The effects of docosahexaenoic acid supplementation on cognition and well‐being in mild cognitive impairment: A 12‐month randomised controlled trial

This was a 12-month randomized controlled trial in independently living older adults aged 60 to 90 years with mild cognitive impairment and subjective memory concerns in New Zealand. For the DHA group, 37 participants were randomized and 30 were analyzed/completed.

Participants in the DHA arm took 3 capsules per day for 12 months, providing 1491 mg/day of triglyceride docosahexaenoic acid (DHA) and 351 mg/day of EPA. The capsules were matched to placebo in size, colour, and shape and also contained vitamin E and orange oil to mask taste.

DHA did not improve cognition or well-being overall compared with placebo, including no significant effects on cognitive measures at 12 months or at 6 months. A secondary physiological benefit was seen for systolic blood pressure, which increased more in the placebo group than in the DHA group, F(1,55) = 4.97, p = 0.03, η2 = 0.08. Among APOE ɛ4 carriers, treatment effects favored DHA for mood-related outcomes, with significant APOE ɛ4 by treatment interactions for GDS and GAI scores. The capsules were generally well tolerated, with only one gastrointestinal adverse effect reported in the DHA group.

The DHA arm was small, with attrition from 37 randomized to 30 analyzed, limiting power for cognitive outcomes. The significant mood findings were subgroup effects in APOE ɛ4 carriers and should be viewed as exploratory. The trial was conducted in a single country over 12 months, which may limit generalizability.