Sleep science, in plain English
What new sleep and body-clock studies actually found. Each briefing covers what the researchers did, what they found, the limits of the study, and links to the original paper.
Latest briefings
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Light & the body clock
Reading on a tablet before bed pushed people's body clocks back by over 90 minutes
A tightly controlled lab study compared four hours of evening reading on an iPad with the same reading from a printed book. The screen changed melatonin, sleep timing and next-morning alertness.
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Insomnia
Waking in the night, not trouble dropping off, was linked with daytime sleepiness
Researchers looked at how three common insomnia symptoms related to feeling sleepy in the day. People who woke repeatedly in the night tended to be sleepier, while people who struggled to fall asleep tended to be less sleepy.
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Mind & sleep
How people rate their sleep, not their brain waves, was linked with underestimating it
Researchers compared how long 225 adults thought they had slept with how long a sleep-lab recording said they slept. How people rated their sleep quality was more closely linked with underestimating their sleep than anything in their brain-wave recordings.
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Sleep & health
In type 2 diabetes, 7 to 8 hours of sleep was linked with the fewest complications
Researchers followed 1,236 adults with type 2 diabetes to see who went on to develop damage to the kidneys, eyes or nerves. People who slept under 7 hours, or 10 hours or more, had a higher risk than those who slept 7 to 8 hours.
How we rate evidence
- Early evidence
- Small, short or lab-based studies, animal work and preprints. Interesting, but it may not hold up.
- Moderate evidence
- Larger trials or well-run observational studies in people. Worth knowing, but not the final word.
- Strong evidence
- Systematic reviews and meta-analyses, or several large trials that agree.