The Circadian Code: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight

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unreliable medical source?] Regestein QR, Pavlova M (September 1995). "Treatment of delayed sleep phase syndrome". General Hospital Psychiatry. 17 (5): 335–345. doi: 10.1016/0163-8343(95)00062-V. PMID 8522148. Delezie J, Dumont S, Dardente H, Oudart H, Gréchez-Cassiau A, Klosen P, etal. (August 2012). "The nuclear receptor REV-ERBα is required for the daily balance of carbohydrate and lipid metabolism". FASEB Journal. 26 (8): 3321–3335. doi: 10.1096/fj.12-208751. PMID 22562834. S2CID 31204290. Ikeno, T. & Yan, L. Chronic light exposure in the middle of the night disturbs the circadian system and emotional regulation. J. Biol. Rhythms 31, 452–464 (2016). Arushanyan, E. B. & Popov, A. V. Influence of damage to the suprachiasmatic nuclei of the hypothalamus of rats on the dynamics of short-period fluctuations of normal and abnormal behavior. Neurosci. Behav. Physiol. 25, 290–295 (1995).

Circadian: relating to biologic variations or rhythms with a frequency of 1 cycle in 24 ± 4 h; circa (about, approximately) and dies (day or 24 h). Note: term describes rhythms with an about 24-h cycle length, whether they are frequency-synchronized with (acceptable) or are desynchronized or free-running from the local environmental time scale, with periods of slightly yet consistently different from 24-h. [19] Most of the evidence supporting the effects of atypical light exposure on affective responses has been gleaned from animal models, particularly rodents, because of the ease with which light exposure can be controlled. One advantage of using rodents is that the most common lab species are nocturnal, and so exposure to light at night occurs during their active and awake phase. Thus, light at night does not directly alter sleep in nocturnal species. This is important because most effects of disrupted circadian rhythms on human mood are attributed to sleep disruption, but studies using nocturnal species demonstrate that this is not the only cause as sleep remains intact when animals are exposed to dim light at night 56. Studies of light at night exposure in diurnal rodent species generally yield similar affective responses to nocturnal rodents 57, 58. Another important difference between humans and individuals of some rodent species is the production of pineal melatonin. Although both nocturnal and diurnal species produce melatonin during the dark phase, several common laboratory strains of mice have no detectable pineal melatonin rhythms. Nonetheless, studies using Swiss Webster mice (which have no detectable pineal melatonin) vs. Siberian hamsters (which have a robust pineal melatonin rhythm) have reported similar effects of light at night on affective responses 33, 59, 60, 61. This observation suggests that suppressed melatonin by nighttime light is not the only or even primary mechanism, but still may be an important contributor in humans and a potential point of intervention. Robillard, R. et al. Parallel changes in mood and melatonin rhythm following an adjunctive multimodal chronobiological intervention with agomelatine in people with depression; a proof of concept open label study. Front. Psychiatry 9, 624 (2018).

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Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at roughly 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers. However, newer research indicates that the melatonin offset may be the more reliable marker. Benloucif et al. [89] found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum. They found that both sleep offset and melatonin offset are more strongly correlated with phase markers than the onset of sleep. In addition, the declining phase of the melatonin levels is more reliable and stable than the termination of melatonin synthesis. Antle MC, Silver R (November 2009). "Neural basis of timing and anticipatory behaviors". The European Journal of Neuroscience. 30 (9): 1643–1649. doi: 10.1111/j.1460-9568.2009.06959.x. PMC 2929840. PMID 19878281. a b c Logan RW, Williams WP, McClung CA (June 2014). "Circadian rhythms and addiction: mechanistic insights and future directions". Behavioral Neuroscience. 128 (3): 387–412. doi: 10.1037/a0036268. PMC 4041815. PMID 24731209. In 2017, Jeffrey C. Hall, Michael W. Young, and Michael Rosbash were awarded Nobel Prize in Physiology or Medicine "for their discoveries of molecular mechanisms controlling the circadian rhythm". [160] [161] Danchin A. "Important dates 1900–1919". HKU-Pasteur Research Centre. Archived from the original on 2003-10-20 . Retrieved 2008-01-12.

