Sleep still is a bit of a mystery. We understand more than ever, but why it is the way it is (long and cyclical), and exactly what it does and how it does it are still being discovered.
Whatever its exact functions are, we do know that our health—both physical and mental—relies on it. People who get poor sleep over long periods of time are more likely to be negatively affected by almost every other thing we worry about—chronic conditions, sickness, and cognitive impairment to name just a few. So its importance as a factor in our health is not nearly as ambiguous as what its definitive actions are.
Bottom line: sleep matters.
The question we’ve been asking with the last couple of blog posts is how does it affect your immune system? Aside from just telling you that the worse you sleep, the more likely you are to get sick, some research shows that sleep has a direct effect on important immune functions and that those immune functions also then have an effect on sleep.
There are two different important types of cells in your immune system—non-specific immune cells (natural killer cells) that have a general response to pathogens and specific immune cells, and T cells and B cells, that we get through exposure to specific pathogens.
Your natural killer cells kill cells that are infected with a virus without needing any prior exposure to the virus. Your B and T cells, however, require activation against a target by previous exposure to it. They can destroy cells infected with a certain virus because they’ve seen that virus before.
Then there are molecules called cytokines. Your different immune responses are coordinated by these molecules—they signal different immune and inflammatory responses—and elevated levels of cytokines can lead to inflammatory processes that promote plaque in your arteries. As important, though, is that cytokines are also involved in your sleep/wake regulation.
Your immune function varies throughout your sleep cycles. Your immune cells and cytokine levels peak at night and decrease in the morning. What some researchers think is that sleep involves reallocating resources from functions you use while you’re awake to maintenance functions, like the immune response to infections.
While this “scheduled” immune response is happening, those B and T cells are getting their exposure to pathogens and getting their programming to defeat them in the future. Extended periods of wakefulness may then have an impact on your body’s ability to train your immune system and resist pathogens.
What has been seen by researchers in the lab, is that sleep-deprived animals can not mount an immune response against bacteria that move from the intestinal tract into their organs and quickly succumb to infection. In humans, studies have shown that even four hours of deprivation for four nights produced poorer antibody response when those people were exposed to the flu. Even non-specific immune cells have diminished function in sleep-deprived individuals.
Not only does our immune system fail to get the adaptation it needs to reduce our risk of infection when sleep is poor, sleep deprivation and disturbances are associated with increased levels of cytokines which increase inflammation and can lead to inflammatory disorder, cardiac disorders, and more sleep disturbances.
Yes, the cytokine levels that increase with poor sleep and whose increased levels cause inflammation may also lead to more poor sleep. People with elevated cytokine levels have longer sleep latency (the amount of time it takes to fall asleep), a harder time falling asleep, poor sleep-to-wake ratios, and decreased deep sleep. That kind of disruption also causes increased levels of cytokines. It’s what you know as a vicious cycle.
Like I said at the start, we’re still learning much about sleep and some of these mechanisms may not work exactly like what I’ve written may suggest. Sleep and its maintenance roles play a part in the proper functioning of our immune system as shown in both animals and humans in various studies. Sleep disturbances can decrease our immune system’s adaptation to pathogens and also increase our cytokine levels which can lead both to the worsening of inflammatory conditions and to the further dysregulation of sleep.
How to improve your sleep (starting tonight)
The best we can do is continue to engage in practices that lead to better sleep like:
- Keeping regular bed and wake times
- Reducing evening exposure to blue light, especially by limiting the use of mobile devices and computers, but also by reducing blue light with blue blocking glasses, if possible
- Not eating within 2–3 hours before bedtime
- Avoiding stress in the evening as much as possible
- Engaging in practices that help us decompress mentally before bed like journaling, meditation, or breathing
- Maintaining a cool but comfortable temperature in the bedroom
- Using sleep-supporting supplements like magnesium at bedtime
- How to Boost Your Immune System: Part 1, Nutrition
- How to Boost Your Immune System: Part 2, Exercise