Scientists have determined how sleep affects immunity
The amount of sleep determines the level of growth hormone and prolactin in the human body. They affect the quality of the immune response, scientists from Germany have found out.
Physical and psychological health of a person largely depends on the sleep schedule, which in the modern world manages to keep only 15% of people. Studies have shown, for example, that insufficient sleep increases the risk of type 2 diabetes, and a sharp awakening on the alarm clock provokes a spike in blood pressure.
Specialists from the Eberhard and Karl University of Tübingen, Ludwig-Maximilian University of Munich and the University of Lübeck (all in Germany), found that sleep, among other things, stimulates the human immune system. The results of the experiment, which involved seven men and seven women, were published in the journal Brain, Behavior, and Immunity.
The study participants were monitored for two 24-hour sessions. Scientists measured the concentration of T-lymphocytes, cells that play an important role in the immune system, several times during each period. During one of the sessions, experimental participants were allowed to sleep for eight hours at night (blood was drawn by a catheter on the forearm without disturbing sleep), and during the other they could lie in bed, watch TV, listen to music, and talk to the experimenter to reduce the effects of melatonin, but not fall asleep.
The people who participated in the study were between 18 and 30 years old. They were all healthy, had a body mass index between 20 and 25 (i.e. normal), and had not taken any intercontinental flights, consumed no alcohol or psychoactive substances, or donated blood for six weeks before the experiment. Between sessions was a minimum of four weeks, the conditions of the experiment were "equalized" so that some of the participants were not exposed to factors that did not affect the rest: for example, women came to the laboratory in the same phase of the menstrual cycle.
It turned out that blood test results were largely dependent on the amount of sleep. People who slept at night had an improved ability of T-cells to migrate to the lymph nodes. This is where the immune defense is "trained" when an antigen - a substance that is regarded as foreign - enters the body (for example, as a result of vaccination).
The scientists named growth hormone and prolactin as the decisive factors that caused this behavior of T-cells: their level was higher in the study participants who slept at night. These substances can then be used to stimulate the body's immune response after vaccination. This is especially relevant for the elderly, for whom vaccines are often less effective, the authors of the study explained.