Eating fish every week linked to less dementia

Consumption of baked or broiled fish on a weekly basis improved brain health and significantly reduced the risk of mild cognitive impairment and Alzheimer’s disease in a 20-year longitudinal study of older adults.

Fish consumption improved brain volume in the frontal lobes, temporal lobes (including the hippocampus), and posterior cingulate gyrus, as shown on high-resolution, three-dimensional volumetric magnetic resonance imaging (MRI). “That’s important because these are areas of the brain that are responsible for memory and learning and are severely affected by Alzheimer’s disease,” the University of Pittsburgh said.

Colleagues analyzed data collected at three time points from the ongoing Cardiovascular Health Study- Cognition Study. In 1989-1990, 260 subjects (mean age 71 years) completed standardized diet questionnaires. In 1998-1999, these individuals (mean age 78 years) underwent volumetric MRI.

Analysis of clinical conversion to mild cognitive impairment (MCI) or Alzheimer’s disease (AD) in 2002 among study participants (mean age 82 years) found that individuals with larger brain volumes as a result of weekly baked or broiled fish consumption had a greatly reduced incidence of MCI or AD, compared with those who did not eat fish regularly.

Clinical conversion rates to MCI or AD were 30.8% for non-fish eaters, compared with 8% for individuals whose  brains  benefited partially from fish consumption (as shown on volumetric MRI), and 3.2% for individuals whose brains benefited fully from fish consumption.

These findings indicate “a large reduction in the risk for developing AD or MCI as a result of consuming baked or broiled fish.”

The benefits of fish intake persisted even after accounting for such potential confounding variables as age, gender, head size, and cerebrovascular disease.

Study participants who were not fish eaters and who showed atrophy in the hippocampus — the region most frequently affected by AD — had a 47% incidence of MCI or AD, compared with only 28% of fish eaters with larger hippocampal volumes.

Mean scores on cognitive tests of working memory were significantly higher (P less than .05) in individuals who ate fish weekly compared with those who did not. The improvement remained even after accounting for potential confounders such as age, gender, and education.

The researchers also looked at cognitive test scores and brain volumes and found a relationship between larger frontal lobe volumes in fish eaters and higher working memory test scores. ‘’This makes a lot of sense, because the frontal lobes are responsible for working memory function.”

The reduced risk of MCI and AD among fish eaters in this study probably stems from the protective benefits of omega-3 fatty acids. Omega-3 fatty acids are believed to increase blood flow to the brain, act as antioxidants and anti-inflammatories, and prevent the accumulation of the amyloid plaques characteristics of AD.