title: Readmissions after hospitalization for heart failure, acute myocardial infarction, or pneumonia among young and middle-aged adults: a retrospective observational cohort study.
abstract: BACKGROUND
  Patients aged ≥ 65 years are vulnerable to readmissions due to a transient period of generalized risk after hospitalization. However, whether young and middle-aged adults share a similar risk pattern is uncertain. We compared the rate, timing, and readmission diagnoses following hospitalization for heart failure (HF), acute myocardial infarction (AMI), and pneumonia among patients aged 18-64 years with patients aged ≥ 65 years.
  
  
  RESULTS
  We used an all-payer administrative dataset from California consisting of all hospitalizations for HF (n=206,141), AMI (n=107,256), and pneumonia (n=199,620) from 2007-2009. The primary outcomes were unplanned 30-day readmission rate, timing of readmission, and readmission diagnoses. Our findings show that the readmission rate among patients aged 18-64 years exceeded the readmission rate in patients aged ≥ 65 years in the HF cohort (23.4% vs. 22.0%, p<0.001), but was lower in the AMI (11.2% vs. 17.5%, p<0.001) and pneumonia (14.4% vs. 17.3%, p<0.001) cohorts. When adjusted for sex, race, comorbidities, and payer status, the 30-day readmission risk in patients aged 18-64 years was similar to patients ≥ 65 years in the HF (HR 0.99; 95%CI 0.97-1.02) and pneumonia (HR 0.97; 95%CI 0.94-1.01) cohorts and was marginally lower in the AMI cohort (HR 0.92; 95%CI 0.87-0.96). For all cohorts, the timing of readmission was similar; readmission risks were highest between days 2 and 5 and declined thereafter across all age groups. Diagnoses other than the index admission diagnosis accounted for a substantial proportion of readmissions among age groups <65 years; a non-cardiac diagnosis represented 39-44% of readmissions in the HF cohort and 37-45% of readmissions in the AMI cohort, while a non-pulmonary diagnosis represented 61-64% of patients in the pneumonia cohort.
  
  
  CONCLUSIONS
  When adjusted for differences in patient characteristics, young and middle-aged adults have 30-day readmission rates that are similar to elderly patients for HF, AMI, and pneumonia. A generalized risk after hospitalization is present regardless of age. Please see later in the article for the Editors' Summary.
authors.affiliation: Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, Connecticut, United States of America.
authors.forename: Isuru
authors.initials: I
authors.lastname: Ranasinghe
authors.affiliation: Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, Connecticut, United States of America.
authors.forename: Yongfei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, Connecticut, United States of America; Division of Cardiology, Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Kumar
authors.initials: K
authors.lastname: Dharmarajan
authors.affiliation: Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, Connecticut, United States of America.
authors.forename: Angela F
authors.initials: AF
authors.lastname: Hsieh
authors.affiliation: Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, Connecticut, United States of America.
authors.forename: Susannah M
authors.initials: SM
authors.lastname: Bernheim
authors.affiliation: Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, Connecticut, United States of America; Division of Cardiology, Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut, United States of America; The Robert Wood Johnson Clinical Scholars Program, Department of Internal Medicine, School of Medicine, Yale University, New Haven, Connecticut, United States of America; Health Policy and Management, School of Public Health, Yale University, New Haven, Connecticut, United States of America.
authors.forename: Harlan M
authors.initials: HM
authors.lastname: Krumholz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D006760:Hospitalization / Q000639:trends; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D010359:Patient Readmission / Q000639:trends*; D011014:Pneumonia / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D012189:Retrospective Studies; D055815:Young Adult