title: The epidemiology of hospitalised acute kidney injury not requiring dialysis in England from 1998 to 2013: retrospective analysis of hospital episode statistics.
abstract: OBJECTIVE
  Epidemiology studies of acute kidney injury (AKI) have focused on cases requiring dialysis but those not requiring dialysis represent the majority. To address this gap, we interrogated hospital episode statistics (HES) to investigate population trends in temporal epidemiology of AKI not requiring dialysis between 1998 and 2013.
  
  
  METHODS
  In this retrospective observational study of HES data covering the entire English National Health Service, we identified 1,136,167 AKI events, not requiring dialysis, diagnosed between 1998 and 2013. We explored the effect of age, gender, ethnicity, Charlson's comorbidity score (CCS), method of admission, diagnosis period and AKI in diagnosis codes on temporal changes in the incidence and case-fatality of AKI with specific examination of its predictors.
  
  
  RESULTS
  The incidence of AKI increased from 15,463 cases (317 pmp) in 1998-1999 to 213,700 cases (3995 pmp) in 2012-2013. There was increase in proportion of people over 75 years from 51.1% in 1998-1999 to 63.4% in 2012-2013. Overall unadjusted case-fatality decreased from 42.3% in 1998-2003 to 27.1% in 2008-2013, p < 0.001. Compared with 1998-2003, the multivariable adjusted odds ratio for death was 0.64 in 2003-2008 (95% CI 0.63-0.65) and 0.35 in 2008-2013 (95% CI 0.34-0.35). Odds for death were higher for patients over 85 years (2.93; 95% CI 2.89-2.97), CCS of more than five (2.75; 95% CI 2.71-2.79), emergency admissions (2.14; 95% CI 2.09-2.18) and AKI in the secondary diagnosis code (1.35; 95% CI 1.33-1.36) and AKI in other diagnoses codes (2.17; 95% CI 2.15-2.20).
  
  
  CONCLUSIONS
  In England, the incidence of AKI not requiring dialysis has increased and case-fatality has decreased over last 15 years. Efforts to reduce the incidence of AKI and improve survival should focus on elderly people, emergency admissions and those with multi-morbidity.
authors.affiliation: Department of Renal Medicine, Royal Derby Hospital, Derby, UK.
authors.forename: N V
authors.initials: NV
authors.lastname: Kolhe
authors.affiliation: Derby City Council, The Council House, Derby, UK.
authors.forename: A W
authors.initials: AW
authors.lastname: Muirhead
authors.affiliation: Division of Rheumatology, Orthopaedics and Dermatology, School of Medicine, University of Nottingham, Nottingham, UK.
authors.forename: S R
authors.initials: SR
authors.lastname: Wilkes
authors.affiliation: Department of Renal Medicine, Royal Derby Hospital, Derby, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Fluck
authors.affiliation: Department of Renal Medicine, Royal Derby Hospital, Derby, UK.|Division of Medical Sciences and Graduate Entry Medicine, University of Nottingham, Derby, UK.
authors.forename: M W
authors.initials: MW
authors.lastname: Taal
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D004739:England / Q000453:epidemiology; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D017052:Hospital Mortality / Q000639:trends; D006760:Hospitalization / Q000639:trends*; D006801:Humans; D015994:Incidence; D008297:Male; D016017:Odds Ratio; D006435:Renal Dialysis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index