A bad sleep score made people feel worse, and the score was fake

People with insomnia often report daytime symptoms, tiredness, fogginess, low mood, that do not line up neatly with what measurement says about their night. One explanation is that the belief about how you slept does some of the work, independently of the sleep itself. That question has become far more practical now that millions of people wake up to a sleep score generated by a wrist device, and those devices can disagree with laboratory measurement. This experiment set out to test whether feedback about sleep, on its own, changes how people appraise their day.

Sixty-three adults from the community who met DSM-5 criteria for insomnia disorder took part. After baseline assessments and a briefing on wearing an activity monitor, they were randomly assigned to receive either positive or negative feedback the next morning about their sleep efficiency. The feedback was sham, delivered at their usual rise time through a combined activity-monitor and diary watch designed to mimic how a consumer wearable behaves. Participants rated their symptoms immediately before receiving the feedback and again at 12:00 and 15:00 using experience sampling, then returned to the laboratory in the evening for further symptom reports and computerised tests of sleep-related attentional bias and basic psychomotor vigilance.

By evening, the 32 participants given negative feedback reported worse daytime function than the 31 given positive feedback, with less alert cognition and more sleepiness and fatigue. Tracking the day hour by hour, the positive-feedback group showed a greater rise in positive mood and alert cognition between rise time and midday, and a greater fall in sleepiness and fatigue, than the negative-feedback group. The objective measures told a different story: there were no significant differences between the groups on sleep-related attentional bias or on basic psychomotor vigilance. So the feedback moved how people judged their day without a matching change in measured reaction speed.

The result supports a long-suspected pathway in insomnia, in which misperception of sleep feeds the daytime symptoms that people find most disabling. It goes beyond correlation because the feedback was assigned at random, though it covers only a single morning and a single day of follow-up. The authors raise the obvious implication for wearables that market themselves as objective sleep measurement while sometimes disagreeing with gold-standard methods. What remains unknown is whether repeated inaccurate feedback over weeks or months compounds these effects, and whether people without insomnia respond the same way.

This is a reason to hold your sleep score loosely rather than treat it as a verdict on the day ahead. In this experiment, the number people were shown shaped how tired and how sharp they felt, even though the number was invented and their reaction times were unchanged. It does not mean tracking is useless, and it does not mean fatigue is imaginary; it means the feedback loop between belief and symptom is real enough to show up in a controlled test. If a poor score reliably ruins your morning, that reaction is itself part of the picture.