It is fundamentally clear to argue that maintaining an adequate sleep schedule is the key to regulating and maintaining individual health. As simple as it may seem to prioritize sleep, the underlying mechanism of the mammalian sleep-wake cycle has grave effects on virtually every aspect of preservation of health. Sleep operates under circadian rhythm, which is well defined as the periodic oscillations residing in a twenty-four hour cycle that regulates behavioral and biological patterns. Circadian rhythm is termed the “master clock” that systematically controls when an individual is awake and when they are asleep; and in mammals this clock occupies the suprachiasmatic nucleus of the anterior hypothalamic region, which relies on a subset of gene expressions to carry out sleep-wake functions.1 Though genes play a large role in regulating our sleep patterns, it does not serve as the sole explanation to how humans display sleep scheduling; on the contrary, behavioral aspects demand an equally important role. Though some may abide by a normal sleep schedule, a number of individuals, unfortunately, engage in activity that may alter their course of arousal such as night shift work, day time napping, excessive artificial light stimulation, etcetera. As Phyllis Zee states in her research article, “Circadian Disruption and Human Health,” disturbances to the alignment of sleep cause common measures that have been associated with adverse health conditions.1 So much so that circadian disruption, in form of misalignment or other implications, yields an increased vulnerability to obtaining neurologic, psychiatric, metabolic, cardiovascular, allergic, and immunologic disorders.1 Though it is not a definitive construct that circadian rhythm irregularities convey a causal effect of health disorders, it is evidently clear that the two share a bidirectional relationship. It is a central topic of discussion to further the understanding of this vastly immense study in which neuroscientists work to continue research like Phyllis’ in order to better comprehend treatment plans in an attempt to combat circadian disruption. Research studies such as Francesso Cappuccio, Kung Hu, Yue Leng, Erik Musiek, and Kristine Yaffe’s “Association Between Circadian Rhythms and Neurodegenerative Diseases” works to conceive a higher knowledge of how irregular sleep patterns may induce Alzheimer’s Disease and Parkinson's Disease.
Research has indicated that there is a bidirectional relationship between circadian disruption and neurodegeneration in that misalignment and decreased amplitude of rhythms has been shown to predict the development of neurologic diseases.1 A variety of correlations have been drawn between patients with neurodegenerative disorders and circadian disruption. For instance, patients with neurodegenerative diseases frequently experience circadian rhythm disruptions (CRD) in a much more severe form than typical age-related CRD, in that they become more active during the night, less active during the day, and sometimes have complete reversal or loss of the twenty-four hour rest-activity pattern.2 Though symptoms of difficulty falling asleep during the night and ease coming throughout the day comes naturally with aging, these symptoms are exacerbated in patients with moderate to severe Alzeheimers, in which degradation to the suprachiasmatic nucleus has been posed as a possible explanation. These individuals are recorded to have higher fragmentation, severely decreased amplitude, and phase delay.2 Although there may be some variability within research over this vastly complex topic, studies such as this show continuity with studies like that performed by Phyllis where she also documented similar findings, in which it contributes support that there is a tangible relationship between circadian disruption and neurodegenerative disorders. Additionally, behavior and biological factors heavily influence the function of genes that express circadian rhythm. Genes like CLOCK, which works to organize the phases of the sleep-wake cycle, and BMAL1, which works to regulate neurophysiological responses, are vulnerable to being manipulated through the severity and quantity of stimuli by processes of transcription and translation. Irregular sleep alignment and health implications alike may alter peptide dynamics and methylation, both of which can induce degradation of critical master clock genes which in turn affect the translation expression ultimately leading to circadian abnormalities. In fact, it was noted that BMAL1 promoter was described in fibroblasts from AD patients and in post-mortem AD brain samples, suggesting an underlying epigenetic mechanism of circadian disruption in AD.2 Notation like these and those discovered about individual sleep patterns serve as as significant indication that circadian disruption is both affected by behavioral and biological markers. Not only that, but it also contributes to evidence steering towards the statement that though circadian dysfunction and neurologic disorders share a bidirectional relationship, it is becoming progressively clear that disturbances to the sleep-wake cycle serve as a precursor to neurodegenerative diseases further down the line.
Research like that of the “Circadian Disruption and Human Health” by Phyllis Zee and “Association Between Circadian Rhythms and Neurodegenerative Diseases” by Erik Musiek et al., conduct vital experimentation and studies in order to discover the secret behind what potentially fuels neurodegeneration. The cases of moderate to severe Alzeheimer’s and other forms of dementia alike, are increasingly climbing at exponential rates among those about sixty-five years of age. Amongst these groups of people, African Americans are twice as likely to receive a form of dementia, and two-thirds of Americans with Alzeheimer’s are women. In a study of 11247 individuals in Sweden concluded that delayed rising time predicted dementia incidence after seventeen years of follow up; and in another study of 2920 individuals, it was reported that those who napped for approximately one hour a day doubled their vulnerability to developing Parkinson’s Disease after eleven years of follow up.2 With the unfortunate, amounting of dementia diagnoses, it is immensely important for research, like those previously stated, to uncover how factors such as circadian disruption may influence sleep-wake cycles in order to better understand how to effectively combat neurodegenerative disorders.
Works Cited
Fishbein, A. B., Knutson, K. L., & Zee, P. C. (2021). Circadian disruption and human health. Journal of Clinical Investigation, 131(19). https://doi.org/10.1172/jci148286
Leng Y, Musiek ES, Hu K, Cappuccio FP, Yaffe K. Association between circadian rhythms and neurodegenerative diseases. Lancet Neurol. 2019 Mar;18(3):307-318. doi: 10.1016/S1474-4422(18)30461-7. Epub 2019 Feb 12. PMID: 30784558; PMCID: PMC6426656.
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