Higher dietary intake of DHA has been associated with better cognitive performance in several epidemiological studies. Animal and in vitro studies also indicate that DHA prevents amyloid deposition in the brain. Cross-sectional analysis of serum DHA levels together with measures of amyloid deposition (Pittsburgh Compound B index) on amyloid PET scan, brain volumes, and neuropsychological testing scores from 61 participants in the Aging Brain Study.
Serum DHA levels were 23% lower in participants with cerebral amyloidosis than those without (0.97 vs 1.25, P = .007) and were inversely correlated with brain amyloid load (r = −0.32, P = .01) independent of age, sex, apolipoprotein E genotype, and years of education. Moreover, greater serum DHA levels were positively associated with brain volume in several subregions affected by AD, in particular the left subiculum (r = 0.38, P = .005) and the left entorhinal volumes (r = 0.51, P = .001). Serum DHA levels were also associated with nonverbal memory scores (r =0.28, P = .03). DHA levels were inversely associated with pathogenesis of cerebral amyloidosis and with preservation of brain volumes. These findings suggest an important role for DHA metabolism in brain amyloid deposition during the preclinical or early symptomatic stages of Alzheimer disease.