Proximity and emergency department use: Multilevel analysis using administrative data from patients with cardiovascular risk factors

Abstract

Objective: To determine if geographic proximity to an emergency department (ED) is related to ED use in a metropolitan population of patients with cardiovascular risk factors.

Design: Population-based, retrospective cohort study.

Setting: The census metropolitan area of Montreal, Que.

Participants: Cohort of 99 400 patients with diabetes, hypertension, or dyslipidemia in 2007 without a history of cardiovascular disease. Each patient was spatially referred to 1 of 5857 dissemination areas (DAs).

Main outcome measures: Annual number of visits to an ED with respect to the distance between the centroid of a patient's DA and the closest ED, controlling for age, sex, comorbidities, and neighbourhood immigration, social, and material characteristics. Multilevel logistic and negative binomial regressions were used to determine if the proximity to the closest ED was related to ED use, frequent ED use (≥ 4 visits in a year), and number of ED visits.

Results: A total of 25 889 (26.0%) patients in the cohort visited an ED at least once during a 1-year period, among which 4563 (4.6%) were frequent users with at least 4 visits. These frequent users were responsible for 28 249 (45.5%) of all 62 021 visits to EDs. The distance between a DA and its closest ED was significantly and negatively correlated with ED use (P < .001), even after controlling for confounding variables. Patients living in a DA close to an ED were also more likely to be frequent users, but the extent of use among them (range from 4 to 82 ED visits) was not related to the distance to the closest ED.

Conclusion: These results suggest that patients at risk of cardiovascular disease living in a metropolitan area are more likely to seek a medical encounter at the ED if they live closer to it.

Figures

Figure 1.

Distribution of EDs in the census metropolitan area of Montreal in Quebec ED—emergency department.

Figure 2.

Study cohort CMA-M—census metropolitan area of Montreal, CVD—cardiovascular disease, ICD—International Classification of Diseases. *A patient was considered to be at risk of CVD if he or she had received a primary or secondary diagnosis of hypertension (ICD-9 code 401, ICD-10 code I10), diabetes (ICD-9 code 250, ICD-10 code E10–E14), or dyslipidemia (ICD-9 code 272, ICD-10 code E78) during a hospitalization or at least 3 physician claims within 1 y with an identical diagnosis. †A patient could be present in more than 1 disease-specific cohort (eg, a patient with hypertension could also have diabetes).

Figure 3.

Cumulative number of ED visits in the 1-year follow-up period according to the cumulative proportion of patients ED—emergency department. *By reverse order of the number of ED visits.

Figure 4.

Crude and adjusted ORs for the probability of being an ED user and a frequent ED user (among ED users) according to distance to EDs:The reference group was patients living 10 km or farther from EDs. ED—emergency department, OR—odds ratio.