If you were living in a cave or in deep space with no light-dark cycle, no clocks, and no social cues, then your body’s internal clock that creates your sleep-wake pattern would tend toward a 28-hour cycle. This means the internal signals from your own physiology, without external influences, tend not to match the earth’s daily 24-hour cycle.

Fortunately, our bodies are equipped with mechanisms that adjust. Not only do we adjust to the cycle of the earth’s daily rotation, we also can adjust to other patterns, like when the cat wants to be fed, when the dog needs to go out, when the children wake up, or when the job requires our presence. But while the human sleep-wake cycle is remarkably flexible, it does have its limits.

At its core, the sleep-wake cycle is just that, a cycle, and it operates best when it follows a pattern. When we provide it with randomness, chemical interferences, or conflicting signals, that pattern can become distorted. This distortion can lead to poor sleep quality, insufficient sleep quantity, and even sleep disorders like insomnia.

Knowing what influences your sleep cycle will enable you to understand what disrupts it, as well as to know what you can do to support good sleep. The following five things have significant influence on the body’s ability to feel awake or sleepy when it should, and to get a restful night’s sleep when it’s time. 

1. Light

You have probably noticed that daylight influences how wakeful you feel. A long, bright summer day can make you feel energetic and productive, while a short, bleak winter day can make you want to curl up with a blanket and sleep, even if everything else is the same. These day-length changes can be so influential that some people experience seasonal affective disorder (SAD) – a form of depression that tracks with day length. Depending on where you live, the amount of sunlight you are exposed to can have a major effect on your sleep-wake cycle. 

Artificial light can effectively mimic longer days. In fact, light therapy is a treatment for SAD. Many artificial light sources can mimic sunlight fairly closely. This can make it easier to read, create art, and appreciate indoor environments, but it also has the effect of tricking the body into thinking it’s still daytime long after the sun has gone down.

In the dead of winter this can be helpful, but when we use lighting without knowing its effect on our sleep, it can become disruptive. Most of us are also surrounded by electronic devices that have small lights on day and night, and outdoor lighting we can’t control, leading to an environment that is not ever truly dark.

Supporting good sleep

Be mindful of how long you leave bright lights on at night. Begin turning off brighter lights, especially those with broad spectrum or cool, blue hues, as you get closer to bedtime. This includes digital screens like tablets and TVs. An hour before you want to sleep, reduce ambient lighting to a minimum, and choose warmer, yellow-hued light. In the room where you sleep, reduce ambient lighting by removing or safely covering sources of light (like device LEDs) and use blackout curtains to block outside light. Wearing a sleep mask is a great alternative for individuals who need to use night lights for safety or who can’t reasonably reduce bedroom light. 

2. Hormones

Melatonin is the most widely known hormone related to sleep. Its production is influenced by light, resulting in higher levels when it’s dark and lower levels when it’s light. The up-and-down cycling of melatonin is a major component of your sleep-wake circadian rhythm, and it helps prepare your body for sleep.

Another hormone that influences sleep is cortisol, the “fight or flight” hormone associated with stress. Modern lifestyles often result in long-term, continuous stress, which can cause cortisol levels to remain high. Elevated cortisol raises blood glucose; suppresses your immune, digestive, and reproductive systems; affects mood; and interferes with restful sleep. 

Supporting good sleep

Managing artificial light exposure as noted earlier helps avoid disruptions to your natural melatonin cycle. Managing cortisol levels is directly related to managing stress and supporting good sleep. Regular exercise, addressing other sleep disruptors, and learning coping mechanisms for stress can balance your cortisol and melatonin levels and improve your sleep.

Thorne’s Sleep Test measures melatonin and cortisol patterns over a 24-hour period, and it comes with a diet, lifestyle, and supplement plan based on the test’s results. Don’t want to take a test right now? If your body needs extra sleep support, then check out our Sleep Bundle. Melatonin supplements like Melaton-3 or Effusio’s Sleep + which contains melatonin, chamomile, and L-theanine,  support restful sleep and help balance a disrupted circadian rhythm.* Still not sure which supplements might be best for you? Try our Sleep Quiz and Stress Quiz

3. Chemicals

A wide variety of chemical substances can influence your sleep-wake cycle, including caffeine, nicotine, alcohol, and over-the-counter and prescription medications. Caffeine keeps you awake by blocking sleepiness signals in the brain. Nicotine is a stimulant. Although alcohol can make you feel sleepy, it interferes with melatonin and other sleep-regulating systems, disrupting your ability to get deep, restful sleep. Many medications, like decongestants and blood pressure drugs, can disrupt your quality of sleep or your ability to fall asleep.

Supporting good sleep

Avoid substances known to have a negative influence on sleep, especially at the end of the day. If you do use them, then take your final dose four hours before bed (two hours might be enough for nicotine). For some individuals, it will take even longer to clear the effects, so get to know how each substance impacts you and adjust accordingly.

Also, be sure you understand how your medications can interfere with your sleep and discuss strategies with your health care practitioner if you think a medication is costing you needed rest. If you’re looking for a replacement for that habitual nightcap, then try chamomile tea or warm milk.

4. Distractions

Sleep is prone to disruption from distractions. Distractions can come from external stimuli like noise, movement, or an uncomfortable room temperature, and from internal stimuli like pain, stress, anxiety, depression, or other mood disorders. Even if these things don’t keep you awake, they can degrade your quality of sleep by causing you to have difficulty falling asleep, wake up often, or get less deep, restful sleep. 

Supporting good sleep

Noise can be masked with ear plugs or white noise. If significant snoring is an issue for you or your sleep partner, then seek assistance from a health care practitioner because snoring can degrade sleep quality – and can be a sign of something more serious, such as sleep apnea. Turn down the thermostat at night or use lighter covers.

If disruptions come from a pet, then keep it out of your sleeping space (I know…) and give them extra attention during the day instead. If your sleep partner’s movements are disruptive, then consider ways to adjust your sleep arrangement to minimize how much you notice them, like switching to a mattress that masks movements or using separate covers. Addressing pain and mood are also important components of getting healthful sleep.

5. Activity

What you do during the day can impact your sleep, but the time before bed especially influences your ability to fall asleep when you want to. You have likely experienced difficulty falling asleep after an exciting event, vigorous exercise, or an engrossing movie. Most of us need some transition time between the activities of the day and sleep. 

Supporting good sleep

Scheduling time to wind down before going to bed, especially after an exciting or stressful event, helps to transition to sleep faster. For most individuals, exercising earlier in the day and avoiding strenuous exercise for at least an hour before bed can provide increased daytime energy and more restful sleep.

Ultimately, good sleep depends on a cycle with a rhythm. As you’ve seen, this rhythