Sleep is Good for Immune Health - Here's How to Get More of It

We have all experienced the power of a good night's rest; the feeling of waking up rejuvenated is hard to beat. Other than making you feel rested, sleep is also an important contributor to ensuring that your immune system is working at its best. In times of stress and uncertainty, focusing on getting enough sleep is especially important.

Most adults need about seven to nine hours of sleep, with older adults requiring a bit less, at seven to eight hours per night, according to the National Sleep Foundation.

In this article, we'll look at how getting adequate sleep strengthens the immune system, as well as the top five tips for improving your sleep hygiene habits to help you reach the goal of hitting the eight-hour mark.

Sleep and the Immune System

The immune system and sleep have a bidirectional relationship. When we are sleep-deprived, we are more susceptible to developing infections; when we have an infection, our bodies require more sleep, but it's not uncommon to have disrupted sleep during an illness.

In a study published in the journal Sleep of healthy adults who were subjected to the common cold virus, those who slept less than six hours per night were significantly more likely to get sick compared to those who slept seven or more hours.

The immune system is complex, with many different cells, proteins, and molecules working together to fight pathogens. When we sleep, many of the beneficial parts of our immune system are produced, which leads to a strengthened response when the body encounters a foreign invader.

When you're sleep deprived - whether for just one night or chronically - the body produces fewer cytokines, which are a family of signaling proteins that regulate inflammation and the immune response.

Two cytokines, interleukin-1 (IL-1) and tumor necrosis factor (TNF), are involved in sleep regulation, as the availability of them promotes sleep length and intensity. Levels of cytokines circulating in the blood peak during sleep and in the early morning hours. Thus, inadequate sleep would lead to insufficient cytokine production.

Inadequate sleep also leads to a reduction in T-cell proliferation and natural killer (NK) cell production, as well as a switch from anti-inflammatory to pro-inflammatory signaling pathways.

NK cells are white blood cells that fight bacterial and viral infections; sleep deprivation leads to a marked reduction in these critical immune cells. A December 1994 study published in Psychosomatic Medicine found that one night of partial sleep deprivation reduced NK cell activity by 72%; however, the NK cells were restored after getting adequate sleep the next night.

Lastly, sleep promotes T-cell production, which are white blood cells that play a significant role in how the body responds to viruses. When we are deprived of sleep, T-cell production is decreased, which increases susceptibility to viral infection.

Tips for Improving Your Sleep Hygiene

1. Keep Your Bedroom Cool.

If you want to get your best night's rest, your bedroom should be kept a little on the chilly side. Research has shown that people tend to sleep best at lower temperatures. The National Sleep Foundation recommends between 60 to 67 degrees Fahrenheit as the ideal range.

The science behind this is related to the circadian rhythm, which is the body's 24-hour internal clock. Body temperature tends to decrease in the evening before bed, with the lowest body temperature at around 4 a.m. A warm sleeping environment can disrupt this process, leading to poor sleep.

If that temperature range is uncomfortably low for you, try wearing socks to sleep. One small study found that sleeping with socks on led to improvements in sleep latency and quality.

2. Have a Consistent Bedtime Routine.

Maintaining a bedtime that doesn't vary by more than 30 minutes each night is helpful to train your body and mind to wind down for sleep. Not only does an inconsistent bedtime make it difficult to fall asleep, but it also increases cardiovascular disease risk factors.

You can choose calming activities to wind down, like a warm bath 90 minutes before bed or reading a book. Try to eliminate all blue-light emitting screens, like smartphones, computers, and tablets, for at least one to two hours before bed. If that's not possible, wearing blue-light blocking glasses can help to mitigate the deleterious effects of blue light on our nighttime melatonin production.

Similar to limiting the blue light at night, getting sunlight exposure in the morning can actually help you sleep better at night. The bright morning light reinforces our 24-hour circadian rhythm, leading to improved sleep quality and the ability to fall asleep more quickly.

