Alzheimer's gene affects IQ from childhood
Analysis of some old longitudinal studies has found that those carrying the APOE4 gene scored lower on IQ tests during childhood and adolescence. The effect was much stronger in girls than in boys, and affected reasoning most strongly.
IQ scores were lower by 1.91 points for each APOE4 allele carried. But boys scored only an average of 0.33 points lower, while girls scored almost 3 points lower for each APOE4 allele.
Almost all the participants (92%) were white.
Impaired learning linked to family history of Alzheimer's
A large internet-based study found that adults with a first-degree relative with Alzheimer's disease performed worse on a paired-learning task than adult without such a family history, and this impairment appears to be exacerbated by having diabetes or the APOE4 gene.
The online word-pair memory test (called MindCrowd) involved learning 12-word pairs and then completing the missing half of the pair when presented with one of the words. 59,571 individuals participated. Those with a family history of Alzheimer's were able to match about two and one-half fewer word pairs than individuals without a family history.
The family history effect was particularly pronounced among men, as well as those with lower educational attainment, diabetes, and carriers of APOE4.
The effect of family history was shown across every age group, up until age 65.
A subset of 742 participants who had a close relative with Alzheimer's were tested for the APOE gene.
Reynolds, C.A. et al. 2019. APOE effects on cogntion from childhood to adolescence. Neurobiology of Aging, Available online 18 April 2019.
(2019). Family history of Alzheimer’s disease alters cognition and is modified by medical and genetic factors.
(Irish, M., & Franco E., Ed.).eLife. 8, e46179.