Scott S. Campbell

Light Treatment for Sleep Disorders: Consensus Report VI. Shift Work

The unhealthy symptoms and many deleterious consequences of shift work can be explained by a mismatch between the work-sleep schedule and the internal circadian rhythms. This mismatch occurs because the 24-h zeitgebers, such as the natural light-dark cycle, keep the circadian rhythms from phase shifting to align with the night-work, day-sleep schedule. This is a review of studies in which the sleep schedule is shifted several hours, as in shift work, and bright light is used to try to phase shift circadian rhythms. Phase shifts can be produced in laboratory studies, when subjects are kept indoors, and faster phase shifting occurs with appropriately timed bright light than with ordinary indoor (dim) light. Bright light field studies, in which subjects live at home, show that the use of artificial nocturnal bright light combined with enforced daytime dark (sleep) periods can phase shift circadian rhythms despite exposure to the conflicting 24-h zeitgebers. So far, the only studies on the use of bright light for real shift workers have been conducted at National Aeronautics and Space Administration (NASA). In general, the bright light studies support the idea that the control of light and dark can be used to overcome many of the problems of shift work. However, despite ongoing practical applications (such as at NASA), much basic research is still needed.

Alleviation of sleep maintenance insomnia with timed exposure to bright light.

Objective: Half of the population over 65 suffers from chronic sleep disturbance. As a consequence, almost 40% of hypnotic medications are prescribed to people over age 60. Yet, hypnotics are often of little benefit in this population. As such, an effective non‐drug alternative could prove important in the management of age‐related sleep maintenance insomnia. The current study sought to evaluate the efficacy of bright light exposure in the treatment of sleep maintenance insomnia.

Light Treatment for Sleep Disorders: Consensus Report III. Alerting and Activating Effects

In addition to the well-established phase-shifting properties of timed exposure to bright light, some investigators have reported an acute alerting, or activating, effect of bright light exposure. To the extent that bright light interventions for sleep disturbance may cause subjective and/or central nervous system activation, such a property may adversely affect the efficacy of treatment. Data obtained from patient samples and from healthy subjects generally support the notion that exposure to bright light may be associated with enhanced subjective alertness, and there is limited evidence of objective changes (EEG, skin conductance levels) that are consistent with true physiological arousal. Such activation appears to be quite transient, and there is little evidence to suggest that bright light-induced activation interferes with subsequent sleep onset. Some depressed patients, however, have experienced insomnia and hypomanic activation following bright-light exposure.

Light Treatment for Sleep Disorders: Consensus Report V. Age-Related Disturbances

Sleep maintenance insomnia is a major complaint among the elderly. As a result, an inordinate proportion of sleeping pill prescriptions go to individuals over 65 y of age. Because of the substantial problems associated with use of hypnotics in older populations, efforts have been made to develop nondrug treatments for age-related sleep disturbance, including timed exposure to bright light. Such bright light treatments are based on the assumption that age-related sleep disturbance is the consequence of alterations in the usual temporal relationship between body temperature and sleep. Although studies are limited, results strongly suggest that evening bright light exposure is beneficial in alleviating sleep maintenance insomnia in healthy elderly subjects. Less consistent, but generally positive, findings have been reported with regard to bright light treatment of sleep and behavioral disturbance in demented patients. For both groups, it is likely that homeostatic factors also contribute to sleep disturbance, and these may be less influenced by bright light interventions.

Light Treatment for Sleep Disorders: Consensus Report VII. Jet Lag

Sleep disturbances are an all-too-familiar symptom of jet lag and a prime source of complaints for transmeridian travelers and flight crews alike. They are the result of a temporary loss of synchrony between an abruptly shifted sleep period, timed in accordance with the new local day-night cycle, and a gradually reentraining circadian system. Scheduled exposure to bright light can, in principle, alleviate the symptoms of jet lag by accelerating circadian reentrainment to new time zones. Laboratory simulations, in which sleep time is advanced by 6 to 8 h and the subjects exposed to bright light for 3 to 4 h during late subjective night on 2 to 4 successive days, have not all been successful. The few field studies conducted to date have had encouraging results, but their applicability to the population at large remains uncertain due to very limited sample sizes. Unresolved issues include optimal times for light exposure on the first as well as on subsequent treatment days, whether a given, fixed, light exposure time is likely to benefit a majority of travelers or whether light treatment should be scheduled instead according to some individual circadian phase marker, and if so, can such a phase marker be found that is both practical and reliable.

