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Sleep Length
Published in Clete A. Kushida, Sleep Deprivation, 2004
In a second study, long and short sleepers participated in a 40-hour constant routine protocol (39,40). A spectral analysis of waking EEG from this experiment showed that the short sleepers had increased power in the 5.25–9-Hz and the 17.25–18-Hz ranges. Increased time awake (i.e., sleep loss) was also associated with an increase in the 5.25–9-Hz range. These findings of increased theta with sleep loss and in short sleepers therefore also indicated that the short sleepers might have a greater sleep debt than the long sleepers. In the same study (40), blood samples were taken every 30 min to measure thyroid-simulating hormone (TSH) concentrations. TSH was significantly elevated in the short sleepers both prior to and during the sleep loss. Body temperature was also lower in the short sleepers. The authors interpret all of these findings as consistent with higher sleep pressure in the short sleepers. However, the effects of sleep deprivation on TSH and body temperature are open to some speculation. Total sleep loss typically results in an increase in TSH (42), usually associated with remaining awake longer. However, one study (43) has shown a decrease in TSH after partial sleep deprivation. Reports of body temperature change associated with total sleep deprivation are also variable.
Associations between chronotype, social jetlag, and weekday sleep in women with irritable bowel syndrome
Published in Chronobiology International, 2021
Pei-Lin Yang, Robert L. Burr, Horacio O. de la Iglesia, Diana T. Buchanan, Teresa M. Ward, Carol A. Landis, Margaret M. Heitkemper
In conclusion, our findings show that women with IBS-D experience more disrupted sleep across weekdays and weekends compared to healthy control women. The findings also indicate that chronotype may be an important contributor to weekday sleep outcomes for all women with and without IBS, whereas SJL is not. The direction of the association between chronotype and weekday sleep outcomes is influenced by IBS bowel pattern predominance subgroups. Disrupted sleep and inappropriate sleep practices are treatable through addressing sleep behavioral strategies and/or potential chronotherapy. Future research needs to validate our preliminary evidence about chronotype and SJL as well as their relationships, potentially incorporating physiological biomarkers and other measures of behavioral and environmental cues for circadian pattern on a constant routine protocol.
Systematic review of melatonin levels in individuals with complete cervical spinal cord injury
Published in The Journal of Spinal Cord Medicine, 2020
Alexander Whelan, Mary Halpine, Sean D. Christie, Sonja A. McVeigh
The evidence owes much to the high-quality study conducted by Zeitzer et al.41 The strength of their study relates to the utilization of a constant routine protocol. Individuals were subjected to 46 h of wakefulness in a constant posture, with stable dim light conditions and room temperatures, with meals and fluids provided on an hourly basis to ensure that participants received their typical caloric intake over a 24-h period. The basis of the constant routine is to mask periodic changes in behavior – such as sleep, posture, food intake, temperature, and physical activity level – that may interfere with circadian rhythms.55,56 Besides the use of a constant routine, Zeitzer et al. created strict exclusion criteria that eliminated confounding variables such as recent substance use, phase-shift influences and other neurological injury.41 The administration of a constant routine may explain why Zeitzer et al. demonstrated undetectable melatonin levels in individuals with complete cervical SCI, unlike the other studies which reported reduced, but present, night-time levels.41 By controlling environmental inputs, the constant routine may have eliminated factors that triggered non-cervical spinal cord mediated melatonin production. The issue with the constant protocol is that it is time-intensive, demands sleep deprivation from its participants and requires an environment suitable for controlling temperature and light conditions, which is difficult to apply in standard hospital and home settings.55,56
Temperature regulation in women: Effects of the menstrual cycle
Published in Temperature, 2020
Fiona C. Baker, Felicia Siboza, Andrea Fuller
Core body temperature has an endogenously generated circadian rhythm with a period close to 24-h, which is evident even when environmental conditions are kept constant, free of influences from sleep-wake patterns, activity, meals, or light exposure [18,19]. In such constant conditions (i.e., a constant routine protocol), subjects undergo a regime of semi-recumbent wakefulness in dim light while energy intake is controlled [20]. The core body temperature curve recorded under constant conditions is one of the gold standard methods to quantify or demonstrate circadian phase, or the output of the central clock (along with melatonin). Core body temperature continues to oscillate independently of other physiological rhythms or external time cues between a maximum in the active period (daytime for humans) and a minimum during the inactive period (nocturnal for humans), with an amplitude of 0.8°C to 1.0°C [21]. A cosinor curve can be fitted to the rhythm in order to determine its circadian mesor (average temperature across 24 h), phase (time of maximum temperature [acrophase], or time of minimum temperature [nadir]) and amplitude (mesor – minimum temperature). Both heat production and heat loss contribute to the circadian variation in heat content, leading to a circadian rhythm in core body temperature [22]. Indeed, under constant conditions, the circadian rhythms in heat production (measured with indirect calorimetry) and distal skin (hands and feet) temperature, reflecting heat loss, are phase-advanced relative to that of core body temperature [22].