Rural-Urban Variations in the Association Between Substance Use and Pre-Hospital Crash Injury Severity Among Older Adults: A Single Year National Cross-sectional Study

Background This study aims to assess the rural-urban differences between substance use and crash injury severity among older adults. Methods This single-year cross-sectional analysis pooled the 2019 data from the National Emergency Medical Service Information System. We measured injury severity (low acuity, emergent, critical, and fatal) as predicted by substance use, defined as self-reported or officer-reported alcohol and/or drug use. We controlled for age, sex, road user type, anatomical injured region, revised trauma score, location (scene) of the injury, and the time of the day. We stratified by rurality/urbanicity and performed a partial proportional ordinal logistic regression. We reported the odds of worse injury outcomes (emergent, critical, and fatal injuries) compared to low acuity injuries and the predicted probabilities of each injury category by rurality/urbanicity. Results Our sample consisted of 58,238 older adults, who sustained crash injuries. Approximately 69%, 25%, 5%, and 1% sustained low acuity, emergent, critical, and fatal injuries, respectively. Substance use was reported in approximately 4% of the sample population, and this proportion did not significantly differ across rural-urban areas. After controlling for patient and injury characteristics, substance use was associated with 45% increased odds of emergent, critical, and fatal injuries compared to low acuity injuries across all areas. The predicted probabilities of critical and emergent injuries increase from urban to suburban and rural areas. Conclusion Substance use is associated with worse geriatric crash injury severity and the predicted probabilities of substance use-related emergent and critical crash injuries increase from urban to rural areas. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data is available upon request from the National Emergency Medical Service Information System