Polarisbioseditoryour inner clock: a guide to body rhythms, light and sleep

An independent guide to biological rhythms, light and sleep. We do not diagnose or replace a doctor, and we are not affiliated with the previous website on this domain. If a life is in danger, call 112 (or your local emergency number).

Sources

Sources and limitations

Advice about sleep seems harmless, but your routine, your work and even your safety behind the wheel depend on it. That's why we rely on a small set of trustworthy sources, cite only verified figures, describe everything else in general terms and are honest about what this guide cannot do.

This guide explains how inner clocks work in general. Only a doctor can understand what is happening with yours.

— Editor's note

What we rely on

We check general information about circadian rhythms against the Nobel Committee's announcement: in 2017, the Nobel Prize in Physiology or Medicine was awarded for discoveries of molecular mechanisms controlling the circadian rhythm.

On sleep duration, we follow the recommendations issued in 2015 by the American Academy of Sleep Medicine and the Sleep Research Society: adults should regularly sleep 7 hours or more.

On physical activity, we follow the World Health Organization's 2020 guidelines on physical activity and sedentary behavior. Everything else we describe in general terms, without figures or references to individual studies.

Sources you can usually trust

  • International and national health organizations
  • Professional associations of sleep physicians and researchers
  • Your own doctor, who knows your health history
  • Texts that name the author, cite their sources and show an update date

How to check advice about sleep

  1. Who is the author?

    Does it say who wrote the text and whether they have relevant training? Someone else's personal experience may be interesting, but it is no basis for changing treatment.

  2. What are they asking you to buy?

    If sleep advice ends with a link to a device, an app or a supplement, read it especially critically.

  3. Does it match the recommendations?

    Compare the advice with the position of professional organizations and your doctor's opinion. A mismatch is a reason to ask questions, not to act right away.

  4. Does it promise instant results?

    The inner clock adjusts gradually. A promise to reset it in a single evening is a warning sign.

What this guide does not include

We do not make diagnoses, publish self-assessment questionnaires, name medicines or supplements, or discuss how to take them. We do not name specific clinics, specialists, devices or apps, and we are not connected to the previous website on this domain.

  • Research

    How to read news about sleep and body rhythms: bold headlines, mouse vs. human studies, surveys vs. experiments, and who paid for it.

  • Glossary

    Body rhythm terms in plain language: from circadian rhythm and chronotype to the sleep diary and polar day.

  • Approaches

    How to plan sleep and light around shift work, after a flight and above the Arctic Circle, who to see and how to keep a sleep diary.

  • Topics

    A map of topics: how the inner clock works, light through the day, chronotype, shift schedules, long flights, northern latitudes, plus the catalogue.

Sources

  • Nobel Committee — the 2017 Nobel Prize in Physiology or Medicine
  • American Academy of Sleep Medicine — recommendations on adult sleep duration (2015)
  • WHO — guidelines on physical activity and sedentary behavior (2020)

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.