Fatal opioid-related overdoses (OOD) remain one of the most significant public health challenges in the US (National Center for Health Statistics, 2021). The current OOD epidemic has been characterized nationally by four waves tied to: prescription opioids beginning in 1999; heroin beginning in 2010; synthetic opioids, largely driven by illicitly manufactured fentanyl, beginning in 2013; and stimulants, such as cocaine and methamphetamine, in combination with fentanyl or other opioids, beginning in 2019 (Ciccarone, 2021, Post et al., 2022). Since March 2020, the COVID-19 pandemic has compounded risks among people who use drugs, with added stress, isolation, and economic disadvantage, and increased OOD hazards (Slavova et al., 2020, Walters et al., 2020). OOD mortality rates increased five-fold in Massachusetts between 2000 and 2021 (MDPH, 2022a), becoming ubiquitous across the Commonwealth between 2011 and 2015 (MDPH, 2017), and then further exacerbated by shifts in risk across different racial and ethnic populations, with disproportional increases during recent years within communities of color (MDPH, 2022b).

The risk environment of OOD continues to shift dynamically. New substances and adulterants, in addition to fentanyl and its analogs, have been introduced in drug supplies across the US, contributing to large increases in OOD (MDPH, 2022a, National Center for Health Statistics, 2021). Xylazine, for instance, a veterinary tranquilizer, has been increasingly linked to OOD and soft tissue infections (Friedman et al., 2022, Kariisa et al., 2021). More recently, nitazene analogs, a novel class of synthetic opioids 40 times more potent than fentanyl, were reported to be associated with fatal overdoses in Philadelphia (Bettigole et al., 2022). Patterns in fatal OOD risk are also dynamic across geographic regions in both urban and rural communities (Korthuis et al., 2022, Nolte et al., 2022). This dynamic pattern is likely a result of shifts in the drug supply,(Ciccarone, 2017) changes in substance use patterns (Jalal et al., 2018), varying levels in deployment of opioid use disorder (OUD) treatment and overdose prevention programs (Walley et al., 2013), and changes in socio-demographic fatal OOD risks across racial and ethnic groups (MDPH, 2022b).

Recent studies have begun to elucidate the spatiotemporal impacts of the four waves of the fatal OOD epidemic across different subpopulations in the US (Jalal et al., 2018, Stewart et al., 2017). Novel analytical and visualization techniques have been introduced to assess OOD trends by demographic, geographic, and substance use risk profiles (Stopka et al., 2019). More intuitive and replicable analytical approaches are needed to assist local and state public health officials to better understand nuanced aspects of local OOD trends and inform targeted responses.

As part of a larger NIH-funded study focused on the use of Bayesian spatiotemporal analyses to predict fatal OOD to inform pre-emptive public health responses, we combined temporal and geostatistical analyses to better understand the historical patterns of fatal OOD in Massachusetts. Our analyses highlight the dynamic temporal and spatial trends in fatal OOD by implicated substance, rurality, age, and racial and ethnic subpopulations, and can inform OOD policy and intervention targeting.