"fast sleep" is a correct and usable phrase in written English.
It can be used to express the idea that something happened very quickly. For example, "I was so exhausted that I fell into a fast sleep as soon as my head hit the pillow."
We conclude that slow and fast sleep spindles travel different routes.
I can't tell you anything about that one because I fell fast sleep within minutes of it starting.
(The offending phrase was: "Drink fast, live fast, sleep late and rip it up down empty streets").
Mander, B. et al. Age-related impairments of memory and fast sleep spindles are mediated by deterioration of cortico-thalamic white matter pathways [abstract].
Schilling, C. et al. Fast sleep spindle reduction in schizophrenia and healthy first-degree relatives: association with impaired cognitive function and potential intermediate phenotype.
Giant panda cub Bao Bao was roused from slumber and carried before an adoring public Saturday, and within minutes was curled into a ball in the corner, fast sleep.
For days, he says, food tastes better, cars drive faster, sleep comes easier.
But emerging research shows that yoga may help you fall asleep faster, sleep longer, and sleep more soundly without the negative side effects of medication.
You may find that you'll be able to fall asleep faster, sleep more deeply, and wake up feeling more refreshed.
But some former members have painted a more troubling picture, accusing Tizer of controlling members through fasting, sleep deprivation and isolation from friends and family.
Napping happens "because children have a much faster sleep homeostasis — they build up sleep pressure more quickly, they are not so tolerant toward longer waking periods," said Dr. Oskar Jenni, a pediatrician who is director of the child development project at the University Children's Hospital Zurich.
