By Dr. Mercola
Researchers have learned that circadian rhythms—the 24-hour cycles known as your internal body clock—are involved in everything from sleep to weight gain, mood disorders, and a variety of diseases.
Your body actually has many internal clocks—in your brain, lungs, liver, heart and even your skeletal muscles—and they all work to keep your body running smoothly by controlling temperature and the release of hormones.
It’s well known that lack of sleep can increase your chances of getting sick. A new study shows just how direct that connection is.
The research found that the circadian clocks of mice control an essential immune system gene that helps their bodies sense and ward off bacteria and viruses. When levels of that particular gene, called toll-like receptor 9 (TLR9), were at their highest, the mice were better able to withstand infections.
Interestingly, when the researchers induced sepsis, the severity of the disease was dependent on the timing of the induction. Severity directly correlated with cyclical changes in TLR9.
According to the authors, this may help explain why septic patients are known to be at higher risk of dying between the hours of 2 am and 6 am.
Furthermore, they also discovered that when mice were vaccinated when TLR9 was peaking, they had an enhanced immune response to the vaccine. The researchers believe vaccine effectiveness could be altered depending on the time of day the vaccination is administered…
According to study author Erol Fikrig, professor of epidemiology at the Yale School of Medicinei:
“These findings not only unveil a novel, direct molecular link between circadian rhythms and the immune system, but also open a new paradigm in the biology of the overall immune response with important implications for the prevention and treatment of disease. Furthermore, patients in the ICU often have disturbed sleep patterns, due to noise, nocturnal light exposure and medications; it will be important to investigate how these factors influence TLR9 expression levels and immune responses.”
Lack of Sleep Worsens Stress-Related Immune Depression
One of the first studies to provide direct evidence linking sleep with the human stress-immune relationship dates back to 1998ii. Stress is also known to interfere with immune system function, and has been found to increase susceptibility to the common cold and slow wound healing.
In that 1998 study, the researchers discovered that people who were more likely to awaken during the first sleep cycle also tended to have lower levels of natural killer cells (NKC). Overall, the age of the patient was the greatest determinant of NKC level, but sleep disturbances were responsible for about 12 percent of the variance in NKC level.
Are You Living in Sync with Your Natural Body Clock?
Sleeping well is one of the cornerstones of optimal health, and if you ignore your poor sleeping habits, you will, in time, pay a price. In general, you will feel best and maintain optimal health when your lifestyle is in line with your circadian rhythm. It’s wise to establish healthful routines of eating, exercising and sleeping, and to stick to them every day, including the weekends.
Unfortunately, sleep deprivation is such a chronic condition these days that you might not even realize you suffer from it. Your circadian rhythm has evolved over many years to align your physiology with your environment. However, it operates under the assumption that you are behaving as your ancestors did. Historically, humans have slept at night and stayed awake during the day. If you stay up late at night, depriving yourself of sleep, you send conflicting signals to your body.
As a result, you body gets confused and doesn’t know whether it should be producing chemicals to help you sleep, or gear up for the beginning of a new day.
Melatonin is another chemical closely tied to your circadian rhythm. It’s a pineal hormone and a very potent antioxidant, created in your brain during sleep.
Among its many functions, it slows the production of estrogen and is well known to suppress tumor development, which is why insomnia may increase your risk of cancer. Melatonin also helps suppress harmful free radicals. Melatonin production can be severely disrupted simply by exposing yourself to bright light late at night. Just switching a bedside lamp on and off in an otherwise pitch-black room produces a drop in melatonin levels. This is why it’s so important to turn off the lights as the evening wears on, and avoid watching TV and working on the computer late at night.
How Sleep Influences Your Physical Health
Without good sleep, optimal health may remain elusive, even if you eat well and exercise (although those factors will tend to improve your ability to sleep better). Aside from directly impacting your immune function, another explanation for why poor sleep can have such varied detrimental effects on your health is that your circadian system “drives” the rhythms of biological activity at the cellular level. Hence disruptions tend to cascade outward throughout your entire body. For example, besides impairing your immune function and raising your cancer risk, interrupted or impaired sleep can also:
| Increase your risk of heart disease. | Harm your brain by halting new cell production. Sleep deprivation can increase levels of corticosterone (a stress hormone), resulting in fewer new brain cells being created in your hippocampus. |
| Aggravate or make you more susceptible to stomach ulcers. | Contribute to a pre-diabetic state, making you feel hungry even if you’ve already eaten, which can wreak havoc on your weight. |
| Raise your blood pressure. | Contribute to premature aging by interfering with your growth hormone production, normally released by your pituitary gland during deep sleep (and during certain types of exercise, such as high intensity interval training). |
| Worsen constipation. | Increase your risk of dying from any cause. |
Furthermore, lack of sleep can further exacerbate chronic diseases such as:
