title: Acute admissions to medical departments in Denmark: diagnoses and patient characteristics.
abstract: BACKGROUND
  Despite extensive research on individual diseases, population-based knowledge about reasons for acute medical admissions remains limited. Our aim was to examine primary diagnoses, Charlson Comorbidity Index (CCI) score, age, and gender among patients admitted acutely to medical departments in Denmark.
  
  
  METHODS
  In this population-based observational study, 264,265 acute medical patients admitted during 2010 were identified in the Danish National Registry of Patients (DNRP), covering all hospitals in Denmark. Reasons for acute admissions were assessed by primary diagnoses, grouped according to the International Classification of Diseases 10th edition. Additionally, the CCI score, age and gender were presented according to each diagnostic group.
  
  
  RESULTS
  Two-thirds of the patients had one of the four following reasons for admission: cardiovascular diseases (19.3%), non-specific Z-diagnoses ("Factors influencing health status and contact with health services") (16.9%), infectious diseases (15.5%), and non-specific R-diagnoses ("Symptoms and abnormal findings, not elsewhere classified") (11.8%). In total, 45% of the patients had a CCI score of one or more and there was a considerable overlap between the patients' chronic diseases and the reason for admission. The median age of the study population was 64 years (IQR 47-77 years), ranging from 46 years (IQR 27-66) for injury and poisoning to 74 years (IQR 60-83) for hematological diseases. Gender representation varied considerably within the diagnostic groups, for example with male predominance in mental disorders (59.0%) and female predominance in diseases of the musculoskeletal system (57.8%).
  
  
  CONCLUSIONS
  Our study identifies that acute medical patients often present with non-specific symptoms or complications related to their chronic diseases.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Denmark. Electronic address: bh@dce.au.dk.
authors.forename: Betina
authors.initials: B
authors.lastname: Vest-Hansen
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Denmark.
authors.forename: Anders Hammerich
authors.initials: AH
authors.lastname: Riis
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Denmark.
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sørensen
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Denmark.
authors.forename: Christian Fynbo
authors.initials: CF
authors.lastname: Christiansen
mesh_terms: D000208:Acute Disease / Q000453:epidemiology* / Q000628:therapy*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059019:Clinical Coding / Q000379:methods*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010343:Patient Admission / Q000706:statistics & numerical data* / Q000639:trends; D012042:Registries; D012189:Retrospective Studies; D055815:Young Adult
keywords: Comorbidity; Diagnosis; Epidemiology; Hospitalization; Internal medicine; International classification of diseases