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physically active participants (athletes) concluded that longer Modafinil
napping opportunities (i.e., 90 minutes) resulted in better im- Modafinil is a wakefulness promoting drug approved by the
provements in physical and cognitive performance and lower Food and Drug Administration for excessive daytime sleepi-
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fatigue. A practical suggestion is that when optimal perfor- ness associated with narcolepsy, shift work sleep disorder, and
mance is required immediately after napping, shorter naps obstructive sleep apnea (the latter when used as an adjunct to
(<30 minutes) should be taken in an effort to reduce sleep continuous positive airway pressure [CPAP]). It is a Sched-
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inertia upon awakening. However, if time can be allowed to ule IV prescription drug. A number of studies have indicated
recover from the effects of sleep inertia before optimal perfor- that modafinil reduces sleepiness and improves mood and
mance is required, longer naps (90 minutes) can be taken. 88 cognition in sleep-deprived individuals. 103–110 For example,
modafinil at a dose of 200–400mg was shown to maintain
Caffeine objective cognitive performance on vigilance and alertness
Caffeine is a widely consumed psychoactive stimulant ingested tasks in a manner similar to 600mg of caffeine. In another
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in various beverages including coffees, teas, sodas, and energy study of helicopter pilots, three 200mg doses of modafinil
drinks. About 87% of SMs consume caffeinated products with administered 16, 20, and 24 hours without sleep resulted
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an average intake of average intake of 243mg/day. Compre- in higher flight simulator performance in four of six flight
hensive reviews have concluded that consumption of ~400mg/ maneuvers. Some cognitive effects may be dependent on
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day is generally safe, enhances certain aspects of mental, phys- genotype. Modafinil appears to act by inhibiting dopamine
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ical, and occupational performance, and may confer other transporters and thus increasing dopamine content, while
health benefits. 90–92 Among healthy adults, moderate coffee also elevating norepinephrine and serotonin in the prefron-
consumption has been reported to be associated with reduced tal cortex and hypothalamus. 102,112 Some minor side-effects
risk of certain health conditions including chronic liver disease, have been reported in an estimated 10% of users including
gout, Parkinson’s disease, Alzheimer’s disease, type 2 diabetes, headaches, nausea, reduced appetite, dizziness, diarrhea, and
certain types of cancers, all-cause mortality, and cause- specific rhinitis. 102,106,108 Modafinil appears to have a low potential for
mortality. 90,93,94 Caffeine appears to enhance cognition and addiction at therapeutic dosages, although there are case re-
physical performance through at least two mechanisms. Ade- ports of abuse mostly in individuals suffering from pre-intake
nosine promotes sleep, and caffeine binds to adenosine recep- psychiatric disorders and involving large dosages. 113
tors reducing adenosine’s central nervous effects by enhancing
the neurotransmitters dopamine and noradrenalin. A second Summary
mechanism involves augmentation of nitric oxide that im-
proves blood flow and neuromuscular function. 95–98 The limited literature on the association between sleep and
MSI in military personnel suggests that both lower sleep qual-
Studies of military personnel in operational training scenar- ity and quantity is associated with a higher incidence of MSI.
ios involving almost total sleep deprivation have shown that However, most studies on this topic have limitations including
a single dose of caffeine (100, 200 or 300mg) improved vig- the use of convenience samples (rather than random samples),
ilance, reaction time, attention mood, and lowered sleepiness use self-reports of sleep quality/duration (rather than more ob-
and sighting time on a marksmanship task when compared jective measures), and involve self-reports of injuries (rather
to a placebo. 25,30 When multiple dosages (50–200mg) were than clinically diagnosed injuries). It is possible that poor sleep
provided during military operational scenarios involving sleep quantity or duration may make active individuals more sus-
loss, it was found that vigilance, alertness, and marksmanship ceptible to MSI because of 1) sleep-related hormonal changes
accuracy were enhanced compared to a placebo. 31,99 A system- that increase muscle catabolism, 2) increases in inflammatory
atic review of 25 studies concluded that during sleep depri- processes and post-exercise muscle damage, and 3) effects on
vation caffeine improves attention, vigilance, reaction time, new bone formation. Sleep can potentially be optimized by an
problem solving, reasoning. It has been recommended that environment with 1) slightly cool air temperatures, 2) bedding
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100mg of caffeine (about one cup of coffee) be taken every that maintains a stable thermal microclimate around the body,
3–4 hours, not to exceed 600mg/day, to maintain cognitive 3) avoidance of media devices near bedtime or in the sleep-
functioning during periods of sleep deprivation. Besides caf- ing environment, 4) minimizing light and noise, and 5) hav-
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feine’s effects on cognitive functioning, there is ample evidence ing regular bed and awaking times; military personnel should
that caffeine can improve aspects of physical performance in- consider this whenever the mission permits. When it is not
cluding cardiorespiratory endurance, muscular strength, and possible to optimize sleep and the environment in which sleep
anaerobic endurance. 95 is occurring, mitigation strategies include napping (<30 to 90
minutes), sleep banking (spending extra time in bed in order to
2-B-Alert get more sleep), consumption of caffeinated substances, and/
2-B Alert is an educational and informational software tool or use of modafinil. Future research is needed to determine if
that predicts the alertness of an average individual as a func- optimizing sleep environments or any mitigation strategies has
tion of their sleep/wake schedule, caffeine consumption, and any subsequent impact on injury risk.
time of day. It is available at https://2b-alert-web.bhsai.org
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/2b-alert-web/login.xhtml and requires a free subscription. Disclaimer
Users manually enter a sleep/wake/peak alertness schedule, as The views expressed in this presentation are those of the au-
well as caffeine consumption and timing, and the system dis- thor(s) and do not necessarily reflect the official policy of the
plays predictions for three different statistics of alertness. If the Department of Defense, Department of the Army, US Army
user provides the desired period of peak alertness, the system Medical Department, or the US Government. The use of trade-
will output the estimated optimal caffeine schedule. First time mark names do not imply endorsement by the US Army but
users should consult the “Help” button on the website that is intended only to assist in the identification of a specific
provides instruction on how to use the software. product.

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