Why We Sleep - Parts One & Two Summary
Part one of Why We Sleep closes with a summary of how sleep patterns change with age. Babies and young children exhibit polyphasic sleep, where they sleep in small doses throughout the day and night compared to older children and adults who have more regular monophasic sleep. As humans age, there is also a decrease in the amount of time spent in REM sleep and an increase in NREM sleep. This pattern highlights the importance of NREM sleep as a driver of brain maturation. Unfortunately, for many seniors the ability to achieve deep NREM sleep is impaired despite little change in the requirement for deep NREM sleep. The loss of deep NREM sleep is associated with many of the memory issues seen in older individuals and many times the pathology caused by a decrease in sleep quality is misattributed to other issues such as the onset of dementia.
In part two, “Why Should You Sleep?,” Dr. Walker summarizes the many benefits of sleep and details the detrimental effects of sleep deprivation. Sleep is essential for learning and the consolidation of memory. Many studies have shown that sleeping after a memorization task increases retention rates. Beyond memorization, sleep is also necessary for motor learning, commonly referred to as “muscle memory.” During the last two hours of sleep, sleep spindles increase above the motor cortex during NREM sleep leading to a solidification of motor skills learned during the day. Although important for everyone, this sleep stage is especially essential for athletes but remains a generally overlooked aspect of athletic training.
As much as sleep can improve your health, sleep deprivation has equally negative health effects. The impacts of poor sleep can occur after a single night of reduced sleep and many people fail to recognize their own chronic sleep deprivation. Many psychiatric disorders are associated with poor sleep and although the causal relationship between the two isn’t fully understood, there is likely a two way relationship. A rise in chronic disorders such as heart disease, high blood pressure and obesity in the United States has been correlated with a decrease in the average length of sleep per night. There are mechanistic explanations for the correlation of poor sleep with many chronic diseases including altered food choices following poor sleep, increased sympathetic nervous system activation and altered gene expression profiles.
Andi DeRogatis is a graduate student at UC Davis in the animal biology graduate group. She is currently studying how the avian immune system is influenced by the process of molt. She loves all things birds and is passionate about getting others excited about birds as well! You can follow her on Twitter @AndiDerogatis.
Lindsey Mooney is a graduate student in the UC Davis Psychology Department. You can follow her on Twitter @Linz_Mooney.