Neighborhood Poverty and 9-1-1 Ambulance Contacts.

BACKGROUND: Neighborhood poverty is positively associated with frequency of 9-1-1 ambulance utilization, but it is unclear whether this association remains significant when accounting for variations in the severities and types of ambulance contacts. METHODS: We merged EMS ambulance contact records in a single California county (n = 88,027) with data from the American Community Survey at the census tract level (n = 300). Using tract as a proxy for neighborhood and negative binomial regression as an analytical tool, we predicted 16 outcomes: any ambulance contacts, ambulance contacts stratified by three intervention severities, and ambulance contacts varied by 12 primary impression categories. For each model, we estimated the incident rate ratios for 10 percentage point increases in tract-level poverty while controlling for geographic patterns in race, citizenship, gender, age, emergency department proximity, population density, and population size. RESULTS: Our study produced three major findings. First, tract-level poverty was positively associated with ambulance contacts (incident rate ratio [IRR] 1.45; 95% confidence interval [CI] 1.34 to 1.57). Second, poverty was positively associated with low severity contacts (IRR 1.48; 95% CI 1.35 to 1.61), medium severity contacts (IRR 1.38; 95% CI 1.28 to 1.49), and high severity contacts (IRR 1.40; 95% CI 1.30 to 1.51). Third, poverty was positively associated with 12 primary impression categories: abdominal (IRR 1.48; 95% CI 1.36 to 1.61), altered level of consciousness (IRR 1.37; 95% CI 1.25 to 1.50), cardiac (IRR 1.28; 95% CI 1.14 to 1.42), overdose/intoxication (IRR 1.59; 95% CI 1.40 to 1.81), pain (IRR 1.56; 95% CI 1.41 to 1.73), psych/behavioral (IRR 1.50; 95% CI 1.34 to 1.67), respiratory (IRR 1.42; 95% CI 1.29 to 1.56) seizure (IRR 1.52; 95% CI 1.38 to 1.68), stroke (IRR 1.14; 95% CI 1.01 to 1.28), syncope/near syncope (IRR 1.23; 95% CI 1.12 to 1.36), trauma (IRR 1.44; 95% CI 1.31 to 1.58), and general weakness (IRR 1.31; 95% CI 1.20 to 1.42). CONCLUSION: Our study suggests poverty is a positive, strong, and enduring predictor of ambulance contacts at the neighborhood level. The relationship between neighborhood poverty and ambulance utilization should be considered at multiple levels of EMS decision making.