Vos, T. et al. Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet 390, 1211–1259 (2017). Foster, R. G. et al. Sleep and circadian rhythm disruption in social jetlag and mental illness. Prog. Mol. Biol. Transl. Sci. 119, 325–346 (2013). Seizer L, Cornélissen-Guillaume G, Schiepek GK, Chamson E, Bliem HR and Schubert C (2022) About-Weekly Pattern in the Dynamic Complexity of a Healthy Subject's Cellular Immune Activity: A Biopsychosocial Analysis. Front. Psychiatry 13:799214. doi: 10.3389/fpsyt.2022.799214 The Arabidopsis with the 24-hour circadian cycle was grown in three different environments. [65] One of these environments had a 20-hour light and dark cycle (10 hours of light and 10 hours of dark), the other had a 24-hour light and dark cycle (12 hours of light and 12 hours of dark),and the final environment had a 28-hour light and dark cycle (14 hours of light and 14 hours of dark). [65] The two mutated plants were grown in both an environment that had a 20-hour light and dark cycle and in an environment that had a 28-hour light and dark cycle. [65] It was found that the variety of Arabidopsis with a 24-hour circadian rhythm cycle grew best in an environment that also had a 24-hour light and dark cycle. [65] Overall, it was found that all the varieties of Arabidopsis thaliana had greater levels of chlorophyll and increased growth in environments whose light and dark cycles matched their circadian rhythm. [65]Tapia-Osorio, A., Salgado-Delgado, R., Angeles-Castellanos, M. & Escobar, C. Disruption of circadian rhythms due to chronic constant light leads to depressive and anxiety-like behaviors in the rat. Behav. Brain Res. 252, 1–9 (2013). a b Duffy JF, Cain SW, Chang AM, Phillips AJ, Münch MY, Gronfier C, etal. (September 2011). "Sex difference in the near-24-hour intrinsic period of the human circadian timing system". Proceedings of the National Academy of Sciences of the United States of America. 108 (Supplement_3): 15602–8. Bibcode: 2011PNAS..10815602D. doi: 10.1073/pnas.1010666108. PMC 3176605. PMID 21536890. Gooley, J. J. et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J. Clin. Endocrinol. Metab. 96, E463–E472 (2011). Young, D. M. Psychiatric morbidity in travelers to Honolulu, Hawaii. Compr. Psychiatry 36, 224–228 (1995). Nakano S, Uchida K, Kigoshi T, Azukizawa S, Iwasaki R, Kaneko M, Morimoto S (August 1991). "Circadian rhythm of blood pressure in normotensive NIDDM subjects. Its relationship to microvascular complications". Diabetes Care. 14 (8): 707–711. doi: 10.2337/diacare.14.8.707. PMID 1954805. S2CID 12489921.

Muehlbach, M. J. & Walsh, J. K. The effects of caffeine on simulated night- shift work and subsequent daytime sleep. Sleep 18, 22–29 (1994). Another gene that has been implicated in both SZ and circadian organization is immediate early gene growth response 3 ( Egr3) 162, 165, 166, 167, 168. Additional support for this candidate gene is provided by Egr3-deficient mice (−/−), which display behaviors that are reminiscent of SZ and sleep less than WT controls, even though the circadian organization of the sleep-wake cycle remained intact 169. Circadian rhythmicity is present in the sleeping and feeding patterns of animals, including human beings. There are also clear patterns of core body temperature, brain wave activity, hormone production, cell regeneration, and other biological activities. In addition, photoperiodism, the physiological reaction of organisms to the length of day or night, is vital to both plants and animals, and the circadian system plays a role in the measurement and interpretation of day length. Timely prediction of seasonal periods of weather conditions, food availability, or predator activity is crucial for survival of many species. Although not the only parameter, the changing length of the photoperiod (day length) is the most predictive environmental cue for the seasonal timing of physiology and behavior, most notably for timing of migration, hibernation, and reproduction. [44] Effect of circadian disruption [ edit ] Knapen, S. E. et al. Social jetlag and depression status: results obtained from the Netherlands Study of Depression and Anxiety. Chronobiol. Inter 35, 1–7 (2018).The rhythm has an endogenous free-running period that lasts approximately 24 hours. The rhythm persists in constant conditions, i.e. constant darkness, with a period of about 24 hours. The period of the rhythm in constant conditions is called the free-running period and is denoted by the Greek letter τ (tau). The rationale for this criterion is to distinguish circadian rhythms from simple responses to daily external cues. A rhythm cannot be said to be endogenous unless it has been tested and persists in conditions without external periodic input. In diurnal animals (active during daylight hours), in general τ is slightly greater than 24 hours, whereas, in nocturnal animals (active at night), in general τ is shorter than 24 hours. Kosmadopoulos A, Sargent C, Darwent D, Zhou X, Dawson D, Roach GD (December 2014). "The effects of a split sleep-wake schedule on neurobehavioural performance and predictions of performance under conditions of forced desynchrony". Chronobiology International. 31 (10): 1209–17. doi: 10.3109/07420528.2014.957763. PMID 25222348. S2CID 11643058. The SCN takes the information on the lengths of the day and night from the retina, interprets it, and passes it on to the pineal gland, a tiny structure shaped like a pine cone and located on the epithalamus. In response, the pineal secretes the hormone melatonin. [82] Secretion of melatonin peaks at night and ebbs during the day and its presence provides information about night-length. National Sleep Foundation. 2014 Sleep in America Poll. (National Sleep Foundation, Arlington, VA, 2014). Rusting, C. L. & Larsen, R. J. Diurnal patterns of unpleasant mood: associations with neuroticism, depression, and anxiety. J. Pers. 66, 85–103 (1998).