Apolipoprotein E4 and sex affect neurobehavioral performance in primary school children

Abstract

Apolipoprotein E4 (apoE4) and female sex are risk factors for developing Alzheimer's disease. It is unclear whether apoE4 contributes to behavioral function at younger ages. Standard neuropsychological assessments [intelligence quotient (IQ), attention, and executive function] and a test developed in this laboratory (Memory Island test of spatial learning and memory) were used to determine whether E4 and sex affect neuropsychological performance in healthy primary school children (age 7-10). A medical history was also obtained from the mother to determine whether negative birth outcomes were associated with apoE4. Mothers of apoE4+ children were more likely to report that their newborn was placed in an intensive care unit. A sex difference in birth weight was noted among apoE4- (males > females), but not apoE4+, offspring. Conversely, among apoE4+, but not apoE4- children, there was a sex difference in the Wechsler Abbreviated Scale of Intelligence (WASI) vocabulary score favoring boys. ApoE4- girls had better visual recall than apoE4+ girls or apoE4- boys on the Family Pictures test. Finally, apoE4+, unlike apoE4-, children did not show spatial memory retention during the Memory Island probe trial. Thus, apoE4 may affect neurobehavioral performance, particularly spatial memory, and antenatal health decades before any clinical expression of neurodegenerative processes.

Figure 1

Screen shot of Memory Island during a visible trial. If the target (insert) is not reached in two-minutes, an arrow appears (shown).

Figure 2

Performance of apoE4- and apoE4+ children on the Immediate (A) and Delayed (B) Family Pictures tests. *p<.05, **p<.01, or ^§p<.001versus apoE4- females.

Figure 3

Speed (virtual units/sec) on the visible and hidden trials of Memory Island. ▲:males; ∇females. (*p<.05 versus males).

Figure 4

Spatial memory retention of apoE4- and apoE4+ children in the probe trial of Memory Island. *p<.05 versus other quadrants, ■: target, □: left, : right, or : opposite quadrant (for additional details, see text).