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Rate of Cognitive Decline in AD Is Associated with Mortality

A faster rate of cognitive decline portends earlier death.

Alzheimer disease (AD) is associated with increased mortality, but previous studies have produced widely divergent estimates of survival time, and little is known about the association between the rate of disease progression and survival time. Hui and colleagues examined the association between rate of cognitive decline and mortality in patients seen at one dementia clinic who had clinically diagnosed AD and a baseline Mini-Mental State Examination (MMSE) score of 11 or higher (thus, patients with late-stage disease were excluded). All patients underwent clinical evaluation at baseline and annual cognitive-function testing, which consisted of 18 cognitive tests. The study lasted 4 years.

Of the 354 patients who were seen for at least one evaluation after baseline, 242 survived and 112 died. The researchers divided the participants into quartiles of overall rate of cognitive decline (from least to most rapid), based on a composite of the cognitive tests. Compared with mortality in the quartile with the least rapid decline, mortality was more than threefold higher in the second quartile, more than fivefold higher in the third quartile, and more than eightfold higher in the fourth quartile.

Comment: Recent studies have reported that median survival time following the diagnosis of AD is considerably shorter (<4 years) than previously thought (Arch Neurol 2002; 59:1764). These new data are consistent with this view and add the important information that the rate of cognitive decline is an important predictor of mortality. As the authors point out, because the time from diagnosis to death is much shorter than once believed, the current emphasis on interventions that can prevent AD, delay its onset, or slow its progression is crucial. Of potential interest, but not reported in the article, is the cause of death for each of the deceased study participants. Additionally, information about the association between mortality and a commonly used mental status measure such as the MMSE could be valuable to clinicians and their patients.

— Paul R. Solomon, PhD

Dr. Solomon is Professor of Psychology, Williams College, Williamstown, MA.

Published in Journal Watch Neurology February 13, 2004

Citation(s):

Hui JS et al. Rate of cognitive decline and mortality in Alzheimer's disease. Neurology 2003 Nov 25; 61:1356-61.

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