It’s not just beauty sleep

Why sleep is essential for a healthy immune system.

by Dr. Sarah Nyrose BSc ND

Sleep deserves more recognition for the important role it plays in our immune system.

Growing up, whenever I started to feel a tickle in my throat, or the onset of a runny nose, my parent’s predictable response was: “you must not be getting enough sleep.” Sleep was their sage advice for any ailment, and as a teenager, who preferred to stay up watching television, their insistence on going to bed early was received begrudgingly with scepticism.

After all, how much does sleep really impact our immune system?

Well, twenty years later, after having read numerous books and academic papers on sleep, I have to say: my parents were right.

Sleeps impact on our immune system, while often overlooked and underplayed, is profound. Our immune system relies on adequate sleep to efficiently operate and to deploy all manner of defences against invading pathogens. Sleep deprivation results in a diminished immune response: less T-cells (immune soldiers) are deployed, immune signalling is weakened, inflammation is heightened, and the body has a decreased ability to trap and contain viruses.1

There is an intimate relationship between sleep and the immune system. When we fall ill, the immune system actively stimulates sleep, reinforcing the innate and adaptive immune function that will battle against the contracted pathogen. 2 Feeling tired while you’re ill is not just a result of fighting off a bug, your body is trying to make you sleep.

In one study conducted at the University of California, researchers thoroughly investigated the question: how does sleep deprivation affect our immune response?

The sleep duration and continuity of 150 men and women was observed over a one-week period. Following, the participants were given a good dose of the cold virus (rhinovirus) and were then monitored intensely over five days. Their snot was collected, their blood was taken and their vitals continually checked – all of these measurements were used to determine if someone objectively caught the cold.

Retrospectively, the men and women were separated into different groups based on how much sleep they got on average, per night, the week prior to being infected: less than 5 hours, between 5-6 hours, between 6-7 hours and more than 7 hours.1

There was a clear, linear relationship between the amount of sleep and the percentage of participants who fell ill. In the group who received less than 5 hours of sleep, approximately 45% caught the cold, compared to only 18% in the group who slept longer than 7 hours.1

Similar results have been replicated in other studies. For instance, one study found that in a sample of nearly 57,000 women, those who reported less than 6 hours of sleep per night were at a significantly higher risk of developing pneumonia compared to those sleeping 8 hours per night.3

The importance of sleep does not just extend to viral infections, the common cold or flu. In fact, some of the most profound research on the implications of sleep on are immune system have focused on the natural killer cell.

In the group who received less than 5 hours of sleep, approximately 45% caught the cold, compared to only 18% in the group who slept longer than 7 hours.

Natural killer cells are the badass, powerful assassins of your immune system. They are tasked with identifying the bad and the dangerous, and swiftly eliminating them. This includes cancer cells.

One study investigated the impact of modest sleep deprivation on natural killer cell function among young, healthy men. One night of four hours of sleep (between 3am and 7am) reduced natural killer cell numbers to below half of what they started with. Furthermore, the activity or effectiveness of the remaining cells was significantly reduced.4

This is profound, and shocking that one night of sleep-deprivation can cause such a shift in our immune system. It’s not hard to imagine the detrimental effect caused by weeks, months and years of poor sleep. More evidence is supporting that poor sleep increases the risk of cancer development and progression.

Yet we live in a culture that reveres “hustling” and equates being busy with being important and successful. The percentage of adults who sleep less than 6 hours per night is now greater than any other time in history. 5 We sacrifice sleep for our full schedules, one more Netflix episode, or for time-alone.

During cold and flu season, it’s imperative that we prioritize sleep. Rather than looking for the miracle immune booster, sleep is perhaps our best defence. Getting enough of it is not flashy, takes dedication, and requires making adjustments to your schedule.

But if you’re feeling run-down, and can sense a cold brewing, you likely aren’t getting enough sleep. Just like my parents said.

 Stay tuned for some sleep-supporting teas.

  1. Prather, A. A., Janicki-Deverts, D., Hall, M. H., & Cohen, S. (2015). Behaviorally assessed sleep and susceptibility to the common cold. Sleep, 38(9), 1353-1359.

  2. Davis, C. J., Dunbrasky, D., Oonk, M., Taishi, P., Opp, M. R., & Krueger, J. M. (2015). The neuron-specific interleukin-1 receptor accessory protein is required for homeostatic sleep and sleep responses to influenza viral challenge in mice. Brain, behavior, and immunity, 47, 35-43.

  3. Patel SR, Malhotra A, Gao X, Hu FB, Neuman MI, Fawzi WW. A prospective study of sleep duration and pneumonia risk in women. Sleep 2012;35:97–101.

  4. Irwin, M., McClintick, J., Costlow, C., Fortner, M., White, J., & Gillin, J. C. (1996). Partial night sleep deprivation reduces natural killer and cellular immune responses in humans. The FASEB journal, 10(5), 643-653.

  5. Imeri, L., & Opp, M. R. (2009). How (and why) the immune system makes us sleep. Nature Reviews Neuroscience, 10(3), 199.

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