Delirium in older medical inpatients and subsequent cognitive and functional status: a prospective study

Background: Delirium in older hospital inpatients appears to be associated with various adverse outcomes. The limitations of previous research on this association have included small sample sizes, short follow-up periods and lack of consideration of important confounders or modifiers, such as severi ty of illness, co-morbidity and dementia. The objective of this study was t o determine the prognostic significance of delirium, with or without dement ia, for cognitive and functional status during the 12 months after hospital admission, independent of premorbid function, comorbidity, severity of ill ness and other potentially confounding variables. Methods: Patients 65 years of age and older who were admitted from the emer gency department to the medical services were screened for delirium during their first week in hospital. Two cohorts were enrolled: patients with prev alent or incident delirium and patients without delirium, but similar in ag e and cognitive impairment. The patients were followed up at 2, 6 and 12 mo nths after hospital admission. Analyses were conducted for 4 patient groups : 56 with delirium, 53 with dementia, 164 with both conditions and 42 with neither. Baseline i measures included delirium (Confusion Assessment Method ), dementia (Informant Questionnaire on Cognitive Decline in the Elderly), physical function (Barthel Index [BI] and premorbid instrumental activities of daily living, IADL), the Mini-Mental State Examination (MMSE), comorbid ity, and physiologic and clinical severity of illness. Outcome variables me asured at follow-up were the MMSE, Barthel Index, IADL and admission to a l ong-term care facility. Results: After adjustment for covariates, the mean differences in MMSE scor es at if follow-up between patients with and without delirium were -4.99 (9 5% confidence interval [CI] -7.17 to -2.81) for patients with dementia and -3.36 (95% Cl -6.15 to -0.58) for those without dementia. At 12 months, the adjusted mean differences in the BI were -16.45 (95% CI -27.42 to -5.50) a nd -13.89 (95% Ci -28.39 to 0.61) for patients with and without dementia re spectively. Patients with both delirium and dementia were more likely to be admitted to long-term care than those with neither condition (adjusted odd s ratio 3.18, 95% CI 1.19 to 8.49). Dementia but not delirium predicted wor se IADL scores at follow-up. Unadjusted analyses yielded similar results. Interpretation: For older patients with and without dementia, delirium is a n independent predictor of sustained poor cognitive and functional status d uring the year after a medical admission to hospital.