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Atkinson, G., & Davenne, D. (2007). Relationships between sleep, physical activity and human health. Physiol Behav, 90(2-3), 229–235.
Abstract: Although sleep and exercise may seem to be mediated by completely different physiological mechanisms, there is growing evidence for clinically important relationships between these two behaviors. It is known that passive body heating facilitates the nocturnal sleep of healthy elderly people with insomnia. This finding supports the hypothesis that changes in body temperature trigger somnogenic brain areas to initiate sleep. Nevertheless, little is known about how the core and distal thermoregulatory responses to exercise fit into this hypothesis. Such knowledge could also help in reducing sleep problems associated with nocturnal shiftwork. It is difficult to incorporate physical activity into a shiftworker's lifestyle, since it is already disrupted in terms of family commitments and eating habits. A multi-research strategy is needed to identify what the optimal amounts and timing of physical activity are for reducing shiftwork-related sleep problems. The relationships between sleep, exercise and diet are also important, given the recently reported associations between short sleep length and obesity. The cardiovascular safety of exercise timing should also be considered, since recent data suggest that the reactivity of blood pressure to a change in general physical activity is highest during the morning. This time is associated with an increased risk in general of a sudden cardiac event, but more research work is needed to separate the influences of light, posture and exercise per se on the haemodynamic responses to sleep and physical activity following sleep taken at night and during the day as a nap.
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Boivin, D. B., Boudreau, P., James, F. O., & Kin, N. M. K. N. Y. (2012). Photic resetting in night-shift work: impact on nurses' sleep. Chronobiol Int, 29(5), 619–628.
Abstract: The objective of this study was to quantify daytime sleep in night-shift workers with and without an intervention designed to recover the normal relationship between the endogenous circadian pacemaker and the sleep/wake cycle. Workers of the treatment group received intermittent exposure to full-spectrum bright light during night shifts and wore dark goggles during the morning commute home. All workers maintained stable 8-h daytime sleep/darkness schedules. The authors found that workers of the treatment group had daytime sleep episodes that lasted 7.1 +/- .1 h (mean +/- SEM) versus 6.6 +/- .2 h for workers in the control group (p = .04). The increase in total sleep time co-occurred with a larger proportion of the melatonin secretory episode during daytime sleep in workers of the treatment group. The results of this study showed reestablishment of a phase angle that is comparable to that observed on a day-oriented schedule favors longer daytime sleep episodes in night-shift workers. (Author correspondence: diane.boivin@douglas.mcgill.ca ).
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Cajochen, C., Altanay-Ekici, S., Munch, M., Frey, S., Knoblauch, V., & Wirz-Justice, A. (2013). Evidence that the lunar cycle influences human sleep. Curr Biol, 23(15), 1485–1488.
Abstract: Endogenous rhythms of circalunar periodicity ( approximately 29.5 days) and their underlying molecular and genetic basis have been demonstrated in a number of marine species [1, 2]. In contrast, there is a great deal of folklore but no consistent association of moon cycles with human physiology and behavior [3]. Here we show that subjective and objective measures of sleep vary according to lunar phase and thus may reflect circalunar rhythmicity in humans. To exclude confounders such as increased light at night or the potential bias in perception regarding a lunar influence on sleep, we retrospectively analyzed sleep structure, electroencephalographic activity during non-rapid-eye-movement (NREM) sleep, and secretion of the hormones melatonin and cortisol found under stringently controlled laboratory conditions in a cross-sectional setting. At no point during and after the study were volunteers or investigators aware of the a posteriori analysis relative to lunar phase. We found that around full moon, electroencephalogram (EEG) delta activity during NREM sleep, an indicator of deep sleep, decreased by 30%, time to fall asleep increased by 5 min, and EEG-assessed total sleep duration was reduced by 20 min. These changes were associated with a decrease in subjective sleep quality and diminished endogenous melatonin levels. This is the first reliable evidence that a lunar rhythm can modulate sleep structure in humans when measured under the highly controlled conditions of a circadian laboratory study protocol without time cues.
