Which Comes First in Alzheimer’s: Cognitive or Functional Decline?

Functional decline is a normal part of aging. Many older individuals experience loss of functionality in certain areas of life as they age. These losses could be due to physical impairment, illness, mental health, or just the natural aging process. For some, functional impairment is the result of cognitive decline.

Some cognitive decline is common with advanced age, but not for all people. Those who develop dementia or Alzheimer’s (AD) may realize mild cognitive impairment (MCI) more often than those who do not eventually go on to develop dementia. MCI and significant cognitive impairment can have a large impact on functionality. But until now, it has been unclear whether functionality is a predictor of cognitive impairment or whether cognitive impairment predicts functional impairment in dementia and AD.

To clarify this relationship, Laura B. Zahodne of the Cognitive Neuroscience Division and the Department of Neurology at the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain in New York recently led an examination using data from two existing studies. The longitudinal data included assessments from 3,443 adults without dementia and 517 with AD. Of those without dementia at study onset, 612 eventually developed cognitive impairment that was classified as dementia. Zahodne looked specifically at language and memory tests for signs of cognitive decline and based functional performance on self or caregiver reports.

The results revealed that in every case, cognitive tests were more predictive of functionality than functional reports were of cognitive ability. In other words, the cognitive results taken at the beginning of the study and over several subsequent assessments accurately predicted functional decline in all of the participants the majority of the time. In contrast, the functional reports were less accurate at predicting future cognitive impairment.

Zahodne believes that these unique findings show the importance of identifying specific cognitive weaknesses in elderly individuals, especially those with any indicators of functional impairment. She added, “Together, these results support the importance of assessing memory and language with tests that require greater executive demands to detect the earliest deficits of AD.”

Reference:
Zahodne, L.B., Manly, J.J., MacKay-Brandt, A., Stern, Y. (2013). Cognitive declines precede and predict functional declines in aging and Alzheimer’s disease. PLoS ONE 8(9): e73645. doi:10.1371/journal.pone.0073645

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  • jameson

    jameson

    September 20th, 2013 at 3:51 AM

    good for those in the research field to have and use when looking at patients and predicting who may be the most likely to develop this debilitating disease

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