Why Shortened Monophasic Sleep is Bad


Choosing an effective schedule is an art that relies on certain science. It is a common misconception that one can simply invent a daily schedule of several short sleeps then feel rested and happy on it. In fact, such attempts usually lead to nothing more than weeks of debilitating sleep deprivation; eventually, termination of the sleep schedule and return to excessive monophasic sleep.

For two decades now, experimenters have been playing with theory and validating with trial and error. This will help save you months and even years of wasted efforts. During this time, people have had bad experiences with shortened monophasic sleep.

Why Shortened Monophasic Sleep Doesn’t Work

Numerous studies show that shortened monophasic sleep results in sleep deprivation with cognitive1, metabolic2, and cardiovascular3 consequences. There are various probable reasons for this:

  1. Light sleep only maintains wakefulness for a certain length of time. It usually takes about 5 sleep cycles, 50% of which is light sleep to stay awake and alert for the entire day. Meanwhile, some people need 4 or 6 cycles due to genetic variation, diet, stress, exercise, sleep quality, or environmental factors.
  2. Unlike in polyphasic sleep, sleep repartitioning does not happen much in one daily shortened sleep session.
  3. With shortened monophasic sleep, a 5 or 6-hour core cannot overlap both SWS and REM pressure peaks (21:00-midnight and 06:00-09:00 respectively). Hence, this inefficiency contributes to the insufficient repartitioning, resulting in REM and/or SWS sleep deprivation.
  4. The first sleep cycle in a sleep block typically has a higher percentage of SWS or REM than following cycles. The following cycles within a continuous block contain progressively more light sleep. This dynamic contrasts with polyphasic sleep, which has multiple “first cycles” that are each more REM or SWS efficient.
  5. With the repartitioning failure, sleep deprivation on shortened monophasic sleep causes REM or SWS rebounds in the following night sleep. Since this primarily affects the first 20m of a sleep in the form of SOREM or SOSWS, it is often insufficient to correct a previous day’s imbalance. Sleep deprivation therefore continues.
  6. A shortened monophasic schedule increases the waking duration compared to the length that regular monophasic sleep functions with.

Main authors: Crimson & Aethermind

Page last updated: 6 January 2021


  1. Durmer JS, Dinges DF. Neurocognitive consequences of sleep deprivation. Seminars in neurology. 2005;25(1):117-129. https://depressiongenetics.med.upenn.edu/uep/assets/user-content/documents/DurmerandDinges–NeurocognitiveConsequences–SEM.NEUROL.2005.pdf.
  2. Knutson K, Spiegel K, Penev P, Van C. The Metabolic Consequences of Sleep Deprivation. Sleep Med Rev. 2007;11(3):163-178. [PubMed]