It is officially flu season and I hope you got your flu shot. Even if this year’s flu shot isn’t perfect, we need any help we can get to avoid or minimize the flu and its symptoms. While we often think of the flu as an annoying affliction that will make us miserable or cost us a week off from work, we may not realize it has a history that is truly chilling. Influenza is caused by an easily transmitted viral agent that results in about a week of very unpleasant symptoms such as high fever, cough, sore throat, runny nose, headache and aching muscles. It can lead to death, which usually occurs in the elderly, young children and people with compromised systems due to other serious illness. There have been influenza pandemics, however, that have rivaled the worst pandemics in human history. One of the worst was the 1918 “Spanish Flu” outbreak that killed more people than the First World War, that was then in progress, and that may have exceeded the death toll of the Great Mortality (Black Death). What made that strain of the flu so deadly was that it attacked young and otherwise healthy adults and was especially virulent, resulting in a high death rate among people who would typically have survived an ordinary flu. There was some controversy recently when the virus that was responsible for the Spanish flu was reconstructed. Some were concerned that if the Spanish flu virus were brought back to life, then information about it could be used by terrorists to create a dangerous weapon.
The 1918 epidemic was nearly forgotten in history for reasons that are unclear. Perhaps it was that there were other momentous events occurring in the world at the time, such as the collapse of the empires involved in the old 19th century European order, or perhaps it was because people were so focused on the numerous battle field events of the time. Nevertheless, the stories of people who were experiencing the epidemic, including soldiers, are sobering. It has been debated to what extent, if any, the First World War impacted the outbreak. Would it have happened anyway or was it greatly magnified by massive global troup movements as well as by the people’s immune systems, which had been weakened by the stress, poor eating, and loss of good sleep that are part of the privations of war. The answer may never be known, but certainly susceptibility to infectious illness is enhanced by such factors as poor eating and sleep loss.
Sleep is an important component to a healthy immune system. Infections and inflammation often result in sleepiness. This is caused by the release of immune factors known as cytokines, including interleukin-1 and interferon. It seems that when fighting an infection the body wants to conserve energy for that battle and encouraging sleep and rest helps in this regard. While sleep is helpful in fighting infectious illness, sleep deprivation has effects on the immune system and usually impairs its functioning. For example, sleep deprivation can impair the immediate immune response to the flu vaccination. Sleep deprived individuals express less than half the influenza anitbodies that are seen in controls. Whether or not this has long lasting effects on the effecitveness of the vaccine is not know at this time (Krueger & Majde, 2011). When watching TV, I often wonder about the wisdom of the commercials that recommend taking cold and flu remedies that are supposed to let us keep working. These over the counter medicines work against what our ailing bodies want us to do - stay home, sleep and rest. Instead, they allow us to avoid taking time off to recover from illness, and bring us into proximity with others whom we may infect. While it is true that sometimes we simply can’t take time off, if we possibly can stay home when sick, this benefits not only ourselves, but also those around us.
Infection activates the immune system and this has systemic effects on the body and thus on sleep. The immune response not only causes increased sleepiness, it also alters the nature of sleep itself. As the immune system fights infection, the amount of time spent in REM sleep is decreased while deep sleep is increased. This makes sense as it is during deep sleep that many reparative bodily processes occur. Enhanced deep sleep appears to occur as a result of processes activated by the release of cytokines. It has been observed in animals that when challenged by an infection, the animals that have a strong increase in deep sleep have a significantly better chance of surviving the infection than those that fail to show this response.
Sleep deprivation alters immune function and appears to generally reduce resistance to infection. People who sleep less have decreased resistance to viral activity. Interestingly, a small decrease in sleep may actually activate the immune system and thus provide some advantage for fighting illness, but prolonged sleep loss has terrible effects on the immune system. In an earlier blog I discussed how long it might take a human to die from total sleep loss. While there are no records of a human dying directly from sleep loss (as opposed to being killed in a car accident after falling asleep at the wheel or because they have a rare genetic illness known as Fatal Familial Insomnia), it is theoretically possible and can be demonstrated in animals. The cause of death in prolonged near total sleep deprivation in rats is sepsis. In a rat this requires two to three weeks nearly without sleep. Dying from sleep loss would, of course, take much longer in a human.
As the flu season is upon us, it is a good idea to get the flu vaccination. Getting good sleep and being rested prior to the injection will help the immune response to the vaccine be most effective and protective. Getting good sleep is not a guarantee that you won’t get the flu but it will help maximize your chances of being as resistant as possible. This is important as you will inevitably encounter other people who have already contracted the virus and may be spreading it into the environment. If you do come down with flu, follow grandmother’s advice and get a lot of sleep. It really will help your body fight the illness and speed recovery. Don’t take the “keep going no matter how sick you are” over-the-counter preparations. The flu is more serious than a cold and paying attention to that sense of really needing to sleep will be far more helpful to you in the long run. Remember that when fighting infection, hot soup and TLC will help you feel better, but the best available scientific evidence supports the vital role of good sleep!
American Academy of Sleep Medicine (2014). International Classification of Sleep Disorders 3rd Edition. Darien, IL: American Academy of Sleep Medicine.
Krueger, J. M. & Majde, J. A.(2011). Sleep and host defense. In Kryger, M. H., Roth, T., & Dement, W. C. (Eds.) (2011). Principles and practice of sleep medicine. St. Louis: Elsevier Saunders.
Lee-Chiong, Jr., T. (2008). Sleep Medicine Essentials and Review. New York: Oxford University Press.