Higher DHA Omega-3 Status and Reduced Cognitive Decline in Elderly
Otsuka, R. et al., European J. of Clinical Nutrition, in press, 2014
National Center for Geriatrics and Gerontology, Aichi, Japan
The presence of high levels of DHA omega-3 fatty acid (docosahexaenoic acid n-3) in the cellular membranes of brain and nerve tissue are regarding as physiologically-essential for supporting optimal brain functioning. Dietary intakes of DHA are highly variable between countries and individuals within a given country due mainly to differences in fish/seafood consumption. The primary focus of this study was to determine if long-chain omega-3 fatty acids as DHA/EPA may possibly slow down the rate of cognitive deterioration with aging.
The present investigation was part of the Longitudinal Study of Aging wherein 232 males and 198 females aged 60-79 years were assessed for cognitive functioning by the MMSE (Mini-Mental State Examination). The MMSE (testing for orientation, attention, recall, etc) is a commonly-used screening test for dementia resulting in scores ranging from 0-30 points with a higher score indicating better cognitive performance. The average initial MMSE score of the subjects was 28. Upon enrollment in the study, blood samples were taken from the participants and the omega-3 status was assessed by measuring the levels of DHA and EPA in the blood serum. Those individuals who showed a decline in the MMSE by at least 4 points ten years later (8.3 % of the subjects) or a MMSE score equal to or below 23 (3.5 % of the subjects) were classified as having exhibited ‘cognitive decline’. Higher blood serum levels of DHA were associated with a significantly lower risk of cognitive decline whereas no such relationship was found with respect to EPA status. Those residing in the category of the top third with respect to DHA status in the blood had a 69 - 83 % lower risk of showing cognitive decline as compared to those in the bottom third for DHA status after adjusting for other confounding factors.
The present report from Japan is of relevance to a community study and publication by Dr. Morris and colleages in 2003 (Arch. Neurol., 60: 940-946). They followed and monitored 815 residents (aged 65-94 years) and found that those with higher intakes of fish and DHA (but not EPA) had a lower risk of developing Alzheimer disease. It is noted in the present study from Japan that the average subject had a substantial intake of 588 mg DHA/day. Current North American intakes are only approximately one-seventh this amount due to a relatively low consumption of fish/seafood.