Baseer Maroof, LCSW · Raleigh, NC · Adults 21+
Sleep pressure & the body clock
Why the nap that felt so good on Tuesday is the reason you were wide awake at midnight.
In short
- Two systems time your sleep: Process S, sleep pressure that builds the longer you’re awake, and Process C, your body clock.
- Sleep comes easiest when pressure is high and the clock stops pushing you to stay alert.
- Naps, sleeping in and going to bed early all lower pressure at bedtime.
- A fixed rise time is the single best anchor for both.
Play with it
Sleep pressure vs body clock
Move wake time and bedtime, or add a nap. Watch the white line at lights out.
An illustration of Borbély’s two-process model, not a measurement of you. The shapes are simplified to show the idea.
Process S: sleep pressure
How it works
Pressure to sleep builds through the day and drains off during sleep. A nap spends some of it early. This is the lever sleep restriction pulls. (Borbély 1982; Borbély et al. 2016)
Process C: the body clock
How it works
Your circadian clock runs roughly on a 24-hour cycle and sets when you feel alert and when sleep comes easily, separate from how long you’ve been awake. Morning light and a consistent wake time keep it set. (Borbély et al. 2016)
What this means for you
Do
- Same rise time every day.
- Get daylight and move during the day.
- Go to bed when sleepy, not just because it’s “time.”
Go easy on
- Long or late naps.
- Sleeping in after a bad night.
- Early nights to “catch up.”
Each one feels like repair and leaves you with less drive the next night.
Sources
All sources, linked3 references⌄
- Borbély AA (1982). A two process model of sleep regulation. Hum Neurobiol 1(3):195–204. pubmed.ncbi.nlm.nih.gov/7185792/
- Borbély AA, Daan S, Wirz-Justice A, Deboer T (2016). The two-process model of sleep regulation: a reappraisal. J Sleep Res 25(2):131–143. pubmed.ncbi.nlm.nih.gov/26762182/
- Spielman AJ, Yang C-M, Glovinsky PB (2011). Sleep restriction therapy. In Perlis M, et al. (eds), Behavioral Treatments for Sleep Disorders. Elsevier (chapter hosted by the Penn CBT-I program). www.med.upenn.edu/cbti/assets/user-content/documents/BTSD%20Spielman%20Chapter%20on%20SRT.pdf
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