Light treatment for sleep disorders: consensus report. IV. Sleep phase and duration disturbances.

Advanced and delayed sleep phase disorders, and the hypersomnia that can accompany winter depression, have been treated successfully by appropriately timed artificial bright light exposure. Under entrainment to the 24-h day-night cycle, the sleep-wake pattern may assume various phase relationships to the circadian pacemaker, as indexed, for example, by abnormally long or short intervals between the onset of melatonin production or the core body temperature minimum and wake-up time. Advanced and delayed sleep phase syndromes and non-24-h sleep-wake syndrome have been variously ascribed to abnormal intrinsic circadian periodicity, deficiency of the entrainment mechanism, or—most simply—patterns of daily light exposure insufficient for adequate phase resetting. The timing of sleep is influenced by underlying circadian phase, but psychosocial constraints also play a major role. Exposure to light early or late in the subjective night has been used therapeutically to produce corrective phase delays or advances, respectively, in both the sleep pattern and circadian rhythms. Supplemental light exposure in fall and winter can reduce the hypersomnia of winter depression, although the therapeutic effect may be less dependent on timing.

Effects of a Nap on Nighttime Sleep and Waking Function in Older Subjects

Objectives: To examine, in older subjects, the effect on waking function of increasing 24‐hour sleep amounts by providing a nap opportunity; to assess what effects an afternoon nap may have on subsequent nighttime sleep quality and composition.

Physiology of the circadian system in animals and humans.

Virtually all organisms have developed an internal timing system capable of reacting to and anticipating environmental stimuli with a program of appropriately timed metabolic, physiologic, and behavioral events. The predominant biological rhythms coincide with the geophysical cycle of day and night-the circadian rhythms. The suprachiasmatic nuclei comprise the primary pace-maker in mammals, exhibiting the properties fundamental to a rhythm-generating structure. This article summarizes recent research that has elucidated mechanisms of signal transduction within the circadian system. The roles of various neurochemicals and hormones in transmitting the circadian timing signal are described. Properties of the circadian system, including photic and nonphotic entrainment, phase response curves, masking, and the intrinsic variability in the system are discussed.

Enhanced performance in elderly subjects following bright light treatment of sleep maintenance insomnia

Sixteen older individuals with sleep maintenance insomnia were treated with night‐time bright‐light exposure (BL) while living at home. Twelve consecutive days of acute light treatment were followed by a 3‐mo maintenance light‐treatment period. Subjects completed laboratory evaluation sessions on five separate occasions (prior to and following the acute light‐treatment period, and once per month during the maintenance period). During each laboratory session, performance levels, sleep, and core body temperature were measured. The performance battery consisted of four computerized tasks (Logical Reasoning, Stroop Congruency, Two Letter Visual Search, and Wilkinson Four‐Choice Reaction Time) and was administered every 2 h between 10.00 and 18.00 hours. Subjects improved significantly on three of the four tasks from pre‐BL to post‐BL. During the maintenance period, subjects who received active BL treatment maintained significantly higher performance levels than a control BL group. Light treatment improved sleep efficiency and delayed the phase of the body temperature rhythm. Performance improvements were significantly related only to sleep and not to circadian phase. The implications for non‐circadian treatments of sleep maintenance insomnia and cognitive functioning in the elderly are discussed.

Etiology and treatment of intrinsic circadian rhythm sleep disorders

Some individuals experience an acute or chronic sleep disturbance, associated with a misalignment between the timing of their sleep and the sleep-wake cycle that is desired, or considered normal by society. It is estimated that 5-10% of insomniacs seeking treatment have this type of disorder, collectively called circadian rhythm sleep disorders. This paper reviews circadian rhythm sleep disorders of the intrinsic type, which include delayed sleep phase syndrome, advanced sleep phase syndrome, non-24-hour sleep-wake syndrome, and irregular sleep-wake pattern. For each disorder, we present data addressing its pathophysiology and potential treatments, including the use of behavioral measures and chronotherapy, bright light treatment and pharmacological treatments such as melatonin. We conclude by addressing some of the limitations and drawbacks of the various treatments.