Research
Research overview
The science of biological rhythms is a serious field: in 2017, the Nobel Prize in Physiology or Medicine was awarded for discoveries of molecular mechanisms controlling the circadian rhythm. But news about sleep often keeps only a bold conclusion and drops the caveats. This section helps you understand what is really behind a headline.
A nocturnal mouse and a daytime human run on different clocks. Before changing your routine because of a news story, find out who it's actually about.
Mice, humans, surveys and experiments
| Type of study | How it's done | What it can tell you |
|---|---|---|
| Animal or cell study | Mechanisms are studied in the lab, for example in mice | How a process works in principle, but not how it will play out in a particular person |
| Survey | Participants report on their own sleep and habits | What people think about their routine; memories can be inaccurate |
| Observational study | Groups of people are followed and compared | Whether two things are linked, but not necessarily that one causes the other |
| Experiment in humans | Participants are randomly assigned to groups with different conditions | How a specific change works under set conditions |
| Review of many studies | Results from different studies are pooled together | The most balanced picture available at the moment |
What to ask a “scientists have proven” headline
Is there an original source?
Does it say who did the study and where it was published? Without that, the news is just a retelling of a retelling.
Who was it tested on?
Mice are mostly active at night and humans during the day, so conclusions about their rhythms can't simply be transferred from one to the other. Find out whether the study involved people.
How many participants were there?
A striking result in a small group may turn out to be a coincidence. The bigger and longer the study, the less room there is for chance.
Survey or experiment?
If people described their own sleep, that's valuable information but not proof of cause. A link between two things may be explained by a third.
Who funded it?
If the study was paid for by someone who sells sleep devices, drinks or supplements, that doesn't make it false, but its conclusions especially need independent checking.
What do professional organizations say?
If the news contradicts the recommendations of sleep experts and the WHO, it's wiser to wait for confirmation and discuss the question with a doctor.
Phrases worth double-checking
- “The secret to perfect sleep has been found” — sleep depends on many conditions at once
- “Night owls have worse lives than early birds” — studies describe groups, not the fate of an individual
- “This drink resets your inner clock” — there is often marketing behind it
- “Half as much sleep is enough” — this contradicts the recommendations on adult sleep
- “Works for everyone” — people differ in chronotype, age and health
Read next
- Sources
What sources this guide relies on, why it contains so few numbers and how to check advice about sleep and light yourself.
- Glossary
Body rhythm terms in plain language: from circadian rhythm and chronotype to the sleep diary and polar day.
- Topics
A map of topics: how the inner clock works, light through the day, chronotype, shift schedules, long flights, northern latitudes, plus the catalogue.
- Ask your doctor
Questions about sleep, shift schedules, daytime sleepiness and supplements that are worth raising with your own doctor.
Sources
- Nobel Committee — the 2017 Nobel Prize in Physiology or Medicine
- American Academy of Sleep Medicine — recommendations on adult sleep duration (2015)
This guide draws on the Nobel Committee's announcement of the 2017 prize, the recommendations on adult sleep duration and the WHO guidelines on physical activity as they were available when the texts were written. Scientific understanding of sleep rhythms keeps evolving, so questions about your own health are best discussed with a doctor.