Shift Work Sleep Disorder
(28/10/09)
What is shift work sleep disorder (SWSD)?
SWSD is classified as one of the circadian rhythm disorders (CRDs) and occurs in people who work shifts (particularly night shifts). It is caused by continued changes to a person's sleep-wake schedule. Most people demonstrate a remarkable ability to adjust to this repeated mismatching; however, individuals who experience persistent, severe symptoms are diagnosed as having SWSD. SWSD is characterised by disrupted or shortened duration of sleep and an inability to remain alert when required. Consequently, one of the main symptoms is Excessive Daytime Sleepiness (EDS), and this adversely affects the person's ability to perform the work required.
What are the symptoms of SWSD?
All patients with a CRD may complain of insomnia at certain times when they should be asleep and ES at other times. This disrupted sleep-wake pattern can impair the patient's functioning at work and in social situations. As a consequence, CRDs can cause the person distress. SWSD is no different: falling asleep at work or whilst driving can be extremely distressing, as well as potentially dangerous, and it may be this event that provokes the person to consult their doctor.
Sleep disruption in patients with SWSD is shown by shorter sleep duration and more frequent disturbances in sleep. In other words, patients will often have less sleep and what sleep they do get is less restorative or refreshing. In particular, when studied during their normal sleep hours, many patients with SWSD show a reduction in certain stages of sleep. The Multiple Sleep Latency Test (MSLT), a test used to evaluate a patient's sleepiness, shows a high degree of sleepiness during times when the patients are required to remain awake. This sleepiness is undoubtedly caused by the demands imposed by shift work. When studied following a period of adjustment to a normal sleep-wake schedule, these same individuals were shown to have normal night-time sleep and normal levels of daytime sleepiness and alertness.
No matter how long the patient has been working shifts, the 24 hour body timing system never completely adjusts to night work. Most night workers sleep during their nights off and workers who do this must adapt to a large shift in their sleep-wake schedule every week.
Dr. Bruno Baconnet
Senior Director
Medical Affairs
Cephalon Europe