Explore chapters and articles related to this topic
Biological Responses in Context
Published in Arthur T. Johnson, Biology for Engineers, 2019
Melatonin is produced in the pineal gland in the brain. There is a set of photoreceptors in the human eye that is distinct from the rods and cones responsible for vision; this third type of receptor senses light in the blue region and reports to the suprachiasmatic nucleus, which, in turn, prompts the pineal gland to make less melatonin if the level of blue light coming into the eye is higher. There is naturally more blue light in sunshine at noon, less at sunrise and sunset, and none at night. Hence, sleepiness associated with increased melatonin level is naturally keyed to the hours of darkness. Artificial light with significant amounts of blue light can interfere with this natural cycle.
Health effects of exposure to extremely low frequency fields
Published in Riadh Habash, BioElectroMagnetics, 2020
One area attracting attention as a likely potential mechanism for EM intervention in living organisms is consideration of a cancer-promoting effect of ELF fields by altered circadian rhythms of pineal activity and melatonin release. Melatonin is a hormone which is synthesized in the pineal gland in the brain. It regulates the human and animal circadian rhythm by a variation of its concentration. The “melatonin hypothesis”, first proposed many years ago, described how ELF field exposure is related to certain kinds of hormone-dependent cancers, particularly breast cancer.
Nonionizing Radiation
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Melatonin is produced by the pineal gland in a circadian rhythm, with levels higher at night and lower during the day. Exposure to light, to ELF fields, or to pulsed static magnetic fields can result in reduced levels of melatonin. Grota and colleagues observed a reduction in serum melatonin but not in pineal melatonin in rats exposed to ELF E fields, while others found no significant differences in melatonin levels. Some researchers have suggested that disruption of the melatonin circadian rhythm might be involved in female breast cancer and depression.
Around the world in 16 days: the effect of long-distance transmeridian travel on the sleep habits and behaviours of a professional Super Rugby team
Published in Journal of Sports Sciences, 2021
Tim D Smithies, Peter R Eastwood, Jennifer Walsh, Kevin Murray, Will Markwick, Ian C Dunican
There are potential limitations for the current study. Due to practical constraints, no subjective jet-lag ratings or physiological markers of circadian rhythm (salivary melatonin/ body temperature measures) were taken, which could have further demonstrated the presence of jet-lag for the players. These physiological measurements (particularly core body temperature) are widely used as indicators of the circadian phase and to demonstrate circadian adjustment and could have strengthened the reports of circadian adjustment suggested by the objective sleep measures here. While it was impractical to obtain physiological measures of circadian rhythm in the current study, the authors encourage future researchers to obtain these measures whenever possible. Additionally, there was no recording or controlling of sleep medication/ exogenous melatonin use throughout the study. Exogenous melatonin use can greatly affect the body clock, causing phase delay or phase advance depending on timing of use, and can be used to mitigate the effects of jet-lag (Waterhouse et al., 2007). Controlling such variables would result in a clearer understanding of the effects of LDTT alone on the human body, however results obtained would lose external validity for travelling professional sporting teams which may use such sleeping aids. Lastly, compliance issues resulted in missing data for some days, particularly on day 7; this was likely due to players forgetting to re-apply their actigraph device post-match.
Restricting short-wavelength light in the evening to improve sleep in recreational athletes – A pilot study
Published in European Journal of Sport Science, 2019
Melanie Knufinke, Lennart Fittkau-Koch, Els I. S. Møst, Michiel A. J. Kompier, Arne Nieuwenhuys
Sleep is considered indispensable for recovery and skill acquisition in athletes (Fullagar et al., 2015; Halson, 2008). Paradoxically, athletes show markers of poor sleep quality and sleep efficacy despite having sufficient opportunity to sleep (i.e. based on an approximation of 8:30 h of time spent in bed (TIB); Knufinke, Nieuwenhuys, Geurts, Møst, et al., 2018; Leeder, Glaister, Pizzoferro, Dawson, & Pedlar, 2012). Modern-technologies, such as smartphones and laptops, are often blamed for high-jacking sleep, particularly in adolescents and athletes who are susceptible to the ‘fear of missing out’ (Romyn, Robey, Dimmock, Halson, & Peeling, 2016). The effect is twofold; The psychological sleep threatening components concern the stimulating effect of media content associated with higher bedtime arousal and delayed bedtimes (Halson, 2016). Another, physiological, component which will be focused on in this study, concerns evening exposure to artificial light, especially short wavelength light, which is thought to delay circadian phase by suppressing habitual melatonin synthesis (Heath et al., 2014; West et al., 2011; Wood, Rea, Plitnick, & Figueiro, 2013). Melatonin is crucial for sleep initiation and maintenance in humans (Brainard et al., 2001). Given the significance of sleep as a means for recovery and skill acquisition in athletes (Bonnar, Bartel, Kakoschke, & Lang, 2018), the current study sought to determine whether reducing evening exposure to short-wavelength light can improve sleep among recreational athletes.
A review of the impact of shift-work on cancer: summary of the evidence for practitioners
Published in Policy and Practice in Health and Safety, 2018
John William Cherrie, Joanne O. Crawford, Alice Davis, Ken Dixon, Carla Alexander, Hilary Cowie, Damien Martin McElvenny
The most commonly suggested mechanism for an increased breast cancer risk in night workers is the suppression of melatonin by exposure to light at night. Melatonin is a hormone produced by the pineal gland in the brain that is associated with control of sleep–wake cycles (circadian rhythms). During the hours of darkness, melatonin levels in the blood rise to a peak at ∼3–4 am and then fall, so that by ∼9 am the blood concentration is negligible. When people are exposed to light at night melatonin production is reduced, weakening the circadian rhythm. Melatonin is known to have anti-carcinogenic properties—suppressing the proliferation of breast cancer cells, which is a possible mechanism by which cancer risk is increased when people are exposed to light at night. Other suggested putative mechanism include phase disruption where the sleep–wake cycle becomes adjusted to being awake at night, sleep disturbance, reduced synthesis of vitamin D because of lower exposure to sunlight for night workers and lifestyle factors for night workers such as poor diet resulting in obesity.