Effects of sleep inertia after daytime naps vary with executive load and time of day.

Thirty-two healthy adults (mean 22.5 ± 3.0 years) participated in assessments of working memory performance after morning or afternoon naps.

• Afternoon naps were associated with shorter sleep latencies, longer sleep duration, and more Slow Wave Sleep compared to morning naps.
• Working memory performance declined and subjective mental workload increased at higher levels of executive load.
• Participants showed poorer performance on more complex working memory tasks (e.g., 3-back) following afternoon naps.
• No significant performance differences were observed between waking and napping groups on simpler tasks.
• After approximately 30 minutes of cognitive activity, performance differences between groups diminished.
• Subjective mental effort and task difficulty were less influenced by sleep inertia following afternoon naps.

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