Sleep fights infection

Is sleep the ultimate cure? When we get sick we all feel like lying in bed all day and not doing anything. But can sleep really help us recover from disease? Yes! According to recent research from University of Pennsylvania, we should sleep more when we are ill, because sleep can strengthen our immunity and help us fight infections.

“When you get sick, you should sleep as much as you can”, asserts Center for Sleep and Circadian Neurobiology research associate Julie A. Williams, PhD, and “we now have the data that supports this idea”. In two related papers supported by National Science Foundation and published in the journal Sleep, the Penn team demonstrated that fruit flies that slept more after infection had a higher survival rate. The reason Williams along with post-doctoral fellow Dr. Tzu-Hsing Kuo used the fruit fly as a model to conduct their study is that genetic factors examined in the fruit fly are well conserved in mammals. Thus, results from simple experiments on fruit flies yield reliable conclusions that are relatable to humans.

In their first study, Williams and the rest of her team showed that when fruit flies were infected with one of the two types of common bacteria – either Serratia marcescens or Pseudomonas aeruginosa – the flies that slept more were the ones more likely to survive. They used two groups of flies – sleep-deprived and non-sleep-deprived – and noticed that both groups tended to sleep more after infection.

The Penn team was shocked to learn that among the flies that slept after infection, the pre-experimentally sleep-deprived fruit flies were more likely to survive infection than the non-sleep-deprived individuals. Whether flies were deprived of sleep prior to or post infection did not matter, as long as flies could sleep enough afterwards they would recover.

"We deprived flies of sleep after infection with the idea that if we blocked this sleep, things would get worse in terms of survival. Instead they got better, but not until after they had experienced more sleep," says Williams. She associated her finding with the fact that pre-experimentally sleep-deprived flies are likely to sleep for longer after infection than the undisturbed flies. The duration of post-infection sleep determines the flies’ recovery rate from infection. 

Such findings of the team are innovative because no previous research has been able to connect the quantity of sleep and disease recovery. “Many studies have used sleep deprivation as a means to understand how sleep contributes to recovery, if it does at all, but there is surprisingly little experimental evidence that supports the notion that more sleep helps us to recover,” explains Williams.

Researchers did not stop there, but went on to further explore the relationship between sleep deprivation and infection fighting. Relish – an NFkB transcription factor – is helpful in combatting infections and is also known to be activated in sleep-deprived fruit flies: individuals, in which the Relish gene is knocked out, do not have the acute sleep response and so succumb to infection. However, when the Penn team deprived of sleep the knockout group of flies prior to infection, the flies slept more after infection and survived better. When examining fruit flies lacking two types of NFkB transcription factors –– researchers found that sleep-deprived and undisturbed groups succumbed to infection at equal rates. Without Relish and Dif sleep deprived flies did not experience the acute sleep response, and so the effect of sleep on their recovery and survival was no longer observed.

“Taken together, all of these data support the idea that post-infection sleep helps to improve survival," notes Williams.

Building on the results of their Relish experiments, the Penn team decided to use a genetic approach to change the sleep patterns in flies. In their second study researchers showed that fruit flies, genetically induced to sleep for longer periods of time prior to infection, survive and recover better than the fruit flies that slept normally. “Increased sleep somehow helps to facilitate the immune response by increasing resistance to infection and survival after infection,” says Williams.

Using the drug RU486 the scientists were able to control the sleeping patterns of the fruit fly: they induced the ion channels’ expression to alter neuronal activity in the mushroom body of the fly brain. Thus, they created flies that for up to two days before infection slept for longer durations than the control group, and these mutants were able to recover faster than the control group.

Hence, in just two studies the Penn team was able to provide valuable insights into the process of increased recovery with sleep, which is commonly observed and believed in, but which previously had no scientific basis. "Investigators have been working on questions about sleep and immunity for more than 40 years, but by narrowing down the questions in the fly we're now in a good position to identify potentially novel genes and mechanisms that may be involved in this process that are difficult to see in higher animals,” comments Williams.

Perhaps, with this knowledge in hand we will stop feeling guilty about missing work and deadlines due to sickness. Sleep is useful for recovery. While William and her team continue delving into the mechanics of the process, we can learn from her research and sleep more when overcome by disease.

REFERENCES

Chan A. L. (2014, April 24). Why It's Good To Sleep A Lot When You're Sick. Huffington Post. Retrieved from http://www.huffingtonpost.com/2014/04/24/sleep-sick_n_5193328.html

How You Can Fight Disease with Sleep. (2014, April 29). The Alternative Daily. Retrieved from http://www.thealternativedaily.com/can-fight-disease-sleep/

Nayan K. (2014, April 23). Sleep And Immune Function in Fruit Flies Are Linked. Counsel Heal. Retrieved from http://www.counselheal.com/articles/9461/20140423/sleep-immune-function-fruit-flies-linked.htm

Research shows sleep can boost immune system and fight infection. (2014, April 30). Carribean 360. Retrieved from http://www.caribbean360.com/news/research-shows-sleep-can-boost-immune-system-and-fight-infection

Sleeping Away Infection: Penn Researchers Find Link between Sleep and Immune Function in Fruitflies. (2014, April 22).  Penn Medicine. Retrieved from http://www.uphs.upenn.edu/news/News_Releases/2014/04/williams/

Surprising Results from Research About Sleep and Illness. (2014, April 22). Sleep Better. Retrieved from http://sleepbetter.org/surprising-results-sleep-and-illness/

 

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