Association of nonfatal overdose surveillance data with concurrent and future overdose deaths in Rhode Island

Given substantial reporting delays in overdose deaths, state health departments increasingly use non-fatal overdose data to inform geographically targeted rapid overdose response efforts. We sought to evaluate the extent to which non-fatal overdose events were associated with concurrent and future overdose deaths in Rhode Island. We aggregated non-fatal overdose data from emergency medical services records (2019-2023) and fatal overdose data from the State Unintentional Drug Overdose Reporting System (2020-2023) in 1-, 3-, and 6-month intervals at census block group and census tract levels. Rates of fatal overdose were estimated, relative to non-fatal overdose lagged by 0-12 months, using negative binomial regression, and relative to monthly spikes in non-fatal overdose burden, using zero-inflated Poisson regression. Estimation was implemented using integrated nested Laplace approximation. Each additional non-fatal overdose event per census block group was associated with fatal overdose rates that were 48% higher (95% credible interval: 1.37-1.59) than expected in concurrent months, with smaller associations at the census tract level, in wider time intervals, and when non-fatal overdose data were lagged. Spikes in non-fatal overdose activity were associated with elevated overdose mortality in concurrent periods with fine temporal and geographic granularity, but not in larger time frames and geographic areas.