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AAIC: Aerobic exercise proves beneficial for mild cognitive impairment
Key clinical point: Regular aerobic exercise boosted cognition and blood flow to the brain, and improved cerebrospinal biomarkers associated with...
Neither a physical activity program nor omega-3 long-chain polyunsaturated fatty acid supplements improved cognitive function in two separate studies of high-risk elderly patients reported online Aug. 25 in JAMA.
Both studies were secondary analyses of large randomized clinical trials. Their findings contradict the results of many epidemiologic and observational studies attesting to the cognitive benefits of both lifestyle interventions.
The first study involved 1,635 sedentary men and women aged 70-89 years who had lower-extremity functional limitations and were participating in the LIFE (Lifestyle Interventions and Independence for Elders) trial at eight U.S. medical centers. These participants were randomly assigned to either a physical activity intervention (818 study subjects) or a health education program (817 control subjects) and were assessed with a comprehensive battery of neuropsychological tests every 6 months for 2 years, according to Dr. Kaycee M. Sink of the Sticht Center on Aging at Wake Forest University, Winston-Salem, N.C., and her associates.
The intervention comprised two weekly clinic visits plus three to four weekly home sessions focused on strength, flexibility, and balance training, as well as walking. The control situation consisted of weekly 60- to 90-minute workshops on topics such as travel safety, preventive services, legal and financial issues, and nutrition. As expected, the intervention group achieved a higher level of moderate to vigorous physical activity throughout follow-up (mean increase of 130.4 minutes/week), compared with the control group (mean increase of 30.5 minutes/week).
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Omega-3 supplements did little to improve cognitive function in high-risk elderly patients.
However, after 2 years, there were no significant differences between the two groups in either global cognitive scores or in individual scores on numerous measures of psychomotor speed, attention, concentration, working memory, word list learning, word recall, visuospatial function, figural memory, language, or executive function. There also were no differences in the rates of mild cognitive impairment, dementia, or both combined: 13.2% of the intervention group and 12.1% of the control group developed MCI or dementia by 2 years, a nonsignificant difference, the investigators said (JAMA. 2015;314[8]:781-90).
It is possible that the level of physical activity in this intervention may not have been sufficient to produce changes in cognitive measures, or that cognitive function improved in the short term but dissipated by the end of the second year of follow-up. Alternatively, the study population on the whole was well educated (more than two-thirds attended college), and high cognitive reserve may have protected against cognitive decline in both groups. It is also possible that the health education intervention provided enough cognitive and social stimulation to preserve cognitive function in the control group, Dr. Sink and her associates said.
The second report was an ancillary study of AREDS2 (Age-Related Eye Disease Study 2), a randomized clinical trial that assessed various dietary supplements’ effect on age-related macular degeneration and cataracts. This trial’s median 5-year follow-up of older patients (mean age, 73 years) gave researchers a chance to examine any possible cognitive benefits of treatment with omega-3 long-chain polyunsaturated fatty acids – docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and/or lutein/zeaxanthin, said Dr. Emily Y. Chew of the division of epidemiology and clinical applications at the National Eye Institute and National Institutes of Health, and her associates (JAMA 2015;314[8]:791-801).
The 3,073 study participants were assessed using eight tests of cognitive function after first “passing” a hearing handicap inventory, a depression scale, and the Telephone Interview of Cognitive Status to assure their functional status. The eight tests examined immediate and delayed recall, language, executive function, word fluency, memory, attention, and processing speed.
At 5-year follow-up, there were no significant differences between the two study groups in either a global assessment of cognitive function or in any of the individual component assessments. The yearly change in scores on the composite measure was –0.19 with supplements and –0.18 without supplements, a nonsignificant difference on their scale from –22 to +17, Dr. Chew and her associates said.
It is not yet known why abundant observational data support the use of these supplements to improve cognitive function but most randomized clinical trials, like this one, fail to show such beneficial effects. “It is possible that these supplements were started too late in the aging process” to exert an effect, or that a 5-year duration of treatment was insufficient, they noted.
