Pain Perception - Nociception during Sleep

During sleep, a state in which the brain is partially disconnected from external influences, subjects can be awakened by an episode of sudden pain. Approximately 2/3 of subjects who experience pain episodes report poor sleep quality, often accompanied by sequelae ranging from feeling unrefreshed to cognitive impairments such as memory and attention problems. Animal studies demonstrate that brief nociceptive stimulation tends to be processed similarly to sound, with dominant physiologic and behavioral responses during light sleep (stages 1 and 2) and attenuated responses during deep (stages 3 and 4) and rapid eye movement (REM) sleep. However, recent studies suggest that during sleep most somatosensory inputs are filtered below the thalamocortical pathway. At the behavioral level, if nociceptive stimulus is of a sufficient duration, a sleep arousal or sleep awakening response can be observed and, if perceived consciously, it can cause insomnia. Moreover, recent evidence suggests a circular influence between pain and sleep: a day of intense pain is followed by a night of poor sleep and a night with more sleep disruption is followed by an increase in pain the following day. The long-term health consequences of the exacerbation in pain and disruption in sleep homeostasis are unknown. It is critical that further investigation be made of the effects of pain medication (particularly opioids and other sedating agents) on sleep and daytime alertness, since sleep disturbance may interact with medication side-effects to magnify daytime sleepiness and cause a decrease in work productivity and safety and in driving performance, etc.