Immune function

Are you better equipped to fight a cold if you get a good night of sleep?  That seems to be the case. Cell repair and healing doesn’t happen only when you get injured from a cut or bruise, but there in ongoing repair (even if you didn’t cut yourself) that actually happens every single night and when you are asleep.

During the depth of sleep, growth hormone (GH) is released into our bloodstream and turns on this repair process. Interleukins (IL) and tumor necrosis factor (TNF) are also called cytokines, which are proteins that are released by cells to communicate with other cells. They trigger inflammation in response to infection. They are vital to our defense against harmful bacteria and viruses; in fact TNF goes after cancer cells. These cytokines are released during sleep and are believed to maintain our immune function; their levels drop in the morning shortly after we wake up.

Studies show us that sleep deprivation drops the levels of cytokines. This, then causes immune suppression and susceptibility to viruses including those of the common cold. Since TNF works in fighting cancer cells, one can assume that sleep deprivation increases cancer risk; this idea needs to be confirmed, though. We all have a universal personal experience with sickness or illness. When you get a cold or flu, all you want to do is sleep. Your body aches and you crave to go to bed and drift to sleep. When you get an infection, your body releases the cytokines in response to foreign viruses or bacteria and a battle takes place and we hope that we win and we usually do and that is how we  don’t fall prey to those suckers.

These cytokines influence the brain’s sleep centers and induce sleepiness. In fact, following injection of a bacterial substance (called endotoxin) into human volunteers, researchers were able to induce sleepiness (ref: Hermann DM). While there is good evidence that some infections are somnogenic (sleep inducing), others can also cause sleep disturbance and affect the distribution and quality of sleep and lead to daytime fatigue. Patients who suffer from chronic insomnia often feel fatigued during the day. They have difficulty falling asleep and/or frequent awakenings at night. One study found that there was a shift of interleukin( IL-6) and TNF secretion from nighttime to daytime, which may explain the daytime fatigue and performance decrements associated with insomnia (Vgontzas AN).

If you get a cold or an infection, one of the best medicines you can give your achy body is to get as much sleep as you can. Often, people notice that they feel better as if sleep cleansed their system of the sickness.


Hermann DM, Mullington J, Hinze-Selch D, Schreiber W, Galanos C, Pollmächer T. Endotoxin-induced changes in sleep and sleepiness during the day. Psychoneuroendocrinology. 1998 Jul;23(5):427-37.

Vgontzas AN, Zoumakis M, Papanicolaou DA, Bixler EO, Prolo P, Lin HM, Vela-Bueno A, Kales A, Chrousos GP. Metabolism. 2002 Jul;51(7):887-92. Chronic insomnia is associated with a shift of interleukin-6 and tumor necrosis factor secretion from nighttime to daytime.