REF-398 · Gavriloff D, Sheaves B, Juss A, Espie CA, Miller CB & Kyle SD, 2018 · Journal of Sleep Research, · Paper · PubMed
Sham sleep feedback delivered via actigraphy biases daytime symptom reports in people with insomnia: Implications for insomnia disorder and wearable devices
Participants
n=63 community participants meeting DSM-5 criteria for insomnia disorder
Protocol
After baseline assessment and an actigraphy briefing, participants were randomised to receive next-day sham feedback on their sleep quality: "positive" (n=31) or "negative" (n=32) sleep-efficiency condition
Feedback delivered at habitual rise-time through an integrated actigraphy-diary watch, to simulate wearable-device behaviour
Symptom reports immediately before feedback, then at 12:00 and 15:00 (experience sampling); in the evening, laboratory symptom reports plus computerised tests of sleep-related attentional bias and psychomotor vigilance
Key Results
Negative feedback impaired evening daytime function: decreased alert cognition (d = 0.79), increased sleepiness/fatigue (d = 0.55), compared with positive feedback
Within-day trajectories: the positive-feedback group showed a significantly greater increase in positive mood and alert cognition from rise-time to 12:00 and a significantly greater decrease in sleepiness/fatigue
No significant group differences on sleep-related attentional bias (d = 0.20) or psychomotor vigilance (d = 0.12)
Authors' conclusion: sham feedback about sleep biases the appraisal of daytime symptoms — a pathway from sleep misperception to the daytime features of insomnia — with implications for wearables that claim to measure "objective" sleep yet may be inaccurate against gold-standard measurement
Mechanism
Being told you slept poorly makes you feel and rate yourself worse the next day, independent of the feedback's truth — a nocebo route from information about a biological state to the subjective experience of that state. Note the boundary: the effect was on self-reported alertness, mood and sleepiness; objective psychomotor vigilance did not differ.
Practical Application
In 63 people with insomnia, a watch that falsely reported poor sleep produced lower self-rated alertness (d = 0.79) and more sleepiness/fatigue (d = 0.55) that evening than a watch that falsely reported good sleep — while a reaction-time test did not differ. A "bad sleep" number on a wearable changes how the day feels, even when the number is wrong.
Consider hiding daily sleep scores before key sessions or races; the feedback itself is an input to how tired the athlete will feel
Lead with the subjective morning check-in ("How do I feel?") rather than the device's sleep score
For coaches: never tell an athlete "your sleep was terrible" before a hard session — the feedback is part of the dose
Caveat: this is self-reported daytime function in insomnia patients; physical performance was not measured, and the objective vigilance test did not change
Limitations
Insomnia patients — may respond differently from healthy athletes
A single day of sham feedback
No exercise performance measured; outcomes are self-report plus a vigilance test that did not differ
How this entry was checked and changed
Content correction 2026-09-27
"Actual sleep quality did NOT predict daytime function — only the sham feedback did" -> the abstract does not report a test of actual sleep against daytime function; removed.
"Athletes feel more fatigued and perform worse based on the number" -> performance was not measured and psychomotor vigilance did not differ (d = 0.12); reworded, and the null results on attentional bias (d = 0.20) and vigilance added.
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