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Abstracts

• Sleep, shift-work and jet-lag syndrome

AUTHOR(S): Eastman CI; Boulos Z; Terman M; Campbell SS; Dijk DJ; Lewy AJ

AUTHOR'S ADDRESS: Biological Rhythms Research Laboratory, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612, USA.

ARTICLE TITLE: Light treatment for sleep disorders: consensus report. VI. Shift work.

ARTICLE SOURCE: J Biol Rhythms (United States), Jun 1995, 10(2) p157-64

ABSTRACT: 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.

AUTHOR(S): Hirschfeld U; Moreno-Reyes R; Akseki E; L'Hermite-Baleriaux M; Leproult R; Copinschi G; Van Cauter E

AUTHOR'S ADDRESS: Department of Medicine, University of Chicago, Illinois 60637, USA.

ARTICLE TITLE: Progressive elevation of plasma thyrotropin during adaptation to simulated jet lag: effects of treatment with bright light or zolpidem.

ARTICLE SOURCE: J Clin Endocrinol Metab (United States), Sep 1996, 81(9) p3270-7

ABSTRACT: It is well known that TSH secretion is modulated by sleep and circadian rhythmicity, but effects of abrupt shifts of the sleep-wake and dark-light cycles such as occur in jet lag and shift work have not been investigated. The present study examines alterations in the 24-h profiles of plasma TSH and thyroid hormones following an 8-h advance shift achieved without enforcing prolonged sleep deprivation. The effects of bright light exposure or sleep facilitation with zolpidem were investigated in separate studies performed in the same subjects. Each study involved blood sampling at 20-min intervals for 68 h and included a baseline period with dim light during waking hours and 2300-0700 h bedtimes in total darkness. The 8-h shift was achieved by advancing bedtimes to 1500-2300 h. In the course of adaptation to the shift, TSH levels increased progressively in all three studies because daytime sleep failed to inhibit TSH and nighttime wakefulness was associated with large TSH elevations. The overall elevation of TSH tended to be paralleled by a small increase in T3, but not free T4, levels. In the absence of treatment, mean TSH levels following awakening from the second shifted sleep were more than 2-fold higher than during the same time interval following normal nocturnal sleep (2.10 +/- 0.22 mU/L vs. 1.04 +/- 0.14 mU/L; n = 8, P 0.001). Bright light exposure limited the overall increase of TSH, and mean TSH levels at the end of the study were lower than in the absence of treatment (P 0.03). Treatment with zolpidem during the first shifted night limited the overall increase in TSH levels during the following waking period (P 0.05), but the beneficial effect was no longer significant following the second shifted night. Thus, the jet lag syndrome may be associated with a prolonged elevation of peripheral TSH levels that may be limited by treatment with bright light exposure or hypnotic facilitation of sleep.

AUTHOR(S): Iwata N; Ichii S; Egashira K

AUTHOR'S ADDRESS: Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan.

ARTICLE TITLE: Effects of bright artificial light on subjective mood of shift work nurses.

ARTICLE SOURCE: Ind Health (Japan), 1997, 35(1) p41-7

ABSTRACT: The effects of bright artificial light on the subjective mental state of 10 female nurses working shifts at a university hospital were assessed. We investigated two series of five consecutive workshifts rotations comprising one normal, two night and two evening shifts, using two self-administered rating scales. The subjects were exposed to artificial light, brighter than 3,000 lux, for a total of 30 min during each workshift of the second series, whereas they worked under normal lighting conditions (approximately 250 lux) during the first series. A three-way layout ANOVA, with repeated measures, revealed that bright light tended to improve eagerness and reduce tension, and improved vigor, eagerness, appetite and impairment (the latter only on the second night) significantly or nearly significantly during night, but not evening, shifts. These results suggest that bright artificial light affects the mental state of nurses during night, but not evening, shift work.

AUTHOR(S): Mishima K; Okawa M; Hishikawa Y; Hozumi S; Hori H; Takahashi K

AUTHOR'S ADDRESS: Department of Neuropsychiatry, Akita University School of Medicine, Japan.

ARTICLE TITLE: Morning bright light therapy for sleep and behavior disorders in elderly patients with dementia.

ARTICLE SOURCE: Acta Psychiatr Scand (Denmark), Jan 1994, 89(1) p1-7

ABSTRACT: Fourteen inpatients with dementia showing sleep and behavior disorders (average age = 75 years), and 10 control elderly people (average age = 75 years) were carefully observed for 2 months. Four weeks of morning light therapy markedly improved sleep and behavior disorders in the dementia group. The measurement of sleep time and the serum melatonin values suggests that sleep and behavior disorders in the dementia group are related to decreases in the amplitude of the sleep-wake rhythm and decreases in the levels of melatonin secretions. Morning light therapy significantly increased total and nocturnal sleep time and significantly decreased daytime sleep time. These results indicate that morning bright light is a powerful synchronizer that can normalize disturbed sleep and substantially reduce the frequency of behavior disorders in elderly people with dementia.

AUTHOR(S): Neumeister A; Goessler R; Lucht M; Kapitany T; Bamas C; Kasper S

AUTHOR'S ADDRESS: Department of General Psychiatry, University of Vienna, Austria.

ARTICLE TITLE: Bright light therapy stabilizes the antidepressant effect of partial sleep deprivation.

ARTICLE SOURCE: Biol Psychiatry (United States), Jan 1 1996, 39(1) p16-21

ABSTRACT: Partial sleep deprivation (PSD) results in a pronounced decrease of depressive symptoms in the majority of patients with major depressive disorder. Generally this acute antidepressant effect is not stable, relapse usually occurs after one night of recovery sleep. We therefore studied whether light therapy, beginning in the morning after PSD, is able to prevent the relapse after sleep deprivation, using a controlled, balanced, parallel design. All patients received an antidepressant medication, which was kept constant before and during the study period. Fourteen of 20 patients (70%) showed a reduction of at least 40% in the Hamilton Depression Rating Scale (HDRS) in the morning after PSD and were classified as PSD responders. Responders as well as nonresponders were randomly assigned to receive either bright light (BL/3000 lux) or dim light (DL/100 lux) therapy during the following 6 days after PSD. In the responder group BL therapy prevented significantly (p = 0.005) the relapse after the next night of sleep and prolonged significantly (p = 0.011) the antidepressant effects of PSD up to 7 days. In contrast, patients in the DL condition relapsed after the recovery night and showed no further improvement of the depressive syndrome after 1 week of DL therapy. PSD nonresponders did not benefit from light treatment. These findings indicate that BL therapy might be efficacious to prevent relapse after PSD.

AUTHOR(S): Terman M; Lewy AJ; Dijk DJ; Boulos Z; Eastman CI; Campbell SS

AUTHOR'S ADDRESS: Department of Psychiatry, Columbia University and New York State Psychiatric Institute, NY 10032, USA.

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

ARTICLE SOURCE: J Biol Rhythms (United States), Jun 1995, 10(2) p135-47

ABSTRACT: 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.

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