People, particularly in survival situations, tend to shortchange their need for sleep. You need all the mental power and alertness you can muster. Even if you aren't wiling to buy that you need to value sleep more than food I think we need to, at the very least, get sleep on the same list as water, food and shelter.

http://blogs.hbr.org/schwartz/2011/03/sleep-is-more-important-than-f.html

IMHO, no disaster or emergency plan is complete without a sleep/awake plan. Moving it sleep up the list also can effect what gear you include. In my experience a $4 sleep mask and $1 earplugs can make a getting some sleep much easier.