Physical and Cognitive Activities Don't Affect AD Biomarkers

Pauline Anderson

June 16, 2015

Doing crossword puzzles, reading, and engaging in other cognitively stimulating activities may reduce the risk for Alzheimer`s disease (AD), but not through an effect on brain β-amyloid (Aβ) burden, glucose metabolism, or hippocampal volume, new research shows.

"These findings suggest that while a history of lifelong cognitive activity may support better cognitive performance, this relation is mediated by a mechanism independent of Aβ burden and markers of neurodegeneration (glucose metabolism and hippocampal volume) in cognitively normal older adults," the authors, led by Christopher M. Gidicsin, BA, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, conclude.

Furthermore, being physically active in the recent past, through activities such as walking or gardening, also didn't seem to relate to AD biomarkers in this study.

The findings shouldn't mean discouraging patients from engaging in physically and mentally stimulating activities because these activities offer many brain benefits, author Keith A. Johnson, MD, Harvard Medical School and Massachusetts General Hospital, said in a press release from the American Academy of Neurology. 

The results were published online June 10 in Neurology.

The analysis included 186 adults aged 65 to 90 years who were participating in the Harvard Aging Brain Study. Participants were cognitively intact; they had a Clinical Dementia Rating global score of 0 and scored 27 or higher on the Mini-Mental State Examination.

Participants underwent apolipoprotein E (APOE) genotyping. As well, they had positron emission tomography (PET) imaging with Pittsburgh compound B (PiB) to measure Aβ burden, PET imaging with F-fluorodeoxyglucose (FDG) to assess brain metabolism, and structural MRI to observe brain volume.

Participants also completed neuropsychological testing that encompassed multiple cognitive domains. Researchers created "cognitive factor scores," with variables organized into three primary factors: executive function, episodic memory, and processing speed.

The participants self-reported their history of cognitive activity. They subjectively rated their past and current level of participation in various activities, for example, reading, writing, going to the library, and playing games such as crossword puzzles.

To assess physical activity, participants completed questionnaires about how often and for how long in the previous 2 weeks they had engaged in six different exercises: walking, gardening or yard work, calisthenics or general exercise, bicycle riding, swimming or water exercise, and dancing.

For an objective measure of physical activity, participants wore a pedometer, which accurately measures step counts, for 7 days. This information was not available in previous research.

The study found no evidence of a protective effect of past or present cognitive activity, or recent physical activity, on any of the AD biomarkers, including PiB retention, FDG uptake, or hippocampal volume.

The analysis did find that greater past and current cognitive activity was associated with greater IQ and education, as well as better performance on neuropsychological tests. Physical activity was not related to cognitive testing performance. Greater self-reported recent physical activity was related to objective exercise monitoring.

The results, said the study authors, "align well" with other large studies that found a relationship between lifelong cognitive activity and current performance on neuropsychological testing, without a direct relationship between cognitive or physical activity and multiple AD biomarkers.

A limitation of the study was that measurement of lifelong cognitive and recent physical activity relied on a retrospective self-reported questionnaire, which may have participant bias. The findings might be further tested by using objective measures of cognitive and physical activity, said the authors.

The study was supported by the National Institute on Aging and the Alzheimer's Association. The authors have disclosed no relevant financial relationships.

Neurology. Published online June 10, 2015. Abstract

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