APOE genotype and plasticity in cognitive training

Rationale: The major known genetic risk factor for sporadic Alzheimer´s disease (AD) is the Ɛ4 variant of the apolipoprotein E (APOE) allele. APOE has been suggested to affect plasticity. The literature is scarce, but... [ view full abstract ]

Rationale: The major known genetic risk factor for sporadic Alzheimer´s disease (AD) is the Ɛ4 variant of the apolipoprotein E (APOE) allele. APOE has been suggested to affect plasticity. The literature is scarce, but evidence from clinical populations suggest that Ɛ4-carriers may show less cognitive plasticity in response to intervention. As episodic memory decline is a hallmark of AD, it is of interest to study whether APOE allelic variation impacts memory plasticity in a controlled experimental intervention. Methods and analyses: In a study of effects of strategic episodic memory training in healthy adults in their 20s and 70s, we investigated the effects of the naturally occurring variation in APOE allelic variants on training gains (absence vs presence of Ɛ4-allele; N = 132, 47 young and 85 older, of whom 23.4% and 23.5% Ɛ4-carrieres, respectively; 2.3% of the total sample had two Ɛ4 alleles). Memory gains were calculated through change in serial recall of word lists consisting of 100 words. Results: Participants showed significant increase in memory after training compared to passive and active control conditions. On average, Ɛ4-carriers and non-carriers recalled 14.1 (SD 7.6) and 13.1 (SD 6.6) words pre-memory training, and 25.7 (SD 12.7) and 26.5 (SD 13.6) post-memory training. There were effects of intervention (pre, post) and age group, and an interaction of intervention and age group, with greater plasticity in younger (p <.001), but no effect or trend towards effect of APOE (F = .067, p = .796), nor any interactions of APOE*intervention or APOE* intervention*age group. Conclusions: The present study indicated no significant effects of absence vs presence of an APOE Ɛ4-allele on memory plasticity in healthy adults. There were few with two APOE Ɛ4 alleles, effects of which should be subject to future investigations. Power analysis suggested that a sample of > 1600 individuals would be required to detect the presently observed small difference in plasticity. Training gains were ample in both groups. Hence, the present results indicate that healthy carriers of an APOE Ɛ4 allele benefit from memory training in a largely comparable manner to non-carriers.