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 nonfatal overdose data to inform geographically targeted rapid overdose response efforts. We evaluated the extent to which nonfatal overdose events were associated with concurrent and future overdose deaths in Rhode Island. We aggregated nonfatal 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 nonfatal overdose lagged by 0-12 months, using negative binomial regression, and relative to monthly spikes in nonfatal overdose burden, using zero-inflated Poisson regression. Estimation was implemented using integrated nested Laplace approximation. Each additional nonfatal 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 nonfatal overdose data were lagged. Spikes in nonfatal overdose activity were associated with elevated overdose mortality in concurrent periods with fine temporal and geographic granularity, but not in longer time frames and larger geographic areas.