Written by Quynh Do and Edited by Ashima Seth
Sleep is one of the fundamental necessities of life. We need it to function properly every day, and to strengthen our learning. But what happens when sleep becomes less of a priority and we begin depriving ourselves of sleep to do other tasks such as studying and partying?
Dr. Bryce A. Mander from the University of California, Irvine School of Medicine, has been conducting research on sleep for years. His research started on “The sleep-deprived human brain,” where he and his colleagues studied the effects of sleep deprivation and has lead to “Sleep: A Novel Mechanistic Pathway, Biomarker, and Treatment Target in the Pathology of Alzheimer’s Disease?”, where he and his colleagues further studied the pathology of sleep [1,2]. After decades of studying sleep, he has connected sleep deprivation to neuropathological issues such as Alzheimer’s disease (AD), one of the nation’s growing concerns. AD is defined as a type of dementia, or memory loss, which has the following symptoms: disorientation, mood changes, confusion, paranoia, behavior changes, and difficulties with speaking, swallowing and walking. What differentiates AD from other forms of dementia is that it is progressive and worsens over time. AD is usually common in older adults, but can also start as early as the age of 40. Unfortunately, no cure has been found for the disease as of yet [3].
Numerous research studies have been conducted on AD, but more research is needed to understand the factors of its progression in order to prevent the disease. Sleep disturbance and sleep disorders have been found to increase AD’s progression by increasing the accumulation of cerebrospinal fluid markers of next day β-amyloid (Aβ) and tau pathology, the defining pathologies of AD. Cerebrospinal fluid is a clear, colorless liquid found within the brain and the spinal cord (“cerebro” meaning related to the brain and “spinal” meaning relating to the spine). This fluid serves to circulate nutrients from the blood and filter waste from the brain. Markers, or indicators of the disease, help screeners diagnose the disease. Specifically speaking, Aβ plaques are biomarkers, markers within the body, for AD and are associated with disruption of normal brain function. These protein fragments hinder neural communication within the brain. Tau tangles are other biomarkers for AD and are associated with neurological decline. Tau is a protein that helps maintain microtubules, or the tubular structures in the structural skeleton of cells. The tangles diminish the health of neurons (brain cells) and cause higher neuronal loss [4]. Both Aβ and tau lead to the weakening of neural health within the brain and contribute to neurodegeneration.
At the UCI Center for Sleep and Circadian Neuroscience or Department of Psychiatry and Human Behavior, Dr. Mander and his team are researching how sleep affects neurological decline as we age. The brain is divided into regions called lobes. The medial temporal lobe is located within the center of the brain and is important for declarative memory, the type of memory associated with recalling facts and events. The research objective of Dr. Mander and his team is to clarify which aspects of sleep disturbance predict AD pathological (meaning “disease causing”) accumulation and spread, and which aspects track longitudinal change in medial temporal lobe (MTL) dysfunction and degeneration. Findings from their study thus far show that sleep loss is correlated with higher incidences of sleep disruption, which may hinder both rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep which are critical to neural growth. Both REM sleep and NREM sleep are the two main components of the sleep cycle. NREM sleep can be divided into three stages, all of which occur before REM sleep. REM sleep and NREM sleep have different vital functions for the brain. REM sleep is important for learning and protein production, while NREM sleep is important for repair and relaxation [5]. When an individual’s sleep cycle is disrupted in cases such as sleep disturbance, neural connectivity in his or her brain weakens, thus increasing susceptibility for developing neurodegenerative diseases such as AD.
Sleep deprivation has become a culture for college students. Whether it be from studying for an upcoming exam or binge-watching season after season of shows on Netflix, many students do not prioritize their sleep. However, several studies have shown the negative consequences of sleep loss including changes to brain activity, brain performance, attention, memory, and behavior [1]. If college students do not change these sleep-depriving habits, it could result in AD at an older age. A few words of advice from Dr. Mander: “Prioritize sleep even though it is very difficult, it is worth it” [6].
References
1. Krause, A.J., Simon, E.B., Mander, B.A., Greer, S.M., Saletin, J.M., Goldstein-Pierkarski, A.N., et al. (2017). The sleep-deprived human brain. Nature Reviews Neuroscience, 18: 404-418.
2. Mander, B.A., Winer, J.R., Jagust, W.J., Walker, M.P. (2016). Sleep: A Novel Mechanistic Pathway, Biomarker, and Treatment Target in the Pathology of Alzheimer’s Disease? Trends in Neuroscience, 39: 552-566.
3. “What Is Alzheimer’s?” Alzheimer’s Association, Alzheimer’s Association, http://www.alz.org/alzheimers-dementia/what-is-alzheimers
4. Sperling, R.A., Aisen, P.S., Beckett, L.A., Bennett, D.A., Craft, S., Fagan, A.M., et al. (2011). Toward defining the preclinical stages of Alzheimer’s disease: Recommendations from the National Institute on Aging-Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimer’s & Dementia, 7: 280-292.
5. Mander, B.A., Winer, J.R., Walker, M.P. (2017). Sleep and Human Aging. Neuron, 94: 19-36.
6. Mander, Bryce A. Personal interview. 19 Nov 2018.