The relationship between napping and memory varies as a function of genetic risk for Alzheimer's disease

BackgroundHabitual daytime napping is a significant aspect of many older adults' sleep-wake cycle. Growing evidence links napping and cognition in the context of Alzheimer's disease (AD), yet little is known about how genetic risk influences this relationship.ObjectiveThis study investigates interactions between genetic risk for AD and napping on cognition in 1655 cognitively healthy middle-aged to older adults.MethodsCognition was assessed using a self-administered online battery and reduced to three variables: memory, visuospatial abilities and executive functions. Genetic risk was assessed with the presence of <i>APOE</i> ɛ4 allele and polygenic risk scores for AD (PRS; excluding <i>APOE</i>). ANCOVA assessed interactions.ResultsThere was a significant interaction between <i>APOE</i> ɛ4 and napping duration on the memory component (<i>F</i>(2,1645) = 3.84, <i>p</i> = 0.022, ηp² = 0.005). <i>APOE</i> ɛ4 carriers reporting long naps demonstrated better memory than non-carriers also reporting long naps. Among <i>APOE</i> ɛ4 carriers, those who napped for ≥ 1 h performed better than those reporting shorter naps. In a separate analysis, there was a significant interaction between PRS and napping (<i>F</i>(2653) = 3.44, <i>p</i> = 0.033, ηp² = 0.010). Low PRS was related to better memory than high PRS among those who did not nap. Within the low PRS group, participants who did not nap outperformed those reporting short naps. Results remained significant after accounting for overnight sleep efficiency.ConclusionsFindings suggest that the relationship between napping and memory may vary as a function of genetic risk for AD. Results could inform studies looking into personalized preventative treatment based on genetic profiles.