Ambulatory Care Fragmentation, Emergency Department Visits, and Race: a Nationwide Cohort Study in the U.S

Background: It is unclear whether highly fragmented ambulatory care (i.e., care spread across multiple providers without a dominant provider) increases the risk of an emergency department (ED) visit. Whether any such association varies with race is unknown.

Objective: We sought to determine whether highly fragmented ambulatory care increases the risk of an ED visit, overall and by race.

Design and participants: We analyzed data for 14,361 participants ≥ 65 years old from the nationwide prospective REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort study, linked to Medicare claims (2003-2016).

Main measures: We defined high fragmentation as a reversed Bice-Boxerman Index ≥ 0.85 (≥ 75^th percentile). We used Poisson models to determine the association between fragmentation (as a time-varying exposure) and ED visits, overall and stratified by race, adjusting for demographics, medical conditions, medications, health behaviors, psychosocial variables, and physiologic variables.

Key results: The average participant was 70.5 years old; 53% were female, and 33% were Black individuals. Participants with high fragmentation had a median of 9 visits to 6 providers, with 29% of visits by the most frequently seen provider; participants with low fragmentation had a median of 7 visits to 3 providers, with 50% of visits by the most frequently seen provider. Overall, high fragmentation was associated with more ED visits than low fragmentation (adjusted risk ratio [aRR] 1.31, 95% confidence interval [CI] 1.29, 1.34). The magnitude of this association was larger among Black (aRR 1.48, 95% CI 1.44, 1.53) than White participants (aRR 1.23, 95% CI 1.20, 1.25).

Conclusions: Highly fragmented ambulatory care was an independent predictor of ED visits, especially among Black individuals.