Recoverable cognitive dysfunction at hospital admission in older persons during acute illness

Abstract

Background: While acute illness and hospitalization represent pivotal events for older persons, their contribution to recoverable cognitive dysfunction (RCD) has not been well examined.

Objective: Our goals were to estimate the frequency and degree of RCD in an older hospitalized cohort; to examine the relationship of RCD with delirium and dementia; and to determine 1-year cognitive outcomes.

Design: Prospective cohort study.

Participants: Four hundred and sixty patients aged > or =70 years drawn from consecutive admissions to an academic hospital.

Measurements: Patients underwent interviews daily during hospitalization and at 1 year. The primary outcome was RCD, defined as an admission Mini-Mental State Examination (MMSE) score that improved by 3 or more points by discharge.

Results: Recoverable cognitive dysfunction occurred in 179 of 460 (39%) patients, with MMSE impairment at baseline ranging from 3 to 13 points (median=5.0 points). The majority of cases were not characteristic of either delirium or dementia, as 144 of 179 (80%) cases did not meet criteria for delirium, and 133 of 164 (81%) cases did not meet criteria for dementia at baseline. In multivariable analysis controlling for baseline MMSE level, 3 factors were predictive of RCD: higher educational level, preadmission functional impairment, and higher illness severity. At 1 year, further improvement in MMSE score occurred in 38 of 92 (41%) patients with RCD. Recoverable cognitive dysfunction was independently predictive of 1-year mortality with an adjusted odds ratio of 1.82 (95% confidence interval [95% CI] 1.03 to 3.20).

Conclusions: Acute illness is accompanied by a high rate of RCD that is neither characteristic of delirium or dementia. Our observations underscore the reversible nature of this cognitive dysfunction with continued improvement over the ensuing year, and highlight the potential clinical implications of this under-recognized phenomenon.

FIGURE 1

Degree of recoverable cognitive dysfunction (RCD) at hospital admission (N = 179). This figure demonstrates the number and percent of patients with reduction in MMSE scores at hospital admission, compared with their highest MMSE score at any time during hospitalization, among RCD patients only. For this study, recoverable cognitive dysfunction was defined as an admission MMSE score that improved 3 or more points by the time of hospital discharge. The amount of reduction in MMSE scores ranged from 3 to 13 points, with a median of 5.0 points. The number of patients is indicated above each bar. MMSE, Mini-Mental State Examination.