Page 98 - Journal of Special Operations Medicine - Spring 2016

evidence that sleep is involved in converting new infor- Finally, overwhelming evidence confirms that inade-
mation from short-term into long-term memory over quate sleep results in adverse health outcomes. Extreme
the course of attempting to master a complex skill. cases of insufficient sleep have been linked to metabolic
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Thus, over time, if one is trying to learn a new skill and syndrome, 21,22 impaired immune function, cardiovas-
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not getting enough sleep on a regular basis, it may be cular disease, type 2 diabetes, and even mortality. 26,27
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very difficult to master that particular skill. Moreover,
insufficient sleep leads to impaired alertness and perfor- Although limited evidence indicates that getting more
mance that will accrue across the days and weeks of too sleep actually improves health, sufficient sleep is clearly
little sleep. 11,12 These impairments for new learning and linked to better cognitive performance outcomes includ-
reductions in cognitive performance can greatly impact ing faster performance on vigilance tasks and fewer
a leader or individual’s ability to effectively do their job lapses in attention, 28,29 as well as increased vigor
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and thereby reduce the likelihood of mission success or and better physical performance. Specifically, scien-
of accomplishing the intended goal. tific evidence suggests that athletic performance can
be improved by extending sleep (8–10 hours in bed) at
Of particular military relevance is the link between the night. 31,32
experience of stress and decreased cognitive function.
Specifically, stress endured during combat-like train- Beyond cognitive and physical performance, emotional
ing (e.g., US Navy SEAL training) has been shown to and social functioning are impacted by the amount of
negatively impact all cognitive functions, from simple sleep a person gets each night. Getting 8 hours of sleep
reaction time and vigilance to complex functions like increases optimistic outlook and social functioning,
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memory and logical reasoning. Insufficient sleep is an whereas those who are chronically sleep restricted have
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extreme stressor, and when combat stressors are cou- reduced resilience to stress-related disorders such as
pled with periods of insufficient sleep, the negative ef- posttraumatic stress disorder and depression. 34–38
fects on performance and mission success are likely to
be compounded. Individuals are typically unaware of the extent to which
their performance is compromised by lack of sleep. Im-
Sleep loss also affects the efficiency of many bodily pro- portantly, physiologic measures of adaptation across
cesses and the ability to use or store energy, which can numerous studies indicate it is impossible to adjust to
result in a reduced capacity to meet demands of effort or train for chronic sleep restriction. 39,40 Not only are
and overall performance decrements (Table 1). (For a individuals bad judges of how lack of sleep affects them,
comprehensive review of these physiological effects, they are also poor at reporting how much sleep they
see Engle-Friedman. ) Additionally sleep loss impairs actually get. In fact, after experiencing continual sleep
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the body’s ability to regulate temperature. A number restriction or deprivation, people become so used to it,
of studies have shown that sleep loss and generalized that they might think they do not need more sleep. They
fatigue, in particular, are among the most common pre- are wrong, and this lack of insight occurs because areas
disposing factors for exertional heat stroke. 15–18 Thus, of the brain (e.g., prefrontal cortices) needed to make
insufficient sleep can compromise mission success by its an accurate assessment of their abilities are impaired by
potential to increase the risk of exertional heat illness. sleep loss. Because self-report of sleep loss does not al-
ways accurately reflect the actual level of impairment,
Table 1 Selected Performance-Degrading Effects of objective measures of sleep (e.g., wrist actigraphy) are
Insufficient Sleep critical for evaluating both individual and unit-level
Increases likelihood of accidents readiness, especially in operational environments where
Compromises vigilance, decision-making, and performance is critical to mission success. Actigraphy is
critical thinking a valuable tool to use in conjunction with a fatigue risk-
Increases risk for heat stroke management system for monitoring alertness in various
high-risk and shift-work environments, including avia-
Enhances symptoms of pain, fatigue, and negative mood tion, 41,42 trucking, and hospitals. 44
43
Reduces resilience to stress-related disorders
Individuals are not immune to the effects of sleep loss.
Chronic insufficient sleep is also related to increased ex- Furthermore, during periods of extended wakefulness,
perience of pain (e.g., body pain, back pain, stomach the decrementing effects of sleep loss cannot be reversed
pain ), which also may reduce performance. In addi- by physical exercise, work breaks, posture, or physical
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tion, some injuries sustained during physical training fitness. As it stands right now, the only way to prepare
(PT), like musculoskeletal injuries (stress fractures), are for periods of insufficient sleep or to effectively reverse
preventable through improved PT, whereas others may the effects of sleep loss is to get more sleep. Extending
require sleep modifications to avoid or mitigate injury. 20 sleep prior to periods of sleep loss can help to maintain

82 Journal of Special Operations Medicine Volume 16, Edition 1/Spring 2016