Why do we feel sleepy when we’re sick? Study finds out

Have you ever wondered why do you feel the need to sleep more when you’ve fallen sick? Researchers from University of Pennsylvania took it to themselves to find out. Their study of over 12,000 lines of fruit flies, found the single gene, called nemuri that increases the need for sleep.

Our body is protected from germs and their inherent antimicrobial activity because of the nemuri protein and it is secreted by cells in the brain to drive prolonged, deep sleep after an infection. "While it's a common notion that sleep and healing are tightly related, our study directly links sleep to the immune system and provides a potential explanation for how sleep increases during sickness," said Amita Sehgal, Professor at the varsity.

In absence of the nemuri gene, flies were more easily aroused during daily sleep, and their acute need for an increase in sleep -- induced by sleep deprivation or infection -- was reduced. Sleep deprivation stimulated nemuri to be expressed in a small set of fly neurons nestled close to a known sleep-promoting structure in the brain.

In conclusion, over expression of nemuri saw an increase in sleep in bacteria-infected flies and led to their increased survival compared to non-infected control flies. The findings also said nemuri kill microbes, most likely in the peripheral parts of the fruit fly body and increases sleep through its action in the brain.

Moreover, the researchers, in the study published in the journal Science, noted that an immune cell molecule -- interleukin-1 (IL-1) -- is implicated in human sleep. IL-1 accumulates after prolonged wakefulness and appears to promote sleep, suggesting that nemuri is a working link between immune function and sleep.