Cognitive decline after hospitalization in a community population of older persons

Abstract

Objective: To test the hypothesis that hospitalization in old age is associated with subsequent cognitive decline.

Methods: As part of a longitudinal population-based cohort study, 1,870 older residents of an urban community were interviewed at 3-year intervals for up to 12 years. The interview included a set of brief cognitive tests from which measures of global cognition, episodic memory, and executive function were derived. Information about hospitalization during the observation period was obtained from Medicare records.

Results: During a mean of 9.3 years, 1,335 of 1,870 persons (71.4%) were hospitalized at least once. In a mixed-effects model adjusted for age, sex, race, and education, the global cognitive score declined a mean of 0.031 unit per year before the first hospitalization compared with 0.075 unit per year thereafter, a more than 2.4-fold increase. The posthospital acceleration in cognitive decline was also evident on measures of episodic memory (3.3-fold increase) and executive function (1.7-fold increase). The rate of cognitive decline after hospitalization was not related to the level of cognitive function at study entry (r = 0.01, p = 0.88) but was moderately correlated with rate of cognitive decline before hospitalization (r = 0.55, p = 0.021). More severe illness, longer hospital stay, and older age were each associated with faster cognitive decline after hospitalization but did not eliminate the effect of hospitalization.

Conclusion: In old age, cognitive functioning tends to decline substantially after hospitalization even after controlling for illness severity and prehospital cognitive decline.

Figure 1. Typical path of posthospital change in global cognitive function

Predicted 10-year paths of change in composite measure of global cognition for typical participants hospitalized in year 4 (red line) or not hospitalized (black line) from a mixed-effects model adjusted for age, sex, race, and education.

Figure 2. Individual differences in posthospital change in global cognitive function

Person-specific paths of change in composite measure of global cognition estimated for a 7.5% random sample of participants from a mixed-effects model adjusted for age, sex, race, and education.

Figure 3. Modification of posthospital change in global cognitive function

Predicted 10-year paths of change in composite measure of global cognition for typical participants hospitalized in year 4 with a Charlson score of 0 (black line) vs 2 (red line) (A) or a hospital stay of 2 days (black line) vs 13 days (red line) (B), from mixed-effects models adjusted for age, sex, race, and education.