To assess the association between the length of consistent primary care as part of an accountable care organization (attribution length) and population-level and same-hospital readmissions. Readmission studies are generally focused on same-hospital readmissions rather than readmissions to any hospital (population-level readmissions).

A retrospective study of Medicaid claims data for 28 794 unique pediatric patients attributed to a single children's hospital between September 2013 and May 2015. Study used logistic regression to estimate the impact of attribution length on readmissions and a zero-inflated Poisson model to assess the impact of attribution length on readmission cost and readmission days.

The study showed attribution length was associated with a significant reduction in the population-level 30-day readmission rate from 8.9%-6.2% (P = .010) primarily by reducing readmissions that occurred at hospitals other than the discharging hospital. There was no significant reduction in the same-hospital readmission rate. Readmissions to a different hospital occurred in 37% of readmissions. Although not significant at the P = .05 level, attribution length was associated with a 44% reduction (P = .100) in 30-day readmission costs or a 5.0% reduction in the cost of an inpatient episode of care and a 53% reduction (P = .019) in readmission days.

Consistent primary care (attribution length) may be able to reduce 30-day, pediatric Medicaid patients' readmissions at the population level. The decrease occurred primarily in readmissions to hospitals other than the discharging hospital. There was no decrease in the rate of same-hospital readmissions.