Apolipoprotein E and Its Association With Cognitive Change and Modification of Treatment Effects of Vitamin D3 and Omega-3s on Cognitive Change: Results From the In-Clinic Subset of a Randomized Clinical Trial

Background: Apolipoprotein E (APOE)-ε4 allele is associated with cognitive decline; however, its potential to modify effects of vitamin D3 and omega-3s supplementation on later-life cognition is unclear. Our objectives were to estimate among the in-clinic subset of a randomized trial: (1) associations between APOE-ε4 and global and domain-specific cognitive change, with exploration of potential sex and race differences; and (2) modification by APOE-ε4 of effects of vitamin D3 and omega-3s supplementation on cognitive change.

Methods: From an ancillary study of depression prevention within a completed 2 × 2 factorial trial testing vitamin D3 (2 000 IU per day), omega-3s (1 g per day), and/or placebos, we included 743 older adults with baseline in-person neuropsychiatric assessments and APOE genotyping data. The primary outcome was change in global cognition (averaging z-scores of 9 tests) over 2 years. Secondarily, episodic memory and executive function/attention z-scores were examined. General linear models of response profiles with multiplicative interaction terms were constructed; stratified results were reported.

Results: Mean age (standard deviation) was 67.1 (5.3) years; 50.6% were females; 24.9% were APOE-ε4 carriers. Compared to noncarriers, APOE-ε4 carriers had worse 2-year change in global cognition and episodic memory; differences were more apparent among females than males. There was no variation by race in APOE-ε4 associations with cognition. APOE-ε4 did not significantly modify effects of vitamin D3 or omega-3s, compared to placebo, on change in global cognition, episodic memory, or executive function/attention.

Conclusions: APOE-ε4 was associated with worse cognition but did not modify overall effects of vitamin D3 or omega-3 supplementation on cognition over 2 years.