Characterizing alcohol and drug positivity among adult pedestrians injured in motor vehicle-pedestrian collisions: A level I trauma center study (2007-2022).

PURPOSE: While prior research has documented substance involvement among pedestrians injured in motor-vehicle collisions, fewer studies have examined how alcohol and drug positivity varies across temporal, demographic, and socioeconomic characteristics. This study characterized alcohol and drug positivity among adult pedestrians injured in motor vehicle-pedestrian collisions and examined variation in positivity across these characteristics. METHODS: Patient-level data were retrospectively obtained for adult pedestrians (≥18 years) evaluated at Memorial Hermann-Texas Medical Center following trauma activation for motor vehicle-pedestrian collisions between 2007 and 2022. The study included 3220 injured pedestrians treated at this Level I trauma center in Houston, Texas. Data included age, sex, race/ethnicity, date and time of injury, residential ZIP code, clinical outcomes, blood alcohol concentration (BAC), and urine toxicology results for amphetamines, barbiturates, marijuana, cocaine, opiates, benzodiazepines, and phencyclidine (PCP). Alcohol and drug testing were performed according to institutional trauma evaluation practices and were not universal. Descriptive and bivariate analyses examined substance positivity across temporal, demographic, and area-level socioeconomic characteristics. RESULTS: Of the 3220 injured pedestrians, 2136 (66.3%) underwent alcohol testing and 975 (30.3%) underwent drug testing. Among those tested, 40.4% (n = 862) were positive for alcohol and 83.8% (n = 817) for at least one drug. Alcohol positivity was highest during early morning and evening periods and was significantly higher among males. Alcohol positivity also varied significantly by age, peaking among pedestrians aged 35-49 years and declining substantially among those aged ≥ 65 years. Drug positivity also varied significantly by age. Pedestrians residing in more socioeconomically disadvantaged ZIP codes accounted for a greater share of injuries, and drug positivity differed significantly across quartiles of socioeconomic disadvantage, with generally higher positivity among residents of more disadvantaged areas. CONCLUSION: Substance positivity among injured pedestrians varied across temporal, demographic, and socioeconomic characteristics. Higher nighttime alcohol positivity and drug positivity among pedestrians residing in lower-SES areas highlight opportunities for targeted pedestrian-safety and public-health interventions. More systematic toxicological testing and linkage of trauma records with crash, roadway, and neighborhood-level data could improve understanding of substance involvement and inform prevention strategies.