Filling in the gaps: A geospatial approach to optimizing placement of methadone clinics in Massachusetts

Methadone treatment dispensed at opioid treatment programs (OTPs) reduces the risk of fatal opioid-related overdose. Access to OTPs is limited in many regions. We utilized location-allocation models to identify gaps in OTP services across Massachusetts and generated descriptive statistics to further prioritize areas for expansion of services for socially vulnerable communities.

We used a geographic information system to generate eight location-allocation models, tools to target the placement of new sites based on the distribution of existing sites and demand for services, with a goal of identifying gaps in geographic access to OTPs. We identified potential new OTP locations using 15- and 30-minute walk- and drive-times, considering the location of existing OTPs. We used opioid-related incident (ORI) locations and overdose decedent residences to measure methadone demand. We ranked suggested OTPs for each model by how many ORIs or decedent residences they could serve as the nearest OTP. We calculated mean Social Vulnerability Index scores, population density, fatal opioid-related overdose rates, and ORI rates for census tracts within a 30-minute walk of each suggested site. We also ran supplementary location-allocation analyses that ignored the locations of existing OTPs.

Our models consistently recommended new OTP service locations to address unmet needs in the Roxbury and Dorchester neighborhoods of Boston, Lowell, Pittsfield, New Bedford, Gardner, Quincy, Malden, Peabody, Falmouth, Nantucket, and Martha's Vineyard, Massachusetts. Of all suggested new treatment centers, those in Boston, Gardner, Peabody, and Lowell could serve as the closest OTP for the most ORIs or decedent residences. Suggested new OTPs in Boston, Gardner, Springfield, Quincy, New Bedford, and Lowell were in areas with high social vulnerability. Our walk-time models suggested sites in areas with higher community-level social vulnerability than our drive-time models. Areas with existing OTPs had higher average social vulnerabilities than suggested new OTP locations. Location-allocation models that ignored existing OTPs still suggested OTP locations close to current methadone clinics.

Through our location-allocation models and vulnerability assessments, we recommended potential locations for new OTPs to provide increased methadone access within areas of high fatal overdose and ORI burden. Results can inform data-to-action expansion of OTP access.