Lower blood levels of omega-3 fatty acids are associated with smaller brain volumes and worse cognitive performance, researchers reported.
The structural findings suggest that people with low levels of the nutrients -- found mainly in fish -- have brains that appear to have aged faster than normal, according to Zaldy Tan, MD, of the University of California Los Angeles, and colleagues.
And the cognitive findings suggest they also are likely to lose some of their ability to think abstractly and remember some things, Tan and colleagues reported in the Feb. 28 issue of Neurology.
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Lower blood levels of omega-3 fatty acids are "associated with markers of accelerated structural and cognitive aging," the researchers concluded.
For instance, Tan said in a statement, the lower brain volumes "were equivalent to about two years of structural brain aging."
But he and colleagues cautioned that the findings are based a snapshot study, so there are no measurements of rates of change of either brain volume or cognitive performance.
The two omega-3 fatty acids under study were docosahexaenoic and eicosapentaenoic acid (DHA and EPA, respectively), which have been related to a reduced risk for dementia, the researchers noted.
But there has been no research on any links between the acids and subclinical markers of future dementia, they added.
To help fill the gap, they turned to participants in the long-running Framingham Offspring cohort who had physical examinations from March, 2005 to January, 2008 (including blood sampling to measure omega-3 levels), followed by brain imaging and a neuropsychological assessment.
All told, the study group included 1,575 people with an average age of 67, who were free of dementia at the time.
The researchers analyzed red blood cell levels of DHA and the so-called omega-3 index, defined as the combination of DHA and EPA, seeking associations between omega-3 levels, imaging findings, and results on cognitive tests involving verbal memory, visual memory, executive function, and abstract thinking.
Participants with DHA in the lowest quartile had significantly lower total brain and greater white matter hyperintensity volumes. Lower DHA levels also were associated with poorer scores on tests of visual memory, executive function and abstract thinking. There was no association between levels of DHA or omega-3 index, and verbal memory.
Tan and colleagues cautioned that the participants were mainly Caucasian, so it is not clear how well the results apply to other groups.