Two 30-minute naps relieved stress and bolstered the immune system of men who slept only 2 hours the night before, according to results of a small study published in the Journal of Clinical Endocrinology & Metabolism.
“Our data suggest a 30-minute nap can reverse the hormonal impact of a night of poor sleep,” Brice Faraut, PhD, study researcher from the Université Paris Descartes-Sorbonne Paris Cité in Paris, said in a press release. “This is the first study that found napping could restore biomarkers of neuroendocrine and immune health to normal levels.”
In the randomized, crossover study, 11 healthy, nonsmoking young men (age range, 25 to 32 years, BMI, 19 to 25) were strictly controlled in a laboratory environment in terms of sleep-wake status, light environment and caloric intake, and were monitored continuously via polysomnography.
Dr. Faraut and colleagues examined neuroendocrine and immune biomarkers of a night of sleep restricted to 2 hours, which was followed by a day without naps or with 30-minute morning and afternoon naps. Patients then underwent an ad libitum recovery night of sleep following the sleep-restricted night from 20:00 to when they woke up.
Main study outcome measures were salivary interleukin-6 (IL-6) and urinary catecholamines, which were evaluated throughout the daytime study periods.
The afternoon (16:00 to 19:00) after the sleep-restricted night, researchers found a 2.5-fold increase in norepinephrine levels compared with the same period during the control day (P=.03). These changes, however, were not observed after a 30-minute nap in the morning and afternoon (P=.88).
Similarly, differences in interleukin-6 levels were comparable between those who napped after sleep deprivation and the control group (P=.51).
In addition, levels of afternoon epinephrine and dopamine were increased during the recovery day for patients who did not nap, which was not the case for those who did. There was also an association between the recovery night of those who napped and a reduced amount of slow-wave sleep compared with those who did not nap.
“Napping may offer a way to counter the damaging effects of sleep restriction by helping the immune and neuroendocrine systems to recover,” Dr. Faraut said. “The findings support the development of practical strategies for addressing chronically sleep-deprived populations, such as night and shift workers.”