While the study, which was led by researchers from Oregon Health and Science University (OHSU), found no statistically significant benefit for older adults in general, a reduction was observed in the breakdown of nerve cells in the brains of participants who carried the APOE*E4 gene.
This genetic variant is associated with an increased risk of developing Alzheimer’s; globally, between 15 and 25% of people have the allele, while 2 to 5% carry two copies.
“Although omega-3 treatment failed to reach significant reduction in white matter lesion progression and neuronal integrity breakdown among all participants at risk for dementia, the findings suggest that APOE*E4 carriers may benefit from omega-3 treatment,” the study authors wrote.
High omega-3 levels previously linked to lower Alzheimer's risk
Previous research has observed a link between high levels of omega-3 in the blood and a lower risk of dementia and Alzheimer's disease, with a stronger association found in people aged over 60 years.
The OHSU study, which was published in the journal JAMA Network Open, enlisted 102 people aged 75-plus who had relatively low blood levels of omega-3 fatty acids, which are found in foods like fish and flaxseed, as well as dietary supplements, such as fish oil.
Participants had relatively high levels of white matter lesions but were otherwise healthy, with no dementia. Magnetic resonance imaging (MRI) was carried out at enrolment and again at the conclusion of the three-year study to assess changes in these white matter lesions, which may inhibit the delivery of nutrients through blood vessels to the brain, raising the risk of developing dementia later in life.
Half of the group took daily omega 3-enriched fish oil supplements; the others took a soybean-based placebo.
A slight reduction in the progression of white matter lesions was observed by the end of the study period; however, this was not enough to be statistically significant between the two groups.
Among APOE*E4 carriers, however, researchers measured a dramatic reduction in the breakdown of brain cell integrity just one year after treatment, compared with placebo.
They concluded: “The significant reduction in neuronal integrity breakdown among APOE*E4 carriers suggests that the effects of omega-3 may be amplified for these individuals. These results will enable improved study design and sample size calculations for future efforts of a relatively cheap, safe, and well-tolerated therapy for primary and secondary dementia prevention.”
Co-author Gene Bowman, director of clinical trials and instructor of neurology at the McCance Center for Brain Health, Massachusetts General Hospital, and Harvard Medical School, said: “This is the first dementia prevention trial to use modern prevention tools, such as a blood test and brain scan, to identify not only people at high risk for dementia, but also those well suited to receive a specific nutritional intervention.
“The fact that neuronal integrity breakdown was slowed in people randomised to omega-3 treatment who are also at high risk for Alzheimer’s disease is remarkable, and warrants a larger clinical trial in more diverse populations in the future.”