Drugs & Aging

, Volume 27, Issue 1, pp 51–61

Drug-Induced, Dementia-Associated and Non-Dementia, Non-Drug Delirium Hospitalizations in the United States, 1998–2005

An Analysis of the National Inpatient Sample
  • Robert Y. Lin
  • Laura C. Heacock
  • Joyce F. Fogel
Original Research Article



The incidence and pattern of delirium recorded in a broad spectrum of American hospitalizations has not been well described. The National Inpatient Sample (NIS) of the Healthcare Cost and Utilization Project is an administrative database of hospitalizations in the US that affords an opportunity to examine for International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) codes relating to delirium.


To examine the prevalence of delirium diagnoses and associated clinical factors, including adverse drug effects, in a broad spectrum of hospitalizations in the US. Delirium was grouped into three categories: drug-induced delirium, dementia-associated delirium, and non-dementia, non-drug (NDND).


Hospitalizations during the years 1998–2005 in the NIS databases were examined. These databases represent samples of hospitalizations that allow for national prevalence estimates. ICD-9 codes for drug-induced, dementia-associated and NDND delirium were identified in the hospitalizations for each year. Delirium tremens was not considered in this classification, and paediatric and psychiatric admissions were excluded. Yearly prevalence for drug-induced, dementia-associated and NDND delirium were tabulated, and time trends were analysed with negative binomial regression. A hospitalization subset cohort with urinary tract/kidney infection, pneumonia, heart failure and lower extremity orthopaedic surgery diagnosis-related group categories was also analysed for clinical associations with the presence of the three categories of delirium using multinomial logistic regression. ICD-9 E codes (external causes of injury) constituting adverse drug effects were identified and considered as clinical predictors.


Delirium was recorded in 1 269 185 (0.54%) non-psychiatric adult hospitalizations during the study years. Whereas the overall prevalence of dementia-associated delirium and NDND delirium decreased over time, drug-induced delirium prevalence increased (p<0.0001). As expected, the presence of dementia and adverse drug effects had the strongest associations with dementia-associated and drug-induced delirium, respectively, in the cohort hospitalizations. Drug-induced delirium and NDND delirium had the strongest associations with lower extremity orthopaedic surgery hospitalizations and urinary tract/kidney infection hospitalizations, respectively. Among the NDND co-morbid conditions, volume depletion and sodium imbalance had the strongest, albeit modest, associations with delirium. The association between decade of age and delirium was strongest for NDND delirium (adjusted odds ratio 1.53; 95% CI 1.52, 1.53), but age had significant associations with drug-induced and dementia-associated delirium as well. In the cohort, the most frequent adverse effects codes were for opioids and for benzodiazepines or other sedatives, which were noted in 21.3% and 15.2% of drug-induced delirium hospitalizations, respectively.


Drug-induced delirium is being increasingly identified in hospitalized patients. Administrative hospitalization databases constitute a resource to explore factors and trends associated with delirium. The findings suggest that interventions focusing on adverse drug effects have the greatest potential for preventing delirium.


