Page 104 - JSOM Winter 2022

An Ongoing Series

Sleep and Injuries in Military Personnel
With Suggestions for Improving Sleep and
Mitigating Effects of Sleep Loss

Joseph J. Knapik, ScD *; John A. Caldwell, PhD ; Bradley M. Ritland, PhD 3
2
1

ABSTRACT
Sleep professionals suggest adults should sleep at least seven years of age should sleep at least seven hours per night on a
hours per night and define good sleep quality as 1) sleep onset regular basis to promote optimal health. 8, 9
≤15 minutes, 2) one or fewer awakenings per night, 3) awake
after sleep onset ≤20 minutes, and 4) sleep efficiency (ratio of While the duration of sleep is important for health, sleep qual-
sleep time to time in bed) ≥85%. This paper focuses on associ- ity is also critical. The National Sleep Foundation assembled
ations between injuries and sleep quality/duration among mil- an expert panel to objectively define sleep quality. The panel
itary personnel and strategies to optimize sleep and mitigate evaluated 12 measures of sleep quality shown and defined in
effects of sleep loss. Investigations among military personnel Table 1. Consensus was reached with good sleep quality de-
generally used convenience samples who self-reported their in- fined as sleep onset ≤15 minutes, one or fewer awakenings per
jury and sleep quality/quantity. Despite these limitations, data night, awake after sleep onset ≤20 minutes, and sleep efficiency
suggest that lower sleep quality or duration is associated with (ratio of sleep time to time in bed) ≥85%. Poor sleep quality
higher risk of musculoskeletal injury (MSI). Possible mech- was defined as sleep efficiency ≤64%, sleep latency >60 min-
anisms whereby poor sleep quality/duration may influence utes, awake after sleep onset ≥51 minutes, and ≥4 awakenings
MSI include hormonal changes increasing muscle catabolism, per night. Although the panel could not reach a consensus on
increases in inflammatory processes affecting post-exercise naps or sleep architecture, they did suggest that fewer naps in a
muscle damage, and effects on new bone formation. Sleep can 24-hour period were likely associated with good sleep quality
be optimized by a slightly cool sleeping environment, bed- and more naps in 24 hours with poor sleep quality. 10
ding that maintains a stable thermal microclimate around the
body, not using media devices near bedtime or in the sleeping US military Servicemembers (SMs) consistently report less
environment, minimizing noise, and having regular bed and sleep than the general US population. Data from a large na-
awaking times. Sleep loss mitigation strategies include napping tionally representative samples of Americans indicated that
(<30 to 90 minutes), sleep banking (extended time in bed), and 72% reported ≥seven hours per night. 11,12 Samples of military
judicious use of caffeine or modafinil. SMs indicated that only 42% to 51% reported ≥seven hours of
sleep/night. 13–15 The reasons for inadequate sleep routinely re-
Keywords: sleep; sleep banking; musculoskeletal injury; sleep ported by SMs are multifactorial and can vary significantly de-
deprivation; sleep loss pending on the job, mission, and environment, just to name a
few. In addition, sleep can vary based off whether a SM is in a
training, in garrison, or in a deployed environment and the cir-
cumstances surrounding each of these situations. Considering
Introduction
the added life-stressors deployments may have, it is not surpris-
Adequate, high-quality sleep is an important part of a healthy ing that they can have a negative impact on sleep. In a study
lifestyle. Suboptimal sleep is associated with a host of adverse of deployed Air Force personnel, 74% rated their quality of
health outcomes including higher risk of cardiovascular dis- sleep as significantly worse in the deployed environment with
ease, diabetes, weight gain and obesity systemic inflammation, 40% having a sleep efficiency <85%, 42% with a sleep latency
reductions in neurocognitive functioning, and increased over- >30 minutes, and 14% with total sleep time <4.5 hours. In
16
all mortality risk. The American Academy of Sleep Medi- a study that included SMs from all services, sleep duration
1–6
cine and Sleep Research Society recommend that adults 18–60 was shorter and troubled sleep was more likely among those
*Correspondence to joseph.j.knapik.civ@health.mil
1 MAJ (Ret) Joseph J. Knapik is a research physiologist at the US Army Research Institute of Environmental Medicine and an adjunct professor
at Uniformed Services University (Bethesda, MD) and Bond University (Robina, Australia). Dr John A. Caldwell is a research psychologist for
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the US Army Research Institute of Environmental Medicine and as a principal scientific consultant for Melius Consulting (Perth, Australia) and
Coastal Performance Consulting (Yellow Springs, OH). LTC Bradley M Ritland is the Deputy Chief for the Military Performance Division at the
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US Army Research Institute of Environmental Medicine.
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