It is surprising how beneficial short 30 minute naps are after sleep deprivation. From Medscape:
Simply taking a couple of naps may counteract the impact of a sleep-restricted night on stress and immune markers, a finding that could potentially benefit night and shift workers or other chronically sleep-deprived populations, the results of a French study indicate.
Brice Faraut, PhD, from the Université Paris Descartes-Sorbonne Paris Cité, France, and colleagues found that, after a night with only 2 hours of sleep, taking two naps of just 30 minutes each appeared to normalize levels of cytokines and catecholamines.
"Napping as a countermeasure to sleep restriction could, in addition to benefits on alertness, improve neuroendocrine stress and immune recovery, with a potential prophylactic long-term effect on cardiovascular health," the researchers write.
They conducted their crossover, randomized study in which 11 healthy men aged between 25 and 32 years underwent two sessions of laboratory sleep testing in which their sleep–wake status, light environment, and caloric intake were strictly controlled.
In a "sleep-restriction" session, the participants slept for just 2 hours for one night after a baseline night of 8 hours of sleep, followed by a recovery night of sleeping. In the "sleep-restriction/nap" session, they repeated the protocol, but with two 30-minute naps after the sleep-restricted night. Salivary samples were taken every 2 hours and analyzed for interleukin (IL)-6 levels, an inflammatory cytokine known to have diurnal variations in concentration. In addition, urine samples were taken every 3 hours to measure levels of epinephrine, norepinephrine, and dopamine.
In the sleep-restricted session, there was a significant 2.5-fold increase in norepinephrine levels in the afternoon compared with the control day (P = .003). However, those differences were not seen when participants were able to take two 30-minute naps. No significant differences were seen either for epinephrine or dopamine, the researchers report.
After a sleep-restricted night, IL-6 levels were significantly lower at 10:00 am and 7:00 pm than levels measured at the same times after the control night's sleep (P = .01 and P = .05, respectively). Again, those differences were not observed when participants were able to take the two 30-minute naps.
Interestingly, daytime napping was associated with a significantly reduced amount of slow-wave sleep during the recovery night compared with sleep restriction alone (P = .01) and a trend toward decreased total sleep time."Our data suggest that napping has stress-releasing and immune effects," the researchers conclude.