Sleep deprivation is more common in military personnel due to missions and military operations, and they are scheduled to be deprived of sleep at special times at night posts, respectively. However, sleep deprivation has effects negative and irreversible. Therefore, the purpose of the present study was to investigate the functional response, immune system and hormonal levels of the military to short-term sleep deprivation at different times of the night.

The present study began with the purposeful and voluntary selection of 40 healthy military personnel, they were randomly divided into 4 groups (Group 1: Deprivation from 12am to 2am; Group 2: Deprivation from 2am to 4am, Group 3: Deprivation from 4am to 6am and Group 4: control group). Each group was evaluated in two stages before and after sleep deprivation.

There was a significant difference in pre and post-test sleep deprivation hours 12am to 2am static and dynamic balance, auditory and visual reaction time. Also, in deprivation hours 2am to 4am significantly changed the auditory and visual reaction time and cortisol. In addition, were increased cortisol and melatonin at time 4am to 6am (p<0.05).

The negative effects of sleep deprivation appear to occur at different dimensions and with different times, but only 12 to 2 deprivation have a deleterious effect on balance and reaction time and 2 to 4 deprivation on reaction time and cortisol.