Sleep Deprivation, Cognitive Performance and Health Consequences
Len Kravitz, Ph.D.
Exercise professionals regularly design multifaceted cardiorespiratory and resistance training programs for clients. Healthy lifestyle educational tips and proper nutrition choices are essential discussions for clients hoping to realize the optimal health benefits from adherence to these exercise programs. However, many personal trainers work with clients in health fields, technology, security, computer operations, clinical lab occupations and transportation professions which require working at night. As well, issues such as the poor economy and economic conditions are leading more people to work longer hours. All of these professions and conditions can may lead to impaired sleep and sleep patterns, leading to compromised cognitive performance and health consequences. This article will describe the types and stages of sleep and discuss the deleterious effects of sleep deprivation on cognitive performance and health.
What are the Main Types and Stages of Sleep?
The two main types of sleep are Rapid Eye Movement (REM) and Non-REM sleep (which consists of four stages) (WebMD, 2010). During the night sleep patterns repeat cyclically, moving sequentially through 4 stages of non-REM sleep into REM sleep. REM sleep, which is about 20% of total sleep, initially lasts about 10 minutes and lengthens each repeating cycle, lasting up to an hour in the last phase (WebMd, 2010). During REM sleep the eyes move back and forth rapidly and the body's muscular contraction activity is minimal. Keenly remembered and very visual dreams occur during REM sleep. Heart rate and blood pressure increase while breathing rate becomes irregular and shallow during REM sleep. Interestingly, REM sleep is increased when people learn a new task, while REM sleep deprivation will interfere with the learning process (Hobson)
Non-REM sleep, which has 4 stages, is characterized by having less emotional and fewer visual impression dreams, as compared to REM sleep. Stage 1 is the transition to sleep which lasts about 5 minutes. This often feels like going into and out of sleep. Stage 1 is also where a person experiences sudden jerky movements or muscle twitches, referred to as hypnic myoclonic jerks (WebMD, 2010). Stage 2 of Non-REM sleep lasts for about 10 to 25 minutes. During this 'light sleep' stage the heart rate slows down, the body temperature decreases and brain wave activity slows down as the body prepares for deeper sleep. Stage 3 of non-REM sleep is often referred to as the first stage of deep sleep. It is during this stage that it is difficult to awaken a person and if awakened, the individual will feel disoriented for several minutes. During stage 3 brain wave activity alternates with a combination of slow and fast wave activity, and blood flow is directed away from the brain to other parts of the body for restorative function. Stage 4 is the deepest state of sleep. Brain wave activity is mostly slow delta waves, which are the brain's slowest frequency waves (beta, alpha and theta are the other wave categories).
What is Sleep Deprivation?
Most adults need about 7 to 8.5 hours of sleep each day (Aloha & Polo-Kantola, 2007). Aloha and Polo-Kantola continue that sleep serves as a restorative process for energy resources, tissue recovery, thermoregulation and cognitive function. Sleep deprivation is the study of the effects of sleep loss. In acute sleep loss research, subjects are kept awake continuously, generally for 24-72 hours. In chronic sleep deprivation research subjects have restricted sleep time over the course of several consecutive nights. Chronic sleep deprivation is more common and associated to real life conditions. Chronic sleep loss will activate the body's sympathetic nervous system, which can lead to an increase in blood pressure and cortisol secretion (Aloha &Polo-Kantola). Cortisol has been shown to stimulate appetite activate lipoprotein lipase, the enzyme that facilitates the deposition of fat, thus leading to weight gain (Bjorntorp, 2001). Aloha & Polo-Kantola add that immune function may be impaired
Sleep and Cognitive Performance
Chronic and acute sleep deprivation will negatively impact learning and thinking. There is a loss attention and alertness (Kilgore, 2010), which Aloha and Polo-Kantola (2007) explain involves a series of lapses, or slowed responses leading to waking-state instability in several cognitive processes such as working memory. Kilgore adds that sleep loss appears to affect some aspects of cognition more than others. For instance, creative and innovative mental processing appear to be much more negatively impaired as compared to decision making and planning tasks (Kilgore, 2010). Alhola and Polo-Kantola summarize other cognitive skills depressingly impaired from acute sleep loss such as reaction time, memory assignments, visuomotor tasks and reasoning skills.
