COMDTINST 3500.2
(b) Poor Sleep Quality. While the continuous 8-hour period of sleep is important, if the
quality of sleep is poor, the restorative value of that sleep is reduced. In some respects,
the quality of the sleep is as important, if not more important, than how long one sleeps.
Sleep environments that are hot, noisy, bright, or that have uncomfortable bedding
compromise the quality and restorative value the sleep.
(c) Fragmented Sleep. Sleep is fragmented when the physiological ideal 8-hour sleep
period is split into two or more episodes. For example, a person standing the mid-watch
typically has one sleep episode before watch and a second sleep episode after watch. In
order for sleep to be restorative the brain needs to progress through various sleep stages
that restore different physical and mental functions throughout the 8-hour sleep period.
When sleep is fragmented, sleep stages are disrupted and energy restoration is
compromised.
(d) Main Sleep During the Day. Human physiology is programmed for sleep during night
hours (2200 to 0600) and be awake during day hours (0600 to 2200). During these
times, specific biochemical activities occur that promote sleep and alertness. Sleep
during daylight hours disrupts these biochemical cycles with predictable consequences:
loss of attention and alertness, sleepiness, and fluctuations in mood. Adapting to night
work requires adjusting the release of biochemicals, but this adjustment can take days,
and might not occur at all, depending on how much control members have over their
work/home environment.
(e) Changing Work/Rest Schedule. Switching from day to night work produces
physiological disruptions very similar to those experienced in `jetlag'. Standing a watch
schedule that rotates from day to night is like crossing multiple time zones every time
the schedule rotates. As in jetlag, this `shiftlag' produces consistent decrements in
alertness, performance, and physical and mental functions that can take upwards of one
week to recover from.
(f) Long Work Days. Human performance begins to decrease approximately 12 hours after
one arises from sleep. After approximately 14 hours of wakefulness, individuals
perform at levels compared to someone with a blood alcohol concentration (BAC) of
.05. After approximately 26 hours of wakefulness, individuals perform at levels
compared to someone with a BAC of .10. These performance levels will vary as a
function of type of task, environmental conditions and history of the individual.
(g) No Opportunities to Make Up Sleep. If a sleep period is less than the physiologically
ideal 8 hours per, the difference between the actual, say 6 hours, and the ideal, 8 hours,
is called a "sleep debt" and must be must be made up at a later time. The body naturally
extends normal sleep periods to make up the lost sleep. For most people sleep on
weekends is extended for this purpose, to make up for any lost sleep during the
workweek. If sleep debt is not paid back, it continues to accumulate until the individual
extends their sleep beyond the 8 hour basic need and begins to pay back their
accumulated sleep debt. Because human physiology requires that sleep debt be paid
back in full, unpaid sleep debt will result in chronic sleep deprivation, and produce
decrements in performance, erratic moods, unpredictable behavior and poor health.
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