Trials of supplementation with omega-3 fatty acids (ω3-FAs) in patients with mild cognitive impairment or Alzheimer's disease (AD) have produced inconsistent effects on cognitive decline. There is evidence of an interaction between B vitamin status and ω3-FAs in relation to brain atrophy and cognitive decline.
We investigated whether baseline levels of plasma total homocysteine (tHcy), a marker of B vitamin status, modify the effects of ω3-FAs supplementation on cognitive performance in moderate AD.
This post hoc analysis of the OmegAD trial included 171 community-based patients with AD (MMSE≥15): 88 patients received daily doses of 1.7 g docosahexaenoic acid and 0.6 g eicosapentaenoic acid for 6 months. Treatment outcome on cognition was analyzed according to baseline levels of tHcy using a general linear model and ANCOVA.
We found significant interactions between ω3-FA supplementation and tHcy on cognition and clinical stage assessed by MMSE (p = 0.040), global CDR (p = 0.059), and CDRsob (p = 0.023), but not on ADAS-cog (p = 0.649). In patients with tHcy levels <11.7μmol/L, ω3-FA supplementation improved cognitive performance as measured by MMSE (+7.1%, 95% CI: 0.59 to 13.7%, p = 0.033) and clinical status as measured by CDRsob (-22.3%, 95% CI: -5.8 to -38.7%, p = 0.009) compared with placebo.
The effect of ω3-FA supplementation on MMSE and CDR appears to be influenced by baseline tHcy, suggesting that adequate B vitamin status is required to obtain beneficial effects of ω3-FA on cognition.