Journal of sleep researchApr 6, 2017

How grogginess after sleep affects focusing on rare visual targets and varies with sleep timing preference

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 25, 2026

Abstract

Cognitive throughput and reaction times of correct responses were impaired by sleep inertia and took ~10-30 minutes to improve after awakening.

Sleep inertia is influenced by circadian phase, with worse performance occurring during the biological night compared to the biological day.
Later chronotypes experienced longer durations of sleep inertia, taking ~30 minutes or longer to show significant improvement in performance after awakening.
In contrast, earlier chronotypes demonstrated significant performance improvement within ~10-20 minutes post-awakening.
The study analyzed performance data from 18 healthy participants, revealing individual differences in response to sleep inertia based on chronotype.
Findings align with circadian theory, indicating that later chronotypes may face prolonged cognitive impairments immediately after waking.

Simplified

Sleep inertia is affected by circadian phase, with worse performance upon awakening from sleep during the biological night than biological day. Visual search/selective visual attention performance is known to be sensitive to sleep inertia and circadian phase. Individual differences exist in the circadian timing of habitual wake time, which may contribute to individual differences in sleep inertia. Because later chronotypes awaken at an earlier circadian phase, we hypothesized that later chronotypes would have worse visual search performance during sleep inertia than earlier chronotypes if awakened at habitual wake time. We analysed performance from 18 healthy participants [five females (22.1 ± 3.7 years; mean ± SD)] at ~1, 10, 20, 30, 40 and 60 min following electroencephalogram-verified awakening from an 8 h in-laboratory sleep opportunity. Cognitive throughput and reaction times of correct responses were impaired by sleep inertia and took ~10-30 min to improve after awakening. Regardless whether chronotype was defined by dim light melatonin onset or mid-sleep clock hour on free days, derived from the Munich ChronoType Questionnaire, the duration of sleep inertia for cognitive throughput and reaction times was longer for later chronotypes (n = 7) compared with earlier chronotypes (n = 7). Specifically, performance for earlier chronotypes showed significant improvement within ~10-20 min after awakening, whereas performance for later chronotypes took ~30 min or longer to show significant improvement (P < 0.05). Findings have implications for decision making immediately upon awakening from sleep, and are consistent with circadian theory suggesting that sleep inertia contributes to longer-lasting impairments in morning performance in later chronotypes.

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Competing interests

Conflicts of Interest: H.K.R., T.M.B., T.B.D., A.W.M. and J.A. report no conflicts; K.P.W.: Funding: NIH, Office of Naval Research, Philips Inc., Torvec Inc.; Consulting fees or served as a paid member of scientific advisory boards for NIH, Torvec Inc.; Speaker honorarium from American College of Chest Physicians, The Obesity Society, Obesity Medicine Association.

PubMed

How grogginess after sleep affects focusing on rare visual targets and varies with sleep timing preference

Abstract

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