Sleep and the Immune System

By Susanne Booth

As we enter into cold and flu season we all become more aware of ways to strengthen our immune system.  One of the easiest and cheapest ways to do this is by paying attention to our sleep.

Sleep is defined as an actively induced, highly organized brain state marked by a reduction in motor activity, lowered response to sensory stimulus, adoption of stereotypic postures (lying down with eyes closed) and easy reversibility.   It takes 90 -110 minutes to go though a sleep cycle.  We all do this 3-5 times per night.  In each 90-110 minute cycle, we go through 4 stages. Rapid Eye Movement (REM) sleep occurs in the first stage of sleep. The deepest sleep is characterized by increased delta brain waves and occurs in stages 3 and 4.  Each cycle is unique; as a person sleeps longer, he or she will spend less time in deeper stage 3 and stage 4 sleep, and longer time in stage two and REM sleep.  Sleep is controlled by a part of the brain called the hypothalamus.  Patients who have a lesion in the anterior hypothalamus suffer from insomnia; those with lesions in the posterior hypothalamus have the issue of excessive sleep. Something else that is regulated by the hypothalamus is a fever.  We all probably know that we sleep more when we have a fever. It is thought that these two may be closely linked.

Did you know that we humans used to sleep a lot more than we do now?  In the first half of the twentieth century most people slept 9 hours per day.  Today, most people average 7.5 hours.  Now that electricity is everywhere and relatively cheap, we are able to stay up much later. Most people have an increased workload.  Family stress and social changes have impacted our time sleeping.

No one really understands why it is we need to sleep. There is research that makes in clear that the lack of sleep impacts our immune system.  Sleep deprivation increases the risk of infections through alterations in immune function. Our sleep changes when we are sick. Rabbits injected with viruses had an increase in non-REM sleep and a decrease in REM sleep.  They spent more time in deeper sleep. These sleep changes were found when animals were injected with bacteria, fungi and parasites.

Mice that were sleep deprived showed signs of immuno-suppression. They had lower antibody titers and were less able to clear their  bodies of viruses.  Chronic sleep loss in rats led to sepsis (a blood infection).  The hormones that were secreted appeared to be the same as those secreted in hypothalamus failure.  A similar pattern was seen in military trainees subjected to sleep loss.  When we are sleep deprived, we have available to us fewer of the proteins necessary to detect infections and tumor cells.  We also have increased levels of proteins that are pro-inflammatory, which can contribute to diseases such as osteoporosis, cardiovascular disease and insulin resistance.  Overall this imbalance can increase morbidity and mortality.

Interestingly, women are better able to tolerate sleep deprivation than men. Women, typically, have better quality of sleep than men.  This may be a genetic variation in order to support women to be up at night breastfeeding and taking care of children.  Healthy women sleep better, can cope with sleep loss better and may have lower cardiovascular risk and greater longevity.

Sleep is an important part of every day.  Now that colds seem to be popping up everywhere, you can help protect yourself by making sure you get enough sleep. If you are sick, get more sleep.  It makes sense to try to sleep more in the winter when there is a shorter day, and save those late nights for the summer when there is more sunlight to energize us.

Susanne Booth is a naturopathic physician, primary care provider, and physical therapist at Sojourns Community Clinic.  For more information, please contact Sojourns at (802)722-4023, 4923 US Route 5, Westminster, VT 05158,, find us on facebook, and visit our blog,

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