American Academy of Neurology (AAN) via Newswise – MINNEAPOLIS – A new study suggests that healthy older people who eat two or more servings of fish a week, including salmon, tuna and sardines, may have a lower risk later in life of developing vascular brain disease, a group of conditions that affect blood flow and blood vessels in the brain. The research is published in the November 3, 2021, online issue of Neurology®, the medical journal of the American Academy of Neurology. The study found that eating a diet rich in fish had the greatest protective effect on people younger than 75 years old.
“Our results are exciting because they show something as simple as eating two or more servings of fish each week is associated with fewer brain lesions and other markers of vascular brain damage, long before obvious signs of dementia appear,” said study author Cecilia Samieri, PhD, of the University of Bordeaux in France. “However, eating that much fish did not have a protective effect in people 75 years of age and older.”
The study looked at 1,623 people 65 and older, with an average age of 72, who did not have dementia, stroke or a history of cardiovascular disease. Brain scans were taken to look for three markers of vascular disease that are strong predictors of cognitive decline and dementia. They were white matter hyperintensities, which are small lesions on the brain; covert infarcts, or cavities in the brain; and enlarged perivascular spaces, which are fluid-filled spaces in brain tissue. By combining these three markers, researchers came up with a single measure of underlying vascular brain disease.
People filled out questionnaires about their diets, which included information about how frequently they ate fish. The entire group, on average, consumed fish two times per week, with 11% of the group eating fish less than once a week, 37% eating fish about once a week, 47% eating fish two or three times per week and 6% eating fish four or more times per week. Overall, 8% of participants had covert infarcts and 6% had severe dilated perivascular spaces. Of overall white matter volume, 2% was from hyperintensities.
Researchers found that among people who ate no fish, 31% had markers of severe underlying vascular brain disease, compared to 23% of those who ate three servings a week, and 18% of those who ate four or more servings of fish per week. This association between lower fish consumption and greater severity of markers of vascular brain disease was independent of any differences in brain volumes and other variables like age and sex.
When looking at age, researchers found stronger associations for younger people, but no association for people 75 and older. In the younger people between the ages of 65 and 69 years, for whom fish was most strongly associated with brain disease, consuming fish two or three times a week was roughly equivalent, in the opposite direction, to the effect of having high blood pressure. Consuming fish four or more times a week had double that effect.
“More research is needed to help us understand the mechanism of how eating fish may preserve brain vascular health, because diet is a factor people can modify to possibly decrease their risk of cognitive decline and even dementia later in life,” Samieri said.
The study does not prove that eating fish prevents dementia, it only shows an association between the two.
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