"When" matters: Differences in fatal opioid-related overdose events in Massachusetts by time of day, 2019-2023

Geospatial analyses of opioid involved overdose deaths can inform community harm reduction efforts. Differences in overdose deaths by time of day are important, as overdose events may be more likely to go unrecognized at night when fewer community resources are available.

Using Massachusetts Registry of Vital Records and Statistics data (2019-2023), we utilized regression analyses to evaluate demographics, residence, and toxicology differences associated with the recorded time of opioid involved overdose deaths, stratified by day (6AM-5:59PM) and night (6PM-5:59AM). Kernel density estimates and hotspot clusters assessed location differences and proximity to opioid treatment resources.

Of 9539 opioid-involved overdose deaths, 6255 (65.6%) occurred during daytime hours and 3284 (34.4%) at night. Non-Hispanic Black individuals (OR 1.14; 95%CI 1.01-1.28) and married individuals (OR 1.19; 95%CI 1.04-1.35) were more likely to have a recorded time of overdose death at night. Alcohol was more likely to be present among people who experienced an opioid involved overdose death at night (OR 1.23; 95%CI 1.11-1.37). Decedents were more likely to have the hospital as their location of death at night (OR 2.24, 95%CI 2.01-2.48). Proximity to treatment and harm reduction resources did not differ by time of day (OR 1.02, 95%CI 0.88-1.13).

While time of day was not associated with differences in proximity to opioid treatment resources, several demographic and toxicology characteristics were associated with opioid-involved overdose deaths at night. Harm reduction strategies must evolve beyond "where" services are located to address when and how harm reduction is delivered.