Differences between early and late readmissions among patients: a cohort study.

Background: Early and late readmissions may have different causal factors, requiring different prevention strategies.
Objective: To determine whether predictors of readmission change within 30 days after discharge.
Design: Retrospective cohort study.
Setting: Academic medical center.
Participants: Patients admitted between 1 January 2009 and 31 December 2010.
Measurements: Factors related to the index hospitalization (acute illness burden, inpatient care process factors, and clinical indicators of instability at discharge) and unrelated factors (chronic illness burden and social determinants of health) and how they affect early readmissions (0 to 7 days after discharge) and late readmissions (8 to 30 days after discharge).
Results: 13 334 admissions, representing 8078 patients, were included in the analysis. Early readmissions were associated with markers of acute illness burden, including length of hospital stay (odds ratio [OR], 1.02 [95% CI, 1.00 to 1.03]) and whether a rapid response team was called for assessment (OR, 1.48 [CI, 1.15 to 1.89]); markers of chronic illness burden, including receiving a medication indicating organ failure (OR, 1.19 [CI, 1.02 to 1.40]); and social determinants of health, including barriers to learning (OR, 1.18 [CI, 1.01 to 1.38]). Early readmissions were less likely if a patient was discharged between 8:00 a.m. and 12:59 p.m. (OR, 0.76 [CI, 0.58 to 0.99]). Late readmissions were associated with markers of chronic illness burden, including receiving a medication indicating organ failure (OR, 1.24 [CI, 1.08 to 1.41]) or hemodialysis (OR, 1.61 [CI, 1.12 to 2.17]), and social determinants of health, including barriers to learning (OR, 1.24 [CI, 1.09 to 1.42]) and having unsupplemented Medicare or Medicaid (OR, 1.16 [CI, 1.01 to 1.33]).
Limitation: Readmissions were ascertained at 1 institution.
Conclusion: The time frame of 30 days after hospital discharge may not be homogeneous. Causal factors and readmission prevention strategies may differ for the early versus late periods.
Primary Funding Source: Health Resources and Services Administration, National Institute on Aging, National Institutes of Health, Harvard Catalyst, and Harvard University.