Simply put, your circadian rhythm is your body's internal clock. Operating on a roughly 24-hour cycle, it governs our sleep-wake cycle and plays a large part in everything from hormone release to body temperature. Circadian rhythms are not exclusive to humans and are found in nearly every living creature, from nearly every animal and plant to various micro organisms. Our circadian rhythms are regulated by a cluster of nerve cells in the hypothalamus known as the suprachiasmatic nucleus. This “master clock” of cells responds to, among other cues, light and, depending on how much is received, triggers such sleep-centric events as the release of melatonin.
When your circadian rhythm is disrupted, the immediate repercussions are that your sleeping, waking and digestive systems are thrown off; for lack of a better phrase you’ll, well, feel like crap. Longer-term effects include increased risk of cardiovascular events, obesity and, possibly, neurological problems like depression and bipolar disorder.
Are everyone’s rhythms the same?
Almost, but not quite. There are fluctuations in levels of alertness that everyone experiences (and can commiserate about) throughout the day—like that post-lunch slump that normally appears between 1:00 and 3:00 p.m. At night, our master biological clock makes us all sleepiest between 2:00 and 4:00 a.m. However, those ebbs and flows—including how intensely we crash in the afternoon—can vary by person. This accounts for some of us being “larks” and others “night owls,” despite the fact that we’re all diurnal creatures--active in daylight and asleep at night.
Circadian dips can also vary depending on how much sleep we’ve gotten the night before, and according to your life stage. Think about teenagers, who go to bed and get up later than adults. They usually feel more alert in the evening because their melatonin levels don’t naturally increase until later in the day, so they don’t really feel tired before 11:00 p.m. Their energy typically drops off at different times too—usually between 2:00 and 5:00 p.m. and 3:00 and 7:00 a.m. and can last even longer if they’re sleep deprived.
What throws your rhythm out of whack?
Traveling is a prime example. Changes in time zones, bedtimes and light cues confuse internal clocks, so travelers often arrive at their destination feeling jetlagged. But you don’t have to travel to throw your system out of whack; keep an irregular sleep schedule and you’ll feel the same effects.
Other rhythm-ruining culprits are your beloved electronic devices—computers, phones and tablets and being around artificial light sources before bedroom. All of these devices emit blue light, which trick your brain into thinking it’s daytime and delays the release of melatonin.
What can I do to keep my rhythms in order?
Maintain a consistent sleep schedule. Easier said than done, but sticking to regular bed- and wake-up time every day is paramount; even sleeping in late just one Saturday morning can throw off your body clock.
If you have trouble rising up in the morning, try opening your blinds and letting the sun in; that does double duty by resetting your circadian rhythm and delivering an energy boost by raising your body temperature and your cortisol level. It’s also important to get the best sleep possible, as your body clock is more sensitive than you might think.