Page 108 - JSOM Winter 2022

TABLE 3 Self-Reported Sleep Measures of US Army Rangers With FIGURE 3 Self-reported musculoskeletal injury incidence by self-
and Without a Self-Reported Current MSI 45 reported hours of sleep among Special Operation Forces Soldiers
(Operators and support staff). 13
Reported No Reported
MSI MSI Difference p-value
Measure (mean ± SD) (mean ± SD) (%) (t-test)
Pittsburg Sleep
Quality Index 6.7 ± 3.7 4.5 ± 2.7 32.8 0.01
(0–21 scale)
Subjective
Sleep Quality 50.8 ± 17.5 68.9 ± 18.3 35.6 <0.01
(0–100 scale)
Insomnia
Severity Index 10.9 ± 3.7 7.2 ± 4.1 33.9 <0.01
(0–28 scale) a
Sleep Duration 6.1 ± 1.0 6.5 ± 0.9 6.6 0.10
(hours) 95% CI = 95% confidence interval
MSI = musculoskeletal injury, SD = standard deviation, US = United
States with higher self-reported sleep quality, less daytime sleepiness,
a The Insomnia Severity Index is a 7-item questionnaire that quantifies and better overall health outcomes. 70–75
perceived insomnia severity over the last two weeks. Higher scores
indicate more severe insomnia (≥15 indicates clinical insomnia).
Mitigating the Effects of Sleep Loss
FIGURE 2 Injuries in Chinese basic training by self-reported pre-
training sleep quality on the Pittsburg Sleep Quality Index. 44 Military personnel are often in extreme/harsh environments
with unpredictable schedules and limited resources. 61,76 It is
thus understandable that optimizing the sleeping environ-
ment can be challenging, and methods to mitigate the effects
of suboptimal sleep need to be considered. Several of these
methods have been investigated, although their effects on
subsequent MSI are not known. Mitigation strategies include
sleep banking, napping, and judicious use of caffeine and the
drug, modafinil.

Sleep Banking
Sleep banking is defined as extending the amount of time in
Low sleep quality was defined as a global Pittsburg Sleep Quality In- bed to get more sleep. Sleep banking has been shown to im-
77
dex score ≥7 for the Chinese population. 47 prove objectively measured vigilance and motor performance,
Inj = injury, OA = osteoarticular, RR = risk ratio, 95% CI = 95% as well as subjectively measured mood, alertness, and moti-
confidence interval
vation. 78–80 Importantly, sleep banking prior to sleep restric-
and shorter durations of most stages of sleep. Lower air tem- tion has been shown to improve performance on vigilance and
peratures with bedding adequate to maintain a stable thermal psychomotor performance tasks during periods of subsequent
microclimate around the body is associated with higher qual- sleep restriction. 77,81,82 For example, in one study a group was
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ity sleep. Use of media devices near bedtime and/or having assigned to spend 10 hours of time in bed while another group
media devices (e.g., cell phones, computers, gaming consoles) spent their usual time in bed (approximately seven hours) for
77
in the sleeping environment has been associated with poor a one-week period. This was followed by one week of three
sleep quality, increased daytime dysfunction, and excess day- hours sleep per night, then five days of recovery sleep (eight
time sleepiness. 62,63 Media devices may disrupt sleep either by hours/night). The group that sleep-banked demonstrated
displacing, delaying, or interrupting sleep, by the stimulating higher performance on a vigilance task during the sleep re-
effects of the media content, and/or by the light from the de- striction period and performance was also much higher during
vices influencing thermoregulation, circadian rhythms, and the recovery sleep phase. Thus, getting more sleep prior to a
mood. 62,63 Cell phones or other electronic devices in the sleep period of reduced sleep can be a potential way to improve
environment may be necessary, but should be set to receive vigilance and motor performance. Military personnel should
only important messages or calls. consider this when they anticipate performing a mission in-
volving periods of limited sleep.
Noise has been shown to delay sleep onset, increase awaken-
ings, reduce sleep efficiency, and reduce the amount of REM Napping
sleep. 64–66 Based on a total of eight systematic reviews, the Studies have shown that short naps improve both cognitive and
World Health Organization suggested that the average night motor performance, short term memory, and mood states. 83–85
noise should not exceed 45 decibels, which is roughly the sound Daytime napping in the afternoon between 1300 and 1600
of a quiet residential street. In research conducted in noisy en- hours seems most effective since this is the time of maximum
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vironments (hospital intensive care units), ear plugs have been daytime circadian sleepiness. Naps of all durations (5–120
shown to improve sleep quality, although many published stud- minutes) have benefits, but immediately following long naps
ies combined ear plugs with light-reducing eye masks. 68,69 (>30 minutes) sleep inertia may interfere with some types of
task performances and cognition. 83,85,86 Sleep inertia is grog-
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Being on a regular sleep-wake schedule is also important. Going giness, sleepiness, and disorientation felt upon awakening.
to bed and getting up at a regular times have been associated Nonetheless, a recent systematic review of studies involving
106 | JSOM Volume 22, Edition 4 / Winter 2022