PULMONARY AND SLEEP DISORDERS
Shift Work Sleep Disorder By Daniel T. Layish, MD, FACP, FCCP, FAASM
Optimal sleep and wakefulness requires proper alignment between an individual’s intrinsic circadian rhythm and their desired sleep wake schedule. The word circadian comes from the Latin “circa” meaning “about” and “dian” meaning “day”. Our intrinsic circadian rhythm is controlled by an internal clock in the hypothalamus (suprachiasmatic nucleus). The hypothalamus receives signals from the retina that entrain the circadian rhythm to the light dark cycle. The circadian rhythm affects the timing of sleep. There is also a homeostatic sleep drive, which controls sleep intensity, and it is determined by how long an individual has been awake. Shift work sleep disorder is a recurrent or persistent mismatch between a person’s habitual sleep wake schedule and their endogenous circadian rhythm. Shift work sleep disorder can be associated with insomnia or excessive sleepiness (or both). The conventional time cues (zeitgeber = “time giver” in German) of sunlight and social activities are frequently out of phase with the altered sleep schedule in an individual with shift work sleep disorder. Many shift workers revert back to their traditional daytime schedule during non-work days. By definition, the course of shift work sleep disorder parallels the period of the shift work and remits with termination of shift work. An individual SLEEP FACTORS with shift work sleep disorder may use a large portion of their free time for recovery of sleep, which may have negative social consequences such as marital discord and impaired social relationships. Shift work sleep disorder tends to be more common after age 50. Between 5 and 8% of the population is exposed to night work on a regular or periodic basis. Shift work sleep disorder is usually a clinical diagnosis. A formal sleep study (polysomnogram) may be helpful to exclude other etiologies of a patient’s symptoms. The sleep study should ideally be performed during the regular hours of sleep of the individual having the study. To diagnose shift work sleep disorder one must exclude any other medical or psychiatric conditions which could account for the symptoms. In addition, the symptoms should not meet criteria for any other sleep disorder which can produce insomnia or excessive daytime sleepiness (such as Jet-lag syndrome). Women appear to be slightly more prone to developing shift work sleep disorder. Interestingly, women tend to quit their shift work less often than men. The occurrence of shift work sleep disorder may vary depending upon the speed and direction 8 FLORIDA MD - AUGUST 2021
of shift rotation. It may also vary depending upon a patient’s diurnal preference. It appears to be less common in individuals who identify themselves as “night owls”. Individuals with shift work sleep disorder have been found to have higher rates of peptic ulcer disease as well as more sleepiness related motor vehicle accidents. Other consequences of this disorder include absenteeism from work, higher rates of depression and missed family and social activities as well as chronic fatigue and poor work performance. There have also been studies which link shift work sleep disorder to glucose intolerance as well as higher risk for alcohol and substance use. Sleep CIRCADIAN FACTORS
SHIFT WORK COPING ABILITY
ENVIRONMENTAL FACTORS
diaries can be helpful in assessing patients with shift work sleep disorder. Actigraphy can be useful as an adjunct to history, physical exam and sleep diary. Actigraphy recording should consist of at least three consecutive 24-hour periods. Circadian rhythm markers (such as core body temperature monitoring or timing of melatonin secretion) are more difficult and typically are not used in routine clinical settings. Treatment for shift work sleep disorder can include exposure to bright light in the work place as well as administration of wake promoting agents during evening work hours. Other treatments include scheduled napping as well as hypnotic agents to improve daytime sleep. Maintaining a regular sleep wake schedule during both work and non-work days is also recommended (as well as minimizing light or noise in the bedroom and allowing sufficient time in bed for sleep during the daytime). Other recommendations include limiting light exposure by using dark sunglasses during the morning trip home from work. The timing of
