METHODS Regional-level data for this ecological study were extracted from publicly available databases for the years 2013-2018 in Ontario, Canada. The primary exposure variable was opioids dispensed, in milligram morphine equivalents (MME), per capita by public health unit (PHU) in a given year. The primary outcome was the rate of opioid-related emergency department (ED) visits per 100,000 by PHU. Generalized estimating equation (GEE) analytic models were developed to account for clustering by PHU over time while adjusting for demographic and population health characteristics at the regional level. RESULTS Higher per capita MME of opioids dispensed was associated with lower rates of opioid-related ED visits per 100,000 (β=-0.091, 95 % CI: -0.110 to -0.077, p < 0.001), as well as with lower rates of opioid-related deaths per 100,000 (β=-0.012, 95 % CI: -0.014 to -0.007, p < 0.001). In subgroup analyses based on time periods (2016-2018 vs. 2013-2015), this negative association was seen only for the period 2016-2018. INTERPRETATION Higher per capita regional opioid prescribing was not positively associated with an increased rate of opioid-related emergency room visits or opioid-related deaths. Further studies with patient-level data are needed to better understand our findings.