Regional and temporal variation in methamphetamine-related incidents: applications of spatial and temporal scan statistics

Abstract

Introduction. This investigation utilized spatial scan statistics, geographic information systems, and multiple data sources to assess spatial clustering of statewide methamphetamine-related incidents. Temporal and spatial associations with regulatory interventions to reduce access to precursor chemicals (pseudoephedrine) were also explored. Methods. Four statewide data sources were utilized including regional poison control center statistics, fatality incidents, methamphetamine laboratory seizures, and hazardous substance releases involving methamphetamine laboratories. Spatial clustering of methamphetamine incidents was assessed using SaTScan™. SaTScan™ was also utilized to assess space-time clustering of methamphetamine laboratory incidents, in relation to the enactment of regulations to reduce access to pseudoephedrine. Results. Five counties with a significantly higher relative risk of methamphetamine-related incidents were identified. The county identified as the most likely cluster had a significantly elevated relative risk of methamphetamine laboratories (RR = 11.5), hazardous substance releases (RR = 8.3), and fatalities relating to methamphetamine (RR = 1.4). A significant increase in relative risk of methamphetamine laboratory incidents was apparent in this same geographic area (RR = 20.7) during the time period when regulations were enacted in 2004 and 2005, restricting access to pseudoephedrine. Subsequent to the enactment of these regulations, a significantly lower rate of incidents (RR = 0.111, p = 0.0001) was observed over a large geographic area of the state, including regions that previously had significantly higher rates. Conclusions. Spatial and temporal scan statistics can be effectively applied to multiple data sources to assess regional variation in methamphetamine-related incidents, and explore the impact of preventive regulatory interventions.