What is Circadian Rhythm and How Does it Impact Our Health?

I’ve mentioned in several of my blogs about the importance of maintaining a good circadian rhythm for optimal sleep and wakefulness. In this blog, I’ll describe how this master clock in our body influences our daily pattern and its importance in keeping this internal rhythm balanced and healthy.

Your circadian rhythm is your 24-hour cycle that is part of your body’s internal clock that carries out essential functions and processes. It is controlled by your hypothalamus and translates signals from the environment to your body. Your rhythm is influenced by external factors like light and your body can regulate temperature and metabolism to keep you alert or help you fall asleep.

Your sleep-wake cycle is part of your circadian rhythm and during the day, light exposure sends signals to your brain to be awake, alert and active. When your brain detects darkness at night, it stimulates the production of melatonin which is a hormone that promotes deep sleep. And it is this alignment of day-wakefulness and night-sleep that maintains a healthy cycle of your body’s circadian rhythm.

The word “circadian” comes from the Latin phrase “circa diem” which means “around a day” and this rhythm works to ensure that the body’s processes are optimized during the 24-hour cycle. Just as the circadian rhythm of a flower determines when they open up during the day and close at night, the same goes for us humans with our mental and physical systems in sync throughout the body during this cycle. For example, our circadian rhythm tells us when to regulate our digestive system, temperature and hormones to manage our metabolism and energy expenditure. Our circadian rhythms are closely connected to day and night – light is the most powerful influencer on our hypothalamus and impacts how this part of the brain interprets signals to regulate our body’s activities. 

Disruption of the circadian rhythm not only leads to sleep disorders but research is now revealing how it impacts physical and mental health like obesity, diabetes, depression and mood. Studies have shown that circadian rhythm disruption can lead to cognitive impairment and metabolic syndrome as well as psychiatric illness and age-related dementia.

The most common causes of circadian rhythm disruption are due to:

• Traversing multiple time zones and suffering from jet lag due to not being adjusted to the new day-night cycle of your destination. The easiest way to get acclimated is to try to quickly adapt to the new clock upon reaching your destination.
• Working the night shift as this will always disrupt circadian rhythm – it will be hard to adjust even if you sleep in complete darkness during the day. My mom worked the night shift for 25 years and I am convinced that her Alzheimer’s was directly impacted by this long-term disruption to her circadian rhythm.
• Going to bed very early and also waking up early (before sunrise). This is more prevalent in older adults but one percent of the population have this sleep phase disorder. 
• Night owls who stay up late and then sleep late into the morning. This is more typical of teenagers but this delayed sleep phase disorder also impacts a small percentage of the adult population.

Maintaining a healthy circadian rhythm is critical to getting good sleep at night and functioning at your peak during the day. Here are some good habits to establish:

• Aim to always sleep in the dark as even the tiniest amount of light can disrupt your circadian rhythm and production of melatonin and serotonin. Use blackout curtains and remove (or put electrical tape over) any remaining light.
• Keep your room temperature lower than 72 degrees (between 60 and 68 degrees Fahrenheit has been shown to be optimal). When you sleep, your body’s internal temperature drops to its lowest level, generally about four hours after you fall asleep. So it’s no surprise that this cool environment is conducive to sleep as it mimics your body’s sleeping temperature. It helps your body regulate not only melatonin but also cortisol and growth hormone levels.
• Avoid caffeine after 2pm. It’s been shown that for people that are slow metabolizers of coffee, the caffeine effects last long after the drink. Stick to organic decaf if you need that cup-a-joe. Also, be mindful of products and medications that contain caffeine.
• Finish eating at least three hours before bedtime – the rise in blood sugar levels after a meal will delay sleep and laying down soon after a meal can increase the risk of acid reflux. Also avoiding foods that you may be sensitive to (like dairy, sugar and certain grains) could help reduce gastrointestinal upset, bloating, gas and the late night trips to the bathroom. If you notice that you have digestive issues, you might explore discussing your nutrition with a registered dietitian as addressing any possible food sensitivities can have a profound effect on digestion and sleep.
• Make sure to get regular exercise (at least 30 minutes a day) as it can improve your sleep – but get it done at least three hours before bedtime so you don’t get the second wind from the exercise high. This study done by the National Sleep Foundation has shown that those who do moderate to vigorous exercise regularly reported higher quality sleep than non-exercisers.
• Get sunlight in the morning. It will adjust your circadian rhythm to help you sleep better at night. Try to get at least 30 minutes outside every day – morning is best when the sun is less intense.
• Stick to a consistent bedtime (even on the weekends) and aim to get to bed early so that your body maintains a good sleep rhythm. Deep sleep happens in the first half of your night so it’s important not to miss this time window which is when your body repairs and recharges.
• Try to avoid doing work or watching TV in bed. It will be harder for your body to relax when it’s time to sleep – it’s important to keep your work space separate from your sleep space. Avoiding blue light from electronics close to bedtime is important as it’s been shown that blue light can delay sleep, suppress melatonin secretion and impair next-morning alertness. If you must watch that episode to wind down, try blue light blocking glasses and/or a blue light filter for your device. Here are some to try: Blue Light Blocking Glasses
• If you need an afternoon snooze, make sure to keep naps short (20-30 minutes) and earlier in the afternoon so it doesn’t push back your bedtime and throw off your schedule. 

While establishing good sleep hygiene can help you maintain a good circadian rhythm, there may be other circumstances that can prevent you from getting optimal sleep. If you have persistent sleeping issues and/or daytime drowsiness, speak to your doctor or seek out a sleep specialist to dig deeper into the cause to get to the root of the problem.