You probably think of yourself as either a “morning person” or a “night owl”—and when it comes to your health and even your survival, the distinction might be crucial.
Emerging research on the body’s circadian rhythms shows that everything from our gut health to our bodies’ healing powers to our response to medications and even the outcome of surgery is directly affected by our biological clocks.
Sound far-fetched? It’s not. The 2017 Nobel Prize in Physiology or Medicine was awarded to three American scientists for their groundbreaking research into the impact of the hundreds—even thousands—of ticking clocks buried deep inside our organs, tissues and cells.
Latest compelling evidence: A study published in The Lancet found that patients who undergo heart-valve replacement surgery in the afternoon are 50% less likely to suffer major cardiac events during the following 500 days compared with people who undergo the procedure in the morning—a huge difference in success rate. This finding builds on previous research showing that adults are most likely to suffer heart attacks in the morning rather than at night.
It’s merely one example of the vast potential of the burgeoning field of chronobiology, the study of how living organisms respond and adapt to the daily 24-hour rhythms of life. Researchers have identified hundreds of genes that show a time-of-day pattern in heart tissue alone, and they appear to be important for healthy heart function.
Sleep, which is heavily impacted by natural light and darkness, also can be adversely affected when we alter our circadian rhythms. If you’ve ever traveled across multiple time zones, you’ve experienced what it feels like when the body’s internal clocks are disrupted.
And that’s only scratching the surface. Other links are being discovered between circadian rhythms and…
• Gut health. Trillions of bacteria in your gastrointestinal (GI) tract, known collectively as the microbiome, play a vital role not just in digestion but also in overall wellness. Now researchers are investigating whether circadian disruption adversely affects these bacteria.
The notion of the microbiome having its own circadian clocks comes from studies of late-night shift workers, many of whom are prone to developing GI problems related to sleep deprivation. In addition, multiple universities are researching rodents and humans to determine whether consuming probiotics (good bacteria) and prebiotics (plant fiber that feeds these probiotics) helps protect the microbiome from the effects of circadian disruption.
If confirmed, these studies might one day shield shift workers, members of the military (who frequently operate under sleep-deprived conditions) and typical night owls alike from digestive disorders—not to mention obesity, diabetes, heart disease and a host of other conditions linked to chronic sleep loss.
• Wound healing. Skin cells called fibroblasts that aid in healing are thought to function more efficiently during the day than at night because of circadian clocks in the skin that are more active during daylight hours.
A 2017 study published in Science Translational Medicine found that cuts and burns heal nearly 60% faster when the injury occurs during the day than at night. This may be an evolutionary advantage dating back to prehistoric times. Ancient humans were more likely to be injured during the day, when they hunted prey for that evening’s dinner.
If chronobiologists can further pinpoint optimal times of day for different people’s healing, patients may one day be able to schedule surgery at those particular hours, improving their odds of a speedy recovery.
• Asthma symptoms. For people with asthma, symptoms tend to worsen at night and in the early morning hours. Considering this, researchers have investigated the effectiveness of timing medication precisely to ease symptoms, an—approach called chronotherapy.
Examples: Asthma drugs classified as leukotriene receptor antagonists, such as montelukast (Singulair) and zafirlukast (Accolate), are most effective at improving symptoms when taken in the evening, according to a 2011 study published in Thorax.
Similarly, taking a single dose of an inhaled corticosteroid at 5:30 pm was found in research published in 2013 in Indian Journal of Pharmacology to be nearly as effective as four doses spread throughout the day.
• Diabetes. Research suggests that the link between poor sleep and diabetes may have to do with the fact that if you’re awake when your body’s master clock thinks you should be sleeping, your body becomes less sensitive to insulin—a precursor to diabetes.
In a 2015 study published in Current Biology, five days with just five hours of sleep per night results in a 20% reduction in insulin sensitivity in otherwise healthy adults. That’s because if you go to bed late, wake up early and eat breakfast, your pancreas will release insulin as it should, but the body is less responsive to it because melatonin levels are still high, as if you were sleeping. Result: Your blood sugar remains elevated, and your body continues overproducing insulin. This won’t cause diabetes after just a few nights, but chronic poor sleep is certainly a risk factor.
• Depression. Daily early-morning exposure to bright light (also considered a type of chronotherapy) has been shown to rival the therapeutic benefits of antidepressants in people with major depression…and even to help major depression patients for whom such drugs have not been effective.
• Cancer. Decades’ worth of clinical trials have found that strategically timed chemotherapy can shrink tumors more effectively and boost survival rates from certain types of cancer, including colorectal cancer and lung cancer—and even may reduce chemo’s toxic side effects.
Important finding: Cancer cells tend to be less active at night than during the day, and it may be that evening chemotherapy sessions improve the odds of successfully targeting those cells because they are less active, according to research published in 2007 in Advanced Drug Delivery Reviews.