BEHAVIORAL INTERVENTIONS TO PREVENT, DELAY, OR SLOW ALZHEIMER’S DISEASE, MILD COGNITIVE IMPAIRMENT, OR AGE-RELATED COGNITIVE DECLINE

Abstract

Assess evidence for behavioral interventions aimed at preventing or delaying onset of age-related cognitive decline, mild cognitive impairment (MCI), or clinical Alzheimer's-type dementia (CATD). We searched Medline, PsycINFO, Embase, and Cochrane Central Register of Controlled Trials through September, 2016, supplemented with hand-searching. Two investigators screened abstracts and full-text articles of identified references. Eligible studies included randomized and nonrandomized controlled trials and quasi-experimental observational studies enrolling people with normal cognition and/or MCI. We extracted data, assessed risk of bias, summarized results for studies without high risk of bias, and evaluated strength of evidence for studies with sufficient sample size. Cognitive outcomes were grouped into domains to facilitate analysis. We identified 170 eligible studies over 6 classes of interventions: cognitive training, physical activity, nutraceuticals, diet, multimodal interventions, and vitamins. We found no high-strength evidence for the effectiveness of any intervention to delay or prevent age-related cognitive decline, MCI, and/or CATD. Moderate-strength evidence shows cognitive training in adults with presumed normal cognition improves performance in the cognitive domain trained (memory, reasoning, or processing speed), but not transfer of benefits to other cognitive areas and little evidence for benefit beyond 2 years; evidence for effect on CATD is weak. Moderate-strength evidence showed no benefit for Vitamin E in women and B12 plus folic acid for executive/attention/processing speed. Physical activity interventions show no consistent benefit in preventing cognitive decline, but the proportion of results showing benefit were unlikely to be explained solely by chance, providing a signal of a possible relationship. A few other interventions showed at least one positive finding for a specific outcome, some reaching low strength of evidence, but these were more than offset by findings of no effect for other outcomes. We found no eligible studies for depression treatment or smoking cessation. Overall, evidence for is weak. Future research should address wide-spread methodological problems, including use of consistent cognitive outcome measures, longer follow-ups, and recognizing that attrition is a major problem in longer studies. More work is needed to understand the relationship between intermediate outcomes like cognitive test results and the onset of MCI and dementia.