Cognitive activity and the cognitive morbidity of Alzheimer disease

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New research shows that mentally stimulating activities such as crossword puzzles, reading and listening to the radio may, at first, slow the decline of thinking skills but speed up dementia later in old age. The research is published in the September 1, 2010, online issue of Neurology®, the medical journal of the American Academy of Neurology.

“Our results suggest that the benefit of delaying the initial signs of cognitive decline may come at the cost of more rapid dementia progression later on, but the question is why does this happen?” said study author Robert S. Wilson, PhD, neuropsychologist, Rush Alzheimer's Disease Center, Rush University Medical Center.

According to Wilson, mentally stimulating activities may somehow enhance the brain’s ability to function relatively normally despite the buildup of lesions in the brain associated with dementia. However, once they are diagnosed with dementia, people who have a more mentally active lifestyle are likely to have more brain changes related to dementia compared to those without a lot of mental activity. As a result, those with more mentally active lifestyles may experience a faster rate of decline once dementia begins.

Wilson noted that mental activities compress the time period that a person spends with dementia, delaying its start and then speeding up its progress. “This reduces the overall amount of time that a person may suffer from dementia,” he said.

For the study, researchers evaluated the mental activities of 1,157 people age 65 or older who did not have dementia at the start of the nearly 12-year study. People answered questions about how often they participated in mental activities such as listening to the radio, watching television, reading, playing games and going to a museum; for this five-point cognitive activity scale, the more points scored, the more often people participated in mentally stimulating exercises.

During the next six years, the study found that the rate of cognitive decline in people without cognitive impairment was reduced by 52 percent for each point on the cognitive activity scale. For people with Alzheimer’s disease, the average rate of decline per year increased by 42 percent for each point on the cognitive activity scale.

The study was supported by the National Institute on Aging and the National Institute of Environmental Health Sciences.

The American Academy of Neurology, an association of more than 22,000 neurologists and neuroscience professionals, is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer’s disease, epilepsy, Parkinson’s disease, and multiple sclerosis.

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http://www.neurology.org/cgi/content/abstract/WNL.0b013e3181f25b5ev1

R. S. Wilson PhD*, L. L. Barnes PhD, N. T. Aggarwal MD, P. A. Boyle PhD, L. E. Hebert ScD, C. F. Mendes de Leon PhD, and D. A. Evans MD. Cognitive activity and the cognitive morbidity of Alzheimer disease. Neurology 2010, doi:10.1212/WNL.0b013e3181f25b5e

Objective: To test the hypothesis that frequent cognitive activity predicts slower cognitive decline before dementia onset in Alzheimer disease (AD) and faster decline thereafter.

Methods: As part of a longitudinal cohort study, older residents of a geographically defined population were assessed at 3-year intervals with brief cognitive performance tests from which a composite measure of global cognition was derived. After each wave of testing, a subset was sampled for clinical evaluation. The present analyses are based on 1,157 participants. They were free of dementia at study enrollment at which time they rated frequency of participation in common cognitively stimulating activities from which a previously validated summary measure was derived. They were sampled for clinical evaluation a mean of 5.6 years after enrollment and subsequently followed a mean of 5.7 years with brief cognitive performance testing at 3-year intervals.

Results: On clinical evaluation, 614 people had no cognitive impairment, 395 had mild cognitive impairment, and 148 had AD. During follow-up, the annual rate of global cognitive decline in persons without cognitive impairment was reduced by 52% (estimate = 0.029, SE = 0.010, p = 0.003) for each additional point on the cognitive activity scale. In the mild cognitive impairment group, cognitive decline rate was unrelated to cognitive activity (estimate = -0.019, SE = 0.018, p = 0.300). In AD, the mean rate of decline per year increased by 42% (estimate = 0.075, SE = 0.021, p < 0.001) for each point on the cognitive activity scale.

Conclusion: Mentally stimulating activity in old age appears to compress the cognitive morbidity associated with AD by slowing cognitive decline before dementia onset and hastening it thereafter.

From the Rush Alzheimer's Disease Center (R.S.W., L.L.B., N.T.A., P.A.B.) and Rush Institute for Healthy Aging (L.E.H., C.F.M.d.L., D.A.E.) and Departments of Neurological Sciences (R.S.W., L.L.B., N.T.A., D.A.E.), Behavioral Sciences (R.S.W., L.L.B., P.A.B.), and Internal Medicine (L.E.H., C.F.M.d.L., D.A.E.), Rush University Medical Center, Chicago, IL.

* To whom correspondence should be addressed. E-mail: rwilson@rush.edu.