Abstract
Objective
To determine the impact of diet quality interventions on neurocognitive decline in older adults.
Design
Four databases were searched (Medline, EMBASE, CENTRAL and PsycINFO) for randomised controlled trials involving diet quality interventions and cognitive outcomes in older adults. Study quality was assessed using the Cochrane Risk of Bias tool. Outcomes selected for meta-analysis were memory and executive function, for which standardised mean differences (SMD) were calculated. Subgroup and sensitivity analyses were undertaken to explore causes of heterogeneity. Additional outcomes of global cognitive function, incident dementia, attention, language/verbal fluency, and processing speed were narratively synthesised.
Results
Twelve studies were included, investigating the Mediterranean, Dietary Approaches to Stop Hypertension and Nordic diets. Risk of bias varied across studies. Dietary intervention had a significant effect on memory (SMD: 0.98; 95% CI: 0.39, 1.57; p = 0.001) and executive function (SMD: 2.02; 95% CI: 1.04, 3.01; p < 0.00001), although neither outcome was significant in sensitivity analyses. Heterogeneity was high (I2 = 99%) prior to sensitivity analyses and low (I2 = 0%) after. Results for narratively synthesised cognitive measures were inconsistent with no clear direction of effect.
Conclusion
The current body of evidence would suggest the effect of dietary intervention on neurocognitive decline in older adults is unclear given the considerable heterogeneity and bias present across studies. These findings should be interpreted with consideration to the limited number of studies that could be included and the large variation in study designs. Further randomised controlled trials with harmonised cognitive outcomes and assessments are needed to clarify direction of effect.
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All authors have given final approval of the version to be published. LMcB contributed substantially to data collection, processing and interpretation; writing the first draft of the manuscript and revising it critically; SO’R: Substantial contribution to conception and design, processing and interpretation of data; writing the article and revising it critically for important intellectual content. SO’R is the guarantor for the work and the conduction of the study, including the decision to publish the work.
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McBean, L., O’Reilly, S. Diet quality interventions to prevent neurocognitive decline: a systematic review and meta-analysis. Eur J Clin Nutr 76, 1060–1072 (2022). https://doi.org/10.1038/s41430-021-01032-y
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DOI: https://doi.org/10.1038/s41430-021-01032-y