Journal of General Internal Medicine

, Volume 34, Issue 2, pp 226–234 | Cite as

Risk Assessment of Acute, All-Cause 30-Day Readmission in Patients Aged 65+: a Nationwide, Register-Based Cohort Study

  • Mona K. PedersenEmail author
  • Gunnar L. Nielsen
  • Lisbeth Uhrenfeldt
  • Søren Lundbye-Christensen
Original Research



Hospital readmission is considered an adverse health outcome in older people, adding additional pressure on clinical resources within health care services. Despite numerous studies on risk factors for readmissions, studies find different strengths of respective determinants and there is a need to explore and identify patterns of risk factors in larger cohorts.


Exploring and identifying patterns of risk factors for acute, all-cause 30-day readmission in a Danish cohort of patients aged 65+.


Register-based cohort study using individual-level linkable information on demographics, social determinants, clinical conditions, health care utilization, and provider determinants obtained from primary and secondary health care.


Historic cohort of 1,267,752 admissions in 479,854 patients, aged 65+, discharged from Danish public hospitals from January 2007 to September 2010.

Main Measures

We included patient-level variables and admission-level variables. Outcome was acute, all-cause 30-day readmission. Data was analyzed by univariable and multivariable logistic regression. Strength of associations was analyzed using Wald test statistics. Receiver operating characteristic (ROC) analysis was used for quantification of predictive ability. For validation, we used split-sample design.

Key Results

Acute admission and number of days since previous hospital discharge were factors strongly associated with readmission. Patients at risk of future readmission suffered from comorbidity, consumed more drugs, and were frequent users of in- and outpatient health care services in the year prior to the index admission. Factors related to index admission were only weakly associated with readmission. The predictive ability was 0.709 (0.707–0.711) for acute readmission.


In a general population of older people, we found that pre-hospital factors rather than hospital factors account for increased risk of readmission and are dominant contributors to predict acute all-cause 30-day readmission. Therefore, risk for excess readmission should be shared across sectors and focus the care trajectory over time rather than distinct care episodes.


database health services research readmission risk assessment 



This work was supported by the A.P. Moeller Foundation for the Advancement of Medical Science, Speciallaege Heinrich Kopps Legat, Novo Nordisk Foundation, and The Danish Nursing Research Foundation. They had no role in the design or conduct of this study. We thank the anonymous reviewers for their insightful comments and qualifying suggestions.

Compliance with Ethical Standards

The study was registered under the North Denmark Region’s joint notification of health research (ID 2008-58-0028).

Conflict of Interest

The authors declare that they do not have a conflict of interest.

Supplementary material

11606_2018_4748_MOESM1_ESM.docx (18 kb)
ESM 1 (DOCX 17 kb)


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Copyright information

© Society of General Internal Medicine 2018

Authors and Affiliations

  • Mona K. Pedersen
    • 1
    • 2
    Email author
  • Gunnar L. Nielsen
    • 1
    • 3
  • Lisbeth Uhrenfeldt
    • 4
    • 5
  • Søren Lundbye-Christensen
    • 3
    • 6
  1. 1.Department of Internal Medicine Aalborg University HospitalAalborgDenmark
  2. 2.Clinical Nursing Research UnitAalborg University HospitalAalborgDenmark
  3. 3.Department of Clinical MedicineAalborg UniversityAalborgDenmark
  4. 4.Clinical Nursing Research, Department of Health Science and TechnologyAalborg UniversityAalborgDenmark
  5. 5.Faculty of Nursing and Health SciencesNord UniversityBodøNorway
  6. 6.Unit of Clinical BiostatisticsAalborg University HospitalAalborgDenmark

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