# Temperature and air

64–68 °F (18–20 °C). Don't crank the AC into a noisy on/off cycle.



## Takeaways

- 18–20 °C.

- Clean the AC filter.

- Fan not on your face.



Cool is right — generally 64–68 °F — but personal. Heat exposure measurably increases wakefulness and reduces deep and REM sleep; a falling core temperature is one of the triggers for sleep onset. Some prefer colder so they can use a heavier blanket.

When this idea went viral people cranked the AC; now we consistently see the AC kicking on and off waking people via sound change. Dirty AC units also throw dander and particulates into the air; a stuffy nose leads to mouth breathing and hypopnic/apneic events. A fan blowing at your face dries your mouth.

Temperature-regulating covers help if you're running hot; if you're not, you're already fine. Pillow/mattress/ergonomics: mostly feel; no hard rules.



## Sources

- Effects of thermal environment on sleep and circadian rhythm (Okamoto-Mizuno K, Mizuno K, 2012)

- The temperature dependence of sleep (Harding EC, Franks NP, Wisden W, 2019)

- Nighttime ambient temperature and sleep in community-dwelling older adults (Baniassadi A, Manor B, Yu W, Travison T, Lipsitz L, 2023)

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Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.

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