There is an old proverb that says “timing is everything.” Living organisms across the tree of life, including humans, have been using this to their advantage. From plants and animals, to fungi and cyanobacteria, each organism has a built-in, self-sustained 24-hour rhythm driven by a circadian clock.
These biological rhythms are dictated by external cues called zeitgebers, mostly light and temperature. Put simply, these cues harmonize the internal clocks of living organisms with external environmental time. For millions of years, plants and animals have had no problem getting in sync with the Earth. Most animals sleep at night to rest and conserve energy and plants don’t just wait for sunrise to bloom or spread their foliage; they anticipate the dawn.
Animals that migrate across continents can reset these time systems according to the time zone and climate of their destination. Only in exceptional circumstances, such as laboratory manipulation of zeitgebers do their timing systems don’t harmonize with the Earth’s time.
In people, light is the main synchronizer of the circadian rhythm. Our eyes have over 5,000 sensors that sense blue light from our surroundings and send that information to a “master clock” in our brain. This “master clock” then synchronizes with each cell in the body through hormonal signals.
This is explains why in the morning, when we open our eyes and start our day, we feel more alert and happier. At night, these sensors are no longer active, causing us to be less active until we fall sleep.
In the present day, however, we’ve found ways to activate these sensors at night and suppress sleep. We keep our lights on longer than we should, we watch TV, work in our computers, or thumb through our phones past our bedtime. Across many parts of the globe, particularly in cities, people work throughout the night and sleep throughout the day. Apart from light, there’s also another time synchronizer that we’ve managed to control: temperature. We can create ideal temperatures in our homes and workplaces to suppress or encourage sleep.
Effects of Circadian Disruption on Human Health
It’s becoming clear that this internal clock has a profound effect on our health and physiology. Mounting evidence suggests that the disruption of our circadian systems is associated with adverse health consequences. It’s not a simple of case of losing track of time. It’s affecting our metabolism, brain function, mood, and all the other bodily functions that are regulated and controlled by our circadian rhythms.
A study led by Joseph Takahashi, an American geneticist and neurobiologist at the University of Texas Southwestern Medical Center, found that people with prolonged sleep deficit experience social jetlag. Social jetlag is the absence of sleep regularity that’s so alarmingly common among people across demographics. This condition has wide-ranging implications, including chronic fatigue, obesity, poor cognitive performance, mentall illness, and many more. It can also increase your risk for heart disease, cancer, diabetes, and a host of other life-limiting diseases.
Why Are We Losing Sleep?
The idea that having enough sleep can make you healthier and happier is nothing new. It’s one of the first lessons we learn at home and from school. Despite it being the least expensive way to lose weight or delay a visit to the doctor, how come we force ourselves to watch another episode of our favorite show on Netflix or pull out an all-nighter to study for upcoming exams? Why are sleep disorders so common when our internal clock is like that of other organisms in their organization and response to light?
A study conducted by Jeanne F. Duffy and Charles A. Czeisler of Harvard Medical School’s Division of Sleep and Circadian Disorders revealrs that humans are unlike organisms in terms of their response to varying intensities of light. It turns out that our eyes’photoreceptors are more sensitive during our biological night. So when you’re watching TV or playing a game on your tablet at night, the blue light these devices emit are making you even more alert than you are when exposed to daylight.
There are a number of different factors, of course, but behavioral modification is the most common reason our biological clocks get messed up. Eating at night or drinking coffee before bedtime, for instance, reduces the release of melatonin, the sleep hormone. So do other social cues, like talking to someone or reading an absorbing book.
When these habits become ingrained and a person remains out of sync with his or her body clock, a host of problems may arise and become permanent. This is especially problematic among people on night work shifts. Though the effects of circadian disruption on night shift workers have not been adequately studied, but approximately 25 to 30 percent of shift workers experience symptoms of insomnia or excessive sleepiness. Evening shift work is also associated with a 29 percent increased risk of becoming obese or overweight.
Tip: Follow the Light
So how do we harmonize with our internal body clocks? Almost all sleep scientists suggest that it can be as simple as going to bed at night and staying awake during the day. Don’t fight sleep when you have the change; your body needs it to heal itself and give you energy during your waking hours. If you’re feeling that dip in alertness during the day at work, take a nap or go outside and bask in the sun.
For people who have trouble sleeping, particularly those with chronic sleep disorders, therapeutic intervention and alternative treatments may be necessary. Melatonin, the hormone that regulates sleep and wakefulness, is one option. Melatonin tablets have proved to be effective in helping totally blind people sleep, and they prove to be beneficial to people with delayed sleep phase and circadian rhythm sleep disorders.
Using the “night shift” feature on your smart phone is recommended, but not using your phone an hour before you hit the sac is a time-and-tested trick.
There is so much to explore about sleep medicine and circadian biology. But already, it seems to provide the simplest answer to the questions that keep us up at night: “How do I fight diseases?” or “How do I become happier?” or “How do I perform better at work or school?” Of course, having enough sleep regularly doesn’t make you invincible or the best person you can be, but it helps tune your mental, emotional, and physical health, which can only lead to good things.
So listen to the music of your cells, follow the light from the sun, and pay attention to the internal rhythms of your body. It’s one of the secrets to a long, healthy life.