The study Napping Reverses The Salivary Interleukin-6 And Urinary Norepinephrine Changes Induced By Sleep Restriction examined the relationship between hormones and sleep in men. Eleven men between the ages of 25 and 32 underwent two sessions of laboratory sleep testing. Meals and lighting were strictly controlled and the researchers also analyzed the participants urine and saliva to determine how restricted sleep and napping altered hormone levels.
Each three-day session began with a full eight hours for sleep and ended with a recovery night of unlimited sleep. In one session the men were limited to two hours of sleep for one night. The second session allowed the men to take two 30-minute naps the day after their sleep had been restricted for two hours.
Heres What The Researchers Learned
- After a night of limited sleep, the men had a 2.5-fold increase in levels of norepinephrine, a hormone and neurotransmitter involved in the bodys fight-or-flight response to stress. Norepinephrine increases the bodys heart rate, blood pressure and blood sugar. Researchers found no change in norepinephrine levels when the men had napped following a night of limited sleep.
- Lack of sleep also affected the levels of interleukin-6, a protein with antiviral properties, found in the subjects saliva. The levels dropped after a night of restricted sleep, but remained normal when the subjects were allowed to nap. The changes suggest naps can be beneficial for the immune system.
Our data suggests a 30-minute nap can reverse the hormonal impact of a night of poor sleep, said JCEM study authors Brice Faraut, PhD, of the Universit Paris Descartes-Sorbonne Paris Cit in Paris, France. This is the first study that found napping could restore biomarkers of neuroendocrine and immune health to normal levels. Napping may offer a way to counter the damaging effects of sleep restriction by helping the immune and neuroendocrine systems to recover. The findings support the development of practical strategies for addressing chronically sleep-deprived populations, such as night and shift workers.