Consideration of sleep dysfunction in rehabilitation.

The physiology of sleep is not completely understood but it is widely accepted that sleep is important to the human body in the recovery of metabolic and neurological processes. This paper summarizes the effects of sleep dysfunction on different systems and considers implications in the context of rehabilitation. When sleep is experimentally completely or partially curtailed important brain functions are impacted leading to psychological and neurological disturbances. Increased cortisol levels, reduction of glucose tolerance, and increased sympathetic nervous system activity have also been identified in healthy subjects under such conditions. Several studies show that 50-80% of patients with chronic pain suffer from sleep dysfunction. It has been suggested that on the one hand pain can cause sleep dysfunction and on the other hand that sleep dysfunction can aggravate pain. The physiologic mechanism behind this interaction is not completely clear; although most authors describe the relationship between pain and sleep dysfunction as aberrant processing of tactile-cutaneous sensory inputs at the meso-encephalic level and in the trigeminal nucleus both when asleep and awake. Decreased duration of sleep also increases heart rate, blood pressure and sympathetic activity magnifying the individual's response to stressful stimuli. Possible causal mechanisms for the established connection between short sleep cycles and coronary pathology include sympathetic nervous system hyperactivity, increased blood pressure increase or reduced glucose tolerance. Finally, sleep and fatigue have traditionally been linked. Fatigue can have a physical etiology but is also associated with depression. Sleep alterations are also considered an important risk factor for psychological dysfunction and also mental illness. However, despite the noted repercussions of sleep dysfunction, studies investigating interventions to improve sleep have been limited in number. Benefits of exercise programs on sleep habits have been controversial with some have finding positive effects, whereas others did not find any significant effect. It is possible that the dose or intensity of exercise programs may have an important influence in the outcomes. It is our opinion that based on the multi-system repercussions of different sleep dysfunctions, evaluation of sleep habits should be considered fundamental in the context of rehabilitation and should be included as part of the clinical history of each patient attending physical therapy.