Unlocking the Power of Circadian Health: How Light, Sleep, and Timing Shape Your Wellbeing

Sleep is part of the roughly 24-hour cycle of our body’s natural rhythm known as the circadian rhythm. In fact, the circadian rhythm is also referred to as “the sleep-wake cycle.” Though sleep is a big part of it, the circadian rhythm encompasses much more than just sleep - it also affects digestion, hormonal balance, energy levels, immune function, and more. You can think of the circadian rhythm as your internal clock, with different physical functions beginning and completing their cycles at different times of the day. That internal clock is heavily influenced by light and dark - the presence or absence of light tells the clock when to reset. In the absence of a consistent or healthy circadian rhythm, the physical processes that align with the circadian rhythm get disrupted, which can majorly impact people’s day-to-day. With so many fundamental physical processes that the circadian rhythm impacts, it’s easy to see why circadian health is important to prioritize. Getting a full night’s sleep is half the battle, but what you might not be aware of is how light exposure can help or hinder the quality of your sleep. With the goal of helping you prioritize your circadian health effectively, this blog will highlight the importance of a healthy circadian rhythm, and discuss how light powerfully affects circadian health. 

What Circadian Health Impacts

Circadian rhythms impact almost every system of health that we at Frequency prioritize supporting: Cardiovascular health, circadian health, cognitive health, and emotional sustainability. The studies outlined below have helped shape our understanding of circadian health and showcase why we at Frequency promote the prioritization of a healthy circadian rhythm.

Cardiovascular Health

Circadian health has been shown to impact the cardiovascular system - circadian disruption is associated with an increased risk of dyslipidemia, obesity, and insulin resistance, meaning that a stable circadian rhythm could decrease risk in those areas and support a stronger cardiovascular system (1).

Circadian Health

Nearly every tissue and organ in humans abides by its own circadian rhythm, and they’re collectively calibrated to the cycle of the sun (2). Thus, by prioritizing the health of your sleep cycle, you’re also affecting the health of each tissue and organ that is tuned to the sleep cycle.

Cognitive Health

Circadian health also affects cognitive health: in a 2004 study, participants with disordered circadian rhythms were found to have slower reaction times (3). Additionally, their reaction times were sensitive to changes in homeostatic sleep pressure (the physical need for sleep) (4).

In a 2021 study, processes related to prefrontal cortex functions were found to be affected by even a single night of sleep deprivation (5).

In a 2015 study, global cognitive performance scores, including memory and learning, were poorer in night shift workers compared to day shift workers, and cognitive impairment effects took up to 5 years to reverse (6).

A 2016 study found that the hour of sleep lost during the daylight savings change in spring is correlated with a 24% increased risk of ischemic stroke, while the hour of sleep gained during the fall daylight savings change is correlated with a 21% decreased risk of ischemic stroke (7).

These studies indicate that a healthy circadian rhythm can support cognitive health and boost cognitive functions like reaction time, memory, and learning.

Emotional Sustainability

Circadian health can also affect emotional sustainability: A 2018 study indicated that patients with disordered circadian rhythms were more likely to suffer from lifetime major depressive disorder and lifetime bipolar disorder, and to feel lonelier and more neurotic (8).

The findings of this study suggest that a healthy circadian rhythm might reduce the risk of lifetime major depressive disorder and lifetime bipolar disorder, and decrease feelings of loneliness and neuroticism. In fact, sleep problems are so interrelated with poor mental health that it’s clear they impact each other - poor mental health can cause sleep problems, and sleep problems can cause poor mental health.

Since light is the primary signal that governs our circadian rhythms, intentionally aligning our routines with the cycle of the sun can help boost our circadian health.

How to Support a Healthy Circadian Rhythm

So, granted that a healthy circadian rhythm is so important, you might be wondering how to support circadian health. The key is light exposure. Since light is the primary signal that governs our circadian rhythms, intentionally aligning our routines with the cycle of the sun can help boost our circadian health. Additionally, paying attention to the type and intensity of light we’re exposed to at different times of the day can also have a notable effect on our circadian health.

For example, exposing yourself to bright, intense light right before bed can disrupt your circadian rhythm. The body is designed to wind down as light decreases - lower, less stimulating light later in the day does not inhibit natural melatonin production, so if we avoid bright, stimulating light at bedtime, we are able to naturally feel the pressure of the onset of tiredness, and feel tired enough to go to sleep when our bodies need to.

One way to help support your circadian rhythm is by using red light night lights. Blue light is a high-frequency light that blocks the body’s production of melatonin, so by using red lights at night, you can avoid the disruption of melatonin production, supporting a healthy circadian rhythm.

However, it should be noted that blue light isn’t a net negative - in fact, blue light exposure in the morning can help you feel more alert and energized earlier in the day.

Another tool that can help support a healthy circadian rhythm is a SAD (Seasonal Affective Disorder) Light. SAD lights are intended to be used in the morning, exposing you to high-intensity, high-frequency light, acting as a pseudo-sun. For this reason, SAD lights can be especially helpful in the winter months, when the sun is often hidden behind clouds and the days are shorter. Typically, SAD Lights should be used on cloudy mornings to help you feel energized and alert in absence of the full brightness of the sun.

Given its comprehensive effect on so many different facets of health, both mentally and physically, it’s easy to see why circadian health is important and should be prioritized. To learn more about circadian health and its effects, check out Episode 13, Episode 18, and Episode 19 of the Finding Frequency Podcast.