Keywords: Adult; Aged; Cross-Sectional Studies; Electroencephalography; Female; Humans; Hydrocortisone/analysis/metabolism; Male; Melatonin/analysis/metabolism; Middle Aged; Moon; Nontherapeutic Human Experimentation; Periodicity; Saliva/metabolism; Sleep/*physiology; Sleep Stages/physiology; Young Adult
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Gatford, K. L., Kennaway, D. J., Liu, H., Kleemann, D. O., Kuchel, T. R., & Varcoe, T. J. (2019). Simulated shift work disrupts maternal circadian rhythms and metabolism, and increases gestation length in sheep. J Physiol, 597(7), 1889–1904.
Abstract: KEY POINTS: Shift work impairs metabolic health, although its effects during pregnancy are not well understood We evaluated the effects of a simulated shift work protocol for one-third, two-thirds or all of pregnancy on maternal and pregnancy outcomes in sheep. Simulated shift work changed the timing of activity, disrupted hormonal and cellular rhythms, and impaired maternal glucose tolerance during early pregnancy. Gestation length was increased in twin pregnancies, whereas singleton lambs were lighter at a given gestational age if mothers were subjected to shift work conditions in the first one-third of pregnancy. Exposure to rotating night and day shifts, even if only in early pregnancy, may adversely affect maternal metabolic and pregnancy outcomes. ABSTRACT: Shift workers are at increased risk of developing type 2 diabetes and obesity; however, the impact during pregnancy on maternal metabolism is unknown. Using a large animal model, we assessed the impact of simulated shift work (SSW) exposure during pregnancy on maternal circadian rhythms, glucose tolerance and pregnancy outcomes. Following mating, ewes were randomly allocated to a control photoperiod (CON 12 h light, 12 h dark) or to SSW, where the timing of light exposure and food presentation was reversed twice each week for one-third, two-thirds or all of pregnancy. Maternal behaviour followed SSW cycles with increased activity during light exposure and feeding. Melatonin rhythms resynchronized within 2 days of the photoperiod shift, whereas peripheral circadian rhythms were arrhythmic. SSW impaired glucose tolerance (+29%, P = 0.019) and increased glucose-stimulated insulin secretion (+32%, P = 0.018) in ewes with a singleton fetus in early but not late gestation. SSW exposure did not alter rates of miscarriage or stillbirth, although it extended gestation length in twin pregnancies (+2.4 days, P = 0.032). Relative to gestational age, birth weight was lower in singleton progeny of SSW than CON ewes (-476 g, P = 0.016). These results have implications for the large number of women currently engaged in shift work, and further studies are required to determine progeny health impacts.
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Landers, J. A., Tamblyn, D., & Perriam, D. (2009). Effect of a blue-light-blocking intraocular lens on the quality of sleep. J Cataract Refract Surg, 35(1), 83–88.
Abstract: PURPOSE: To evaluate whether implantation of a blue-light-blocking intraocular lens (IOL) affects sleep quality. SETTING: Repatriation General Hospital, Adelaide, Australia. METHODS: This study comprised patients who had bilateral cataract surgery during the preceding 12 months with implantation of a conventional SI40NB IOL or an AcrySof Natural SN60WF blue-light-blocking IOL. Patients were contacted by telephone at least 6 months after second-eye surgery, and the Pittsburgh Sleep Quality Index (PSQI) questionnaire was administered. Results were compared between groups. RESULTS: Of the 49 patients, 31 received conventional IOLs and 18, blue-light-blocking IOLs. The mean age of the patients was 80 years +/- 8.1 (SD). The median PSQI score was 6 (interquartile range 3 to 8). There were no statistically significant differences in PSQI scores between the 2 IOL groups (P = .65). This remained true after adjustment for sex, age, medication, and time since surgery. CONCLUSION: The blue-light-blocking IOL had no effect on the sleep quality of patients, indicating that these IOLs might serve as an alternative to conventional IOLs without a detrimental effect on circadian rhythm.
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