Ever wonder why our natural sleep cycle seems to mirror the sun? The effect of light on our brain is more powerful than you might think, due to a biological process called circadian rhythm. Light is at the centre of regulating this process, which means the amount of light we expose ourselves to at certain times of day has a direct affect on our sleep.
The body’s natural circadian rhythm is a powerful tool for regulating hormonal function, digestion, and sleep patterns. Using environmental cues like sunlight, our brains release hormones signalling whether we need to be alert or at rest. But it’s easy for this rhythm to get out of sync if we fall into disruptive habits in our routines.
What is “Circadian Rhythm”?
Circadian rhythms are natural cycles that repeat every 24 hours, in which the body responds to the environment around it. This happens primarily through the light-dark cycle, by exposure to light. This cycle is managed by a part of the brain in the hypothalamus known as the circadian pacemaker, and is heavily influenced by the input received from our eyes. The amount of light we’re exposed to throughout the day (and at what times) directly affects when our brain releases the hormones that control our sleep patterns.
When we’re exposed primarily to natural light throughout the day, our body’s circadian rhythm naturally aligns with sunrise and sunset. However, with electricity allowing us to be surrounded by light at all times of day our circadian pacemaker can easily be affected, resulting in changes to our sleep cycle. Being surrounded by artificial light later in the day pushes our sleep cycle later, while light in the morning shifts it earlier. This misalignment with the natural day-night schedule can result in troubling health issues such as worsened metabolism, cardiovascular problems, weight gain, and even an elevated risk of cancer.
Melatonin
Melatonin is the primary hormone used by the brain to regulate sleep, and is made by the body in response to light exposure. The pineal gland in the brain responds to darkness by increasing production of melatonin, which results in the feeling of drowsiness. Light exposure halts this production, and helps to increase alertness. Artificial light in the evening can halt the cycle, pushing our wake-sleep schedule back and disrupting our circadian rhythm. It can also reduce the quality of your sleep by inhibiting the transitions between REM sleep cycles while asleep.
Causes for circadian rhythm disorders
Seasonal Affective Disorder - A common type of depression that affects people who live in cold climates with shorter days in the winter. This form of circadian rhythm disruption comes from decreased daylight hours and affects your mood. A way to combat this disruption is using a ‘SAD’ lamp, which simulates sunlight to regulate your circadian rhythm during months when daylight hours are short.
Jet lag - A form of circadian rhythm disorder that arises from travelling across multiple time zones. Your internal clock struggles to adjust to the new time zone, causing problems with staying awake or falling asleep at appropriate times. Typically, adapting to the new time zone requires daylight exposure at specific times to realign your circadian rhythm with that of the new environment.
Shift work - The Office for National Statistics reports that 27% of the UK work night-time shifts. Reversing your sleep cycle to be awake during the dark hours can have significant impacts on your health. Due to the disruption of your circadian rhythm, shift work is linked with an increased risk of occupational and driving accidents, sleep problems, and long term health conditions.
How to improve circadian rhythm alignment
Here at healf we know the value of good sleep hygiene and the lasting effects it can have on your health. Understanding your circadian rhythm helps to achieve better sleep quality. Here are some tips to making sure your sleep routine promotes a healthy circadian rhythm.
Morning sun exposure - Being in the sun first thing in the morning is great for setting your internal clock ahead. As little as 15 minutes of daylight in the morning can be the boost you need. Go for a walk, sit outside, even drink your morning coffee by a window! Cloudy days can still provide the daylight needed to align your circadian rhythm.
Limit screen time at night - Eliminating technology use the hour before you go to sleep is ideal for limiting exposure to the blue light that throws off your circadian rhythm. Using blue light glasses, turning down the brightness, and keeping your devices silenced during the night are all beneficial to your sleep hygiene. The less artificial light you’re exposed to at night, the better.
If you’re looking for some help maintaining healthy sleep hygiene, here are some products we recommend.
By April Greider for Healf Journal
Sources
- https://nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx#:~:text=Circadian%20rhythms%20can%20influence%20important,Body%20temperature
- https://pubmed.ncbi.nlm.nih.gov/22526883/
- https://www.sleepfoundation.org/bedroom-environment/light-and-sleep
- https://www.ons.gov.uk/businessindustryandtrade/business/activitysizeandlocation/articles/thenighttimeeconomyuk/2022#:~:text=In%202022%2C%20it%20was%20%22usual,only%20work%20during%20the%20day
- https://www.webmd.com/sleep-disorders/features/morning-light-better-sleep
