The possibility that ε4 may modulate the effects of fitness in the brain remains controversial. The present exploratory FDG-PET study aimed to better understand the relationship among ε4, fitness and cerebral metabolism in 18 healthy aged females (9 Carriers, 9 Non-carriers) during working memory.

Participants underwent VO₂ max, CVLT and FDG-PET, collected at rest and during completion of the Sternberg Working Memory Task.

Resting FDG-PET did not differ between carriers and non-carriers. Significant effects of fitness on FDG-PET during working memory was noted in the ε4 carriers only. High Fit ε4 carriers had greater glucose uptake than the Low Fit in the temporal lobe, but Low Fit had greater glucose uptake in the frontal and parietal lobes.

We demonstrate that fitness differentially affects cerebral metabolism in ε4 carriers only, consistent with previous findings that the effects of fitness may be more pronounced in populations genetically at risk for cognitive decline.