  1. 1.
    Inouye SK. Delirium in older persons. N Engl J Med 2006; 354: 1157–65PubMedCrossRefGoogle Scholar
  2. 2.
    Maldonado JR. Delirium in the acute care setting: characteristics, diagnosis and treatment. Crit Care Clin 2008; 24: 657–722PubMedCrossRefGoogle Scholar
  3. 3.
    Leslie DL, Marcantonio ER, Zhang Y, et al. One-year health care costs associated with delirium in the elderly population. Arch Intern Med 2008; 168: 27–32PubMedCrossRefGoogle Scholar
  4. 4.
    Inouye SK, Rushing JT, Foreman MD, et al. Does delirium contribute to poor hospital outcomes? A three-site epidemiologic study. J Gen Intern Med 1998; 13: 234–42PubMedCrossRefGoogle Scholar
  5. 5.
    The HCUP Nationwide Inpatient Sample (NIS). Rockville (MD): Agency for Healthcare Research and Quality, 2004Google Scholar
  6. 6.
    Gardner W, Mulvey EP, Shaw EC. Regression analyses of counts and rates: Poisson, overdispersed Poisson, and negative binomial models. Psychol Bull 1995; 118: 392–404PubMedCrossRefGoogle Scholar
  7. 7.
    Poisson and negative binomial regressions. Lexington (KY): University of Kentucky, 2008 [online]. Available from URL: http://www.uky.edu/ComputingCenter/SSTARS/www/documentation/Contents_P_NB.htm [Accessed 2009 Nov6]
  8. 8.
    SAS annotated output negative binomial regression. Los Angeles (CA): UCLA Academic Technology Services, 2008 [online]: Available from URL: http://statistics.ats.ucla.edu/stat/sas/output/sas_negbin_output.htm [Accessed 2009 Nov 6]
  9. 9.
    Inouye S, van Dyck C, Alessi C, et al. Clarifying confusion: the Confusion Assessment Method. Ann Intern Med 1990; 113:941–8PubMedGoogle Scholar
  10. 10.
    Ely EW, Margolin R, Francis J, et al. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the intensive care unit (CAM_ICU). Crit Care Med 2001; 29: 1370–9PubMedCrossRefGoogle Scholar
  11. 11.
    Fletcher K, Hawkes P, Williams-Rosenthal S, et al. Using nurse practitioners to implement best practice care for the elderly during hospitalization: the NICHE journey at the University of Virginia Medical Center. Crit Care Nurs Clin North Am 2007; 19: 321–37PubMedCrossRefGoogle Scholar
  12. 12.
    Inouye SK, Bogardus Jr ST, Baker DI, et al. The Hospital Elder Life Program: a model of care to prevent cognitive and functional decline in older hospitalized patients. J Am Geriatr Soc 2000; 48: 1697–706PubMedGoogle Scholar
  13. 13.
    Pisani MA, Murphy TE, Van Ness PH, et al. Characteristics associated with delirium in older patients in a medical intensive care unit. Arch Intern Med 2007; 167: 1629–34PubMedCrossRefGoogle Scholar
  14. 14.
    Edlund A, Lundstrom M, Lundstrom G, et al. Clinical profile of delirium in patients treated for femoral neck fractures. Dement Geriatr Cogn Disord 1999; 10: 325–9PubMedCrossRefGoogle Scholar
  15. 15.
    Marcantonio ER, Flacker JM, Michaels M, et al. Delirium is independently associated with poor functional recovery after hip fracture. J Am Geriatr Soc 2000; 48: 618–24PubMedGoogle Scholar
  16. 16.
    Marcantonio ER, Flacker JM, Wright RJ, et al. Reducing delirium after hip fracture: a randomized trial. J Am Geriatr Soc 2001; 49: 516–22PubMedCrossRefGoogle Scholar
  17. 17.
    Kales HC, Blow FC, Bingham CR, et al. Race and inpatient psychiatric diagnoses among elderly veterans. Psychiatr Serv 2000; 51: 795–800PubMedCrossRefGoogle Scholar
  18. 18.
    Kales HC, Kamholz BA, Visnic SG, et al. Recorded delirium in a national sample of elderly inpatients: potential implications for recognition. J Geriatr Psychiatry Neurol 2003; 16: 32–8PubMedCrossRefGoogle Scholar
  19. 19.
    Liptzin B. What criteria should be used for the diagnosis of delirium? Dement Geriatr Cogn Disord 1999; 10: 364–7PubMedCrossRefGoogle Scholar
  20. 20.
    Inouye SK. The dilemma of delirium: clinical and research controversies regarding diagnosis and evaluation of delirium in hospitalized elderly medical patients. Am J Med 1994; 97: 278–88PubMedCrossRefGoogle Scholar
  21. 21.
    Cole M, McCusker J, Dendukuri N, et al. The prognostic significance of subsyndromal delirium in elderly medical inpatients. J Am Geriatr Soc 2003; 51: 754–60PubMedCrossRefGoogle Scholar
  22. 22.
    Fick D, Agostini J, Inouye S. Delirium superimposed on dementia: a systematic review. J Am Geriatr Soc 2002; 50: 1723–32PubMedCrossRefGoogle Scholar
  23. 23.
    Fleury MD, Stratton J, Tinga C, et al. A descriptive analysis of hospitalization due to acute gastrointestinal illness in Canada, 1995–2004. Can J Public Health 2008; 99: 489–93PubMedGoogle Scholar
  24. 24.
    Holstein J, Taright N, Lepage E, et al. Quality of medical database to valorize the DRG model by ISA cost indicators. Rev Epidemiol Sante Publique 2002; 50: 593–603PubMedGoogle Scholar
  25. 25.
    Humphries KH, Rankin JM, Carere RG, et al. Co-morbidity data in outcomes research: are clinical data derived from administrative databases a reliable alternative to chart review? J Clin Epidemiol 2000; 53: 343–9PubMedCrossRefGoogle Scholar
  26. 26.
    Franco K, Litaker D, Locala J, et al. The cost of delirium in the surgical patient. Psychosomatics 2001; 42: 68–73PubMedCrossRefGoogle Scholar
  27. 27.
    Saravay SM, Kaplowitz M, Kurek J, et al. How do delirium and dementia increase length of stay of elderly general medical inpatients? Psychosomatics 2004; 45: 235–42PubMedCrossRefGoogle Scholar
  28. 28.
    Zakriya K, Sieber FE, Christmas C, et al. Brief postoperative delirium in hip fracture patients affects functional outcome at three months. Anesth Analg 2004; 98: 1798–802PubMedCrossRefGoogle Scholar

Copyright information

© Adis Data Information BV 2010

Authors and Affiliations

  • Robert Y. Lin
    • 1
    • 2
  • Laura C. Heacock
    • 3
  • Joyce F. Fogel
    • 1
    • 2
  1. 1.Department of MedicineSt Vincent’s Hospital-Manhattan-SVCMCNew YorkUSA
  2. 2.Department of MedicineNew York Medical CollegeValhallaUSA
  3. 3.School of MedicineNew York Medical CollegeValhallaUSA

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