3. Watch What You Drink.

It may seem obvious that we shouldn't drink espresso right before bed, but you may need to cut off the caffeine earlier than you think. Caffeine has a half-life of about six hours; this means that a 4 p.m. latte could still be in your system when you're trying to wind down for sleep. If you have trouble falling asleep, consider cutting off your coffee intake by noon.

You may also want to reconsider that nightcap. Although having a drink before bed may seem like it helps you to fall asleep faster, alcohol actually leads to poorer sleep because the body is unable to get into the restorative REM sleep phase that it needs to feel rested. Instead, opt for a calming chamomile tea, and see how your sleep improves.

4. Get Moving.

Low and moderate-intensity physical activity has been shown to improve various sleep outcomes. Higher-intensity exercise is also a sleep-promoter, as long as it's not done too close to bedtime.

A study published in the Journal of Sleep Research found that an exercise program consisting of 150 minutes per week of brisk walking led to significantly reduced insomnia symptom severity over six-months.

In another study, previously sedentary elderly adults who were randomized into an aerobic exercise group had increases in sleep duration and sleep efficiency, as well as increases in the anti-inflammatory cytokine IL-10.

5. Consider Sleep-Promoting Supplements.

If you're already practicing the previous four sleep hygiene tips and still aren't getting the rest you need, there are some supplements that can be helpful for falling asleep or staying asleep:

• Melatonin: The widely-used supplement melatonin may reduce the time it takes to fall asleep and increase overall sleep time, although studies have found mixed results.
• Magnesium glycinate: This highly absorbable form of the mineral magnesium helps with muscle relaxation and maintaining healthy levels of the neurotransmitter GABA, which is essential for restful sleep.
• Valerian root: A plant that comes in supplemental or tea form, valerian root may improve sleep by increasing GABA levels.
• L-theanine: This amino acid, found in tea and supplemental form, also promotes relaxation through GABA modulation; it has also been found to reduce stress and anxiety.

Key Takeaways:

• Sleep deprivation leads to disruptions in the normal immune response, leading to an increased susceptibility to infections.
• The main players involved with sleep and immunity are cytokines, natural killer cells, and T cells, all of which either work less efficiently or are underproduced during times of inadequate sleep.
• Improve your sleep hygiene by keeping your bedroom cool, having a consistent bedtime routine that doesn't involve screen time, limiting caffeine and alcohol before bed, and exercising during the day.
• Some helpful supplements for sleep include melatonin, valerian root, magnesium glycinate, and L-theanine.

References:

Abd El-Kader SM, Al-Jiffri OH. Aerobic exercise modulates cytokine profile and sleep quality in elderly. Afr Health Sci. 2019;19(2):2198–2207. doi:10.4314/ahs.v19i2.45

Hartescu I, Morgan K, Stevinson CD. Increased physical activity improves sleep and mood outcomes in inactive people with insomnia: a randomized controlled trial. J Sleep Res. 2015;24(5):526–534. doi:10.1111/jsr.12297

Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep Health. 2015;1(1):40–43. doi:10.1016/j.sleh.2014.12.010

Irwin M, Mascovich A, Gillin JC, Willoughby R, Pike J, Smith TL. Partial sleep deprivation reduces natural killer cell activity in humans. Psychosom Med. 1994;56(6):493–498. doi:10.1097/00006842-199411000-00004

Ko Y, Lee JY. Effects of feet warming using bed socks on sleep quality and thermoregulatory responses in a cool environment. J Physiol Anthropol. 2018;37(1):13. doi:10.1186/s40101-018-0172-z

Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep. 2015;38(9):1353–1359. doi:10.5665/sleep.4968

Valham F, Sahlin C, Stenlund H, Franklin KA. Ambient temperature and obstructive sleep apnea: effects on sleep, sleep apnea, and morning alertness. Sleep. 2012;35(4):513–517. doi:10.5665/sleep.1736

What is Sleep Hygiene? National Sleep Foundation website. https://www.sleepfoundation.org/articles/sleep-hygiene.