Circadian Environments

Science · Core 7

Sleep environment

The bedroom is a system.

Light, air, temperature and sound in the bedroom all act on sleep at once. Getting one right while another is wrong gives only part of the benefit.

Why it matters

Adults need at least seven hours of sleep a night on a regular basis for good health 1, and recommended ranges vary across life, from 7 to 9 hours for adults to 7 to 8 hours for older adults 2. In a national survey, between a third and nearly half of Australian adults reported inadequate sleep, in duration or quality, with daytime consequences 3.

Many things affect sleep that have nothing to do with the bedroom. But the bedroom is one of the few factors that can be measured and changed directly.

What the research shows

Light during sleep. In healthy adults, a single night of sleeping with moderate room light (100 lux) raised night-time heart rate and increased insulin resistance the next morning compared with sleeping in near darkness 4. In a study of older adults at home, those whose bedrooms averaged 3 lux or more at night had higher rates of obesity and abnormal blood lipids, although this type of study cannot show cause 5.

Air. Improving bedroom ventilation lowered CO2 and improved objectively measured sleep quality and next-day performance 6.

Temperature. Older adults slept most efficiently with bedroom temperatures between 20 and 25 °C 7.

Noise. Night-time noise fragments sleep and triggers stress responses 8.

Evening light before bed. Bright evening light delays melatonin and sleep timing. See Light 9.

What can be done

Make the room dark: blackout coverings and no glowing standby lights, with low, warm night lighting for safety. Make sure it gets fresh air overnight without draughts or noise. Keep it cool, with a way to control temperature on hot nights. Reduce noise at the window and door. Choose bedding and mattress materials with low emissions.

If sleep problems persist, see your GP. Conditions such as sleep apnoea and insomnia need medical assessment, and a better bedroom is not a substitute for that.

How we assess it

We log light, CO2, temperature, humidity and sound in the bedroom over several nights, and review window coverings, ventilation, heating and cooling, and bedding materials.

Evidence at a glance

  • Well supported

    Light at night, heat and noise each disturb sleep. 4,10,8

  • Reasonable

    Better bedroom ventilation improves sleep. Consistent but small studies. 6

General information only, not medical advice. How we grade evidence.

References

  1. Watson NF, Badr MS, Belenky G, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843-4. doi.org/10.5665/sleep.4716 · PubMed 26039963
  2. Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40-43. doi.org/10.1016/j.sleh.2014.12.010 · PubMed 29073412
  3. Adams RJ, Appleton SL, Taylor AW, et al. Sleep health of Australian adults in 2016: results of the 2016 Sleep Health Foundation national survey. Sleep Health. 2017;3(1):35-42. doi.org/10.1016/j.sleh.2016.11.005 · PubMed 28346149
  4. Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proc Natl Acad Sci U S A. 2022;119(12):e2113290119. doi.org/10.1073/pnas.2113290119 · PubMed 35286195
  5. Obayashi K, Saeki K, Iwamoto J, et al. Exposure to light at night, nocturnal urinary melatonin excretion, and obesity/dyslipidemia in the elderly: a cross-sectional analysis of the HEIJO-KYO study. J Clin Endocrinol Metab. 2013;98(1):337-44. doi.org/10.1210/jc.2012-2874 · PubMed 23118419
  6. Strøm-Tejsen P, Zukowska D, Wargocki P, Wyon DP. The effects of bedroom air quality on sleep and next-day performance. Indoor Air. 2016;26(5):679-86. doi.org/10.1111/ina.12254 · PubMed 26452168
  7. Baniassadi A, Manor B, Yu W, Travison T, Lipsitz L. Nighttime ambient temperature and sleep in community-dwelling older adults. Sci Total Environ. 2023;899:165623. doi.org/10.1016/j.scitotenv.2023.165623 · PubMed 37474050
  8. Halperin D. Environmental noise and sleep disturbances: a threat to health? Sleep Sci. 2014;7(4):209-12. doi.org/10.1016/j.slsci.2014.11.003 · PubMed 26483931
  9. Gooley JJ, Chamberlain K, Smith KA, et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J Clin Endocrinol Metab. 2011;96(3):E463-72. doi.org/10.1210/jc.2010-2098 · PubMed 21193540
  10. Okamoto-Mizuno K, Mizuno K. Effects of thermal environment on sleep and circadian rhythm. J Physiol Anthropol. 2012;31(1):14. doi.org/10.1186/1880-6805-31-14 · PubMed 22738673