Eating Fish May Reduce the Risk for Subclinical Brain Abnormalities

Allison Gandey

August 07, 2008

August 7, 2008 — Dietary intake of tuna and other fish appear to lower the prevalence of subclinical infarcts and white-matter abnormalities, report researchers.

In the August 5 issue of Neurology, investigators show that a modest intake of fish among older adults was associated with fewer brain abnormalities on magnetic resonance imaging (MRI).

"One of the differences in this study is that we looked at various types of fish," second author David Siscovick, MD, from the University of Washington, in Seattle, said during an interview. "We also found that broiled and baked fish appeared to be beneficial, while fried fish was not."

The findings add to prior evidence suggesting fish with higher eicosapentaenoic and docosahexaenoic acid content appear to have clinically important health benefits. The American Heart Association advises that people eat fish at least 2 times a week. The recommendation promotes fatty fish such as mackerel, herring, tuna, and salmon — all high in omega-3 fatty acids.

"Our data are consistent with this recommendation," Dr. Siscovick told Medscape Neurology & Neurosurgery. He urges clinicians to discuss with patients the type of fish and how it is prepared. "Telling people to eat more fish without counseling them on these details may not have the same impact," he advised.

In the current study, investigators led by Jyrki Virtanen, PhD, from the University of Kuopio, in Finland, looked at 3660 participants aged 65 years and older. Patients were part of the population-based Cardiovascular Health Study, and all participants underwent MRI at baseline. Five years later, just over 2300 had a second scan.

Neuroradiologists assessed MRIs in a standardized and blinded manner. The researchers used food frequency questionnaires to assess diet, and participants with known cerebrovascular disease were excluded from the analysis.

Consuming Fish 3 or More Times a Week Beneficial

After adjusting for multiple risk factors, the researchers found that the risk of having 1 or more prevalent subclinical infarcts was lower among individuals who consumed tuna and other fish 3 or more times a week compared with those who ate fish less than once a month (relative risk, 0.74; 95% CI, 0.54 – 1.01; P = .06; P for trend = .03).

They found that fish consumption was also associated with trends toward lower incidence of subclinical infarcts. And fish was linked to better white-matter grade, but not with sulcal and ventricular grades — markers of brain atrophy. Investigators observed no significant associations between fried-fish consumption and any subclinical brain abnormalities.

The researchers point to several strengths of their study, such as the population-based recruitment, the large numbers of participants enrolled, and the extensive standardized examinations of other risk factors. They also prospectively collected data on dietary intake and MRI findings.

But the study also had several limitations. They note that although interreader reliabilities of white-matter and ventricular grades are good, estimates of sulcal grade tend to have greater interreader variability. The researchers also point out that the observed associations could be related to other differences related to fish consumption, such as a healthier lifestyle in general. "However," they write, "we adjusted for a variety of other risk factors and lifestyle habits."

The investigators recommend that randomized trials of fish or fish-oil intake be conducted to assess the potential to reduce subclinical ischemic events. Such studies, they suggest, would be feasible and important given the high incidence of such events in older adults.

The researchers have disclosed no relevant financial relationships.

Neurology. 2008;71:439-446. Abstract

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