Does possession of apolipoprotein E ɛ4 benefit cognitive function in healthy young adults?

There is considerable evidence that the apolipoprotein E (APOE) ɛ4 allele is associated with cognitive deficits in older persons, and is a risk factor for dementia. However, it has recently been suggested that possession of the ɛ4 allele may benefit cognition in early adulthood. We tested this possibility in 5445 community-dwelling persons aged 20-24, 40-44, and 60-64 years using a comprehensive battery of cognitive measures. As the APOE ɛ2 allele may offer protection against cognitive deficits, in order to robustly test the hypothesis, we removed persons carrying this allele from the analyses. Older persons with possible dementia were also removed. We found no evidence of higher cognitive performance in young ɛ4 carriers, or cognitive deficits in older ɛ4 carriers. This did not change when a range of health variables were taken into account. We conclude that it is premature to suppose ɛ4-related benefits to cognition in healthy young adulthood and findings consistent with this hypothesis may have been related to methodological issues, or the pathology of the sample investigated.