Side Bar 1. Signs of Sleep Deprivation
The signs of sleep deprivation are often subtle and include many of the following:
Sleepiness in meetings, lectures or warm rooms
Lack of motivation
Irritability and moodiness
Need a nap to get through the day
Have a hard time getting out of bed
Rely too much on the snooze button
Reduced ability to cope and deal with stress
Frequent colds and infections
Difficulty concentrating
Memory problems
Feel sluggish in the afternoon
Drowsiness when driving
Weight gain
Impaired motor skills
Source:
Helpfulguide.org, Accessed November 22, 2011
http://helpguide.org/life/sleeping.htm
Myth 1: Getting just 1 hour less sleep per night won't affect your daytime functioning. You may not be noticeably sleepy during the day. But even slightly less sleep can affect your ability to think properly and respond quickly, and compromise your cardiovascular health, energy balance, and ability to fight infections.
Myth 2: Your body adjusts quickly to different sleep schedules. Most people can reset their biological clock, but only by appropriately timed cues-and even then, by 1-2 hours per day at best. Consequently, it can take more than a week to adjust after traveling across several time zones or switching to the night shift.
Myth 3: Extra sleep at night can cure you of problems with excessive daytime fatigue. Not only is the quantity of sleep important but also the quality of sleep. Some people sleep 8 or 9 hours a night but don't feel well rested when they wake up because the quality of their sleep is poor.
Myth 4: You can make up for lost sleep during the week by sleeping more on the weekends. Although this sleeping pattern will help relieve part of a sleep debt, it will not completely make up for the lack of sleep. Furthermore, sleeping later on the weekends can affect your sleep-wake cycle so that it is much harder to go to sleep at the right time on Sunday nights and get up early on Monday mornings.
Adapted from: Your Guide to Healthy Sleep (PDF) The National Institutes of Health
Resources:
Bjorntorp, P. (2001). Do stress reactions cause abdominal obesity and comorbidities? Obesity Reviews, 2, 73-86.
Killgore, W.D. (2010). Effects of sleep deprivation on cognition.Progress in Brain Research. 185:105-129.
Aloha, P. & Polo-Kantola, P. (2007). Sleep deprivation: Impact on cognitive performance. Journal of Neuropsychiatric Disease and Treatment, 3(5): 553-567.
WebMD:Accessed 11-22-11
http://www.webmd.com/sleep-disorders/excessive-sleepiness-10/sleep-101
Sleep Deprivation, Cognitive Performance and Health Consequences |
| What are the Main Types and Stages of Sleep? |
| The signs of sleep deprivation are often subtle and include many of the following: |
| Sleepiness in meetings, lectures or warm rooms |
| Lack of motivation |
| Irritability and moodiness |
| Need a nap to get through the day |
| Have a hard time getting out of bed |
| Rely too much on the snooze button |
| Reduced ability to cope and deal with stress |
| Frequent colds and infections |
| Difficulty concentrating |
| Memory problems |
| Feel sluggish in the afternoon |
| Drowsiness when driving |
| Impaired motor skills |
Helpfulguide.org, Accessed November 22, 2011
Resources:
Bjorntorp, P. (2001). Do stress reactions cause abdominal obesity and comorbidities? Obesity Reviews, 2, 73-86.
Killgore, W.D. (2010). Effects of sleep deprivation on cognition.Progress in Brain Research. 185:105-129.
Aloha, P. & Polo-Kantola, P. (2007). Sleep deprivation: Impact on cognitive performance. Journal of Neuropsychiatric Disease and Treatment, 3(5): 553-567.
WebMD:Accessed 11-22-11
http://www.webmd.com/sleep-disorders/excessive-sleepiness-10/sleep-101
|
|
