Eating seafood or other foods rich in omega-3 fatty acids at least once a week may help protect older adults from age-related memory loss and declines in some thinking abilities, according to researchers from Rush University Medical Center and Wageningen University in the Netherlands.
The findings, published in the May 4 online issue of the journal Neurology, are based on a long-term follow-up of older adults and were supported by the National Institute on Aging and the Judith Zwartz Foundation.
Weekly seafood linked to slower cognitive decline
In this study, people who reported eating seafood fewer than once per week showed faster declines in some cognitive functions compared with those who ate seafood at least once weekly. Martha Clare Morris, ScD, a nutritional epidemiologist at Rush and the study’s senior author, notes that while some cognitive decline is a normal part of aging, dietary choices—such as including seafood in the diet—may help slow that process.
Study group and methods
The researchers followed 915 participants with an average age of 81.4 years for an average of five years. At the start of the study none of the participants had dementia. Participants were drawn from the Rush Memory and Aging Project, which includes residents across more than 40 retirement communities and senior housing units in northern Illinois, along with volunteers recruited through community organizations.
Each participant completed annual cognitive testing that measured five domains of brain function: episodic memory, working memory, semantic memory, visuospatial ability, and perceptual speed. The study also used yearly food frequency questionnaires to track dietary habits and estimate seafood and omega-3 fatty acid intake.
What counted as seafood in the study
The dietary questionnaire classified seafood into four categories: tuna sandwiches; fish sticks, fish cakes, or fish sandwiches; fresh fish served as a main dish; and shellfish such as shrimp, lobster, and crab. Participants were grouped into those who ate at least one seafood meal per week and those who ate seafood less than once weekly. On average, the higher-intake group consumed about two seafood meals per week, while the lower-intake group averaged about half a meal weekly.
Specific cognitive benefits observed
The study found that higher seafood consumption was associated with slower decline in two cognitive areas: semantic memory (the ability to remember verbal information and facts) and perceptual speed (the ability to quickly compare letters, shapes, and patterns). No significant protective association was observed for episodic memory (recall of personal events), working memory (short-term mental processing), or visuospatial ability (understanding spatial relationships).
These associations remained after the researchers adjusted for other factors known to influence cognition, including education level, physical activity, smoking status, and engagement in mentally stimulating activities.
APOE-ε4 carriers may benefit more
The protective relationship between seafood intake and cognitive decline appeared stronger among people who carry the APOE-ε4 gene variant. APOE is a gene involved in cholesterol transport to neurons, and the ε4 variant is known to increase risk for Alzheimer’s disease. About one in five people carry the APOE-ε4 allele, although carrying the gene does not guarantee development of Alzheimer’s disease. In this study, APOE-ε4 carriers who consumed seafood weekly—or who had moderate to high dietary intake of long-chain omega-3 fatty acids—showed slower cognitive decline across multiple domains; these associations were not observed in noncarriers.
Funding: This study received support from the NIH/National Institute on Aging and the Judith Zwartz Foundation.
Source: Rush University Medical Center (Nancy DiFiore)
Original research: Ondine van de Rest, Yamin Wang, Lisa L. Barnes, Christine Tangney, David A. Bennett, and Martha Clare Morris. “APOE ε4 and the associations of seafood and long-chain omega-3 fatty acids with cognitive decline.” Neurology, published online May 4, 2016. doi:10.1212/WNL.0000000000002719
Study abstract overview
Objective: To examine how consumption of seafood and long-chain n-3 (omega-3) fatty acids relates to changes in five cognitive domains over an average 4.9-year follow-up period.
Methods: The analysis included 915 participants (mean age 81.4 years, 25% men) from the Rush Memory and Aging Project who had completed at least one follow-up cognitive assessment and provided dietary information via a semi-quantitative food frequency questionnaire. Cognitive performance was measured using 19 tests that combined into scores for global cognition and five specific domains. Mixed-effects models adjusted for numerous risk factors were used to evaluate associations.
Results: Weekly seafood consumption was associated with slower decline in semantic memory and perceptual speed after adjusting for age, sex, education, cognitive and physical activity, alcohol use, smoking, and total energy intake. Secondary analyses indicated that APOE-ε4 carriers experienced slower decline in global cognition and several cognitive domains with weekly seafood intake and moderate-to-high long-chain omega-3 intake from food; these relationships were not observed in noncarriers. Higher intake of alpha-linolenic acid was also linked with slower global decline but only among APOE-ε4 carriers.
Conclusions: Eating at least one seafood meal per week and consuming long-chain omega-3 fatty acids through food were associated with protection against decline in certain cognitive domains among older adults. The role of APOE-ε4 in modifying these associations deserves further research.