Conventional wisdom is that when a person contracts an bacterial or viral infection, they should stay in bed (and drink chicken soup!). Sleep is commonly regarded as a way to rest the body so that it can marshal resources necessary to fight infection and recover. Sleep, along with waking rest is seen as a way to combat the fatigue associated with the illness. But sleep is much more than a state of rest for energy restoration. We now know some of the reasons that sufficient sleep is one element in preventing infection and mitigating the severity and duration of effects once infection is contracted. Research over the last few decades has enhanced our understanding of how processes that occur during sleep are central to the regulation of multiple physiological systems, including the immune system. (Madje & Kruger 2005). Fever is a critical immune response to infection, and during sleep, immune signaling molecules (e.g Interleukin 1- a cytokine) regulate the fever response. One mechanism thought to be instrumental in this process is through modifications in the pattern of REM and Non-REM sleep cycles (Imeri & Opp, 2009).
Adolescents have been shown to be sleeping less than they need, and a recent study of high school students in Rhode Island has established a link with common illnesses. While previous research linking sleep and illness has been laboratory based, this study is the first to follow adolescents over a long period in their natural setting. Orzech, Acebo, Seifer, Barker, & Carskadon (2013) report in a recent issue of the Journal of Sleep Research results of their prospective field-based study of sleep duration and incidence of illness. Using actigraphy to measure sleep objectively, they divided adolescents into two groups—longer sleepers who slept an average of about 7 ½ hours during weekdays—and shorter sleepers whose sleep was around 6 ½ hours. Over a period of five months, weekly interviews were conducted that asked about numbers of bouts of illness and durations. Accidental injuries such as bruises, sprains, or cuts and symptoms from chronic illnesses such as asthma were categorized separately from illnesses caused by infection, including colds, flu, and gastroenteritis. Absences from school due to illness were also recorded. Longer sleepers were found to have fewer bouts of illness, and shorter durations of illness. Further, a trend was found that sleep for all adolescents was shorter in the 6 day interval before the onset of an illness. There was a tendency for shorter sleepers to be absent when they were ill. The study authors provided two case summaries that illustrate vividly sleep habits of typical adolescent participants. One studentwho slept only an average of 6 hours a night reported that he tries to catch up on sleep during school breaks and calling in sick from his weekend job to get extra sleep. He also reported frequent instances of excessive daytime sleepiness. Another student slept an average of 5 ½ a night on school nights and 7 hrs- 19 min on weekends. He said he often begins work on school projects or his self-employed job repairing computers around 5:00 or 6:00 PM and works through the night until 4:00 or 5:00 AM. Then he naps often at school to catch up on lost sleep.
In previous posts, I have summarized research showing that insufficient sleep is related to poor attention and alertness necessary for learning new material, and to poor sleep-dependent memory consolidation. The research on sleep and illness adds another dimension to the link between poor sleep and academic underachievement. No student’s learning is optimal when they are sick, and when illness results in school absence, fewer opportunities for instruction are afforded, presenting further challenges.
Imeri, L. & Opp, M.R. (2009). How (and why) the immune system makes us sleep. Nature Reviews Neuroscience, 10, 199-210. doi: 10.1038/nrn2576
Madje, J.A. & Krueger, J.M. (2005). Links between the innate immune system and sleep. Journal of Allergy and Clinical Immunology, 116, 1188-1198. doi: 10.1016/j.jaci.2005.08.005
Orzech, K.M., Acebo, C., Seifer, R., Barker, D., & Carskadon, M.A. (2013). Sleep patterns are associated with common illness in adolescents. Journal of Sleep Research, published online October 13, 2013. doi: 10.111/jsr.12096