|Terminal decline in cognitive function
Wilson RS, LA Beckett, JL Bienias, DA Evans and DA Bennett
Neurology. 2003. 60(11):1782-1787.
BACKGROUND: Impending death is thought to be associated with age-related cognitive decline, but this association has not been well studied. METHODS: Participants were 763 older Roman Catholic nuns, priests, and brothers without dementia at baseline. They completed an average of 5.6 annual evaluations (range 2 to 9), with >95% follow-up participation in survivors. Each evaluation included administration of 19 cognitive function tests from which previously established measures of global cognition (mean = 0.108, SD = 0.502) and specific cognitive functions were derived. In a series of change point random effects models, the average point before death when rate of cognitive decline changed was identified, and rates of cognitive decline before and after the optimal change point were estimated, controlling for the effects of age, sex, and education. RESULTS: There were 122 deaths during the observation period. Those who died had lower global cognitive function at baseline than survivors (by 0.103 unit; p = 0.03), and beginning about 43 months before death, their annual rate of global cognitive decline sharply accelerated from an annual loss of 0.026 to 0.173 unit, a more than sixfold increase. Results were comparable in analyses that controlled for baseline health and disability. Terminal cognitive decline was evident in nearly all of those who died, but at highly variable rates. Remarkably little cognitive decline was evident in survivors. Decline in episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability also greatly increased about 3 to 6 years prior to death. CONCLUSION: On average, cognitive decline sharply accelerates in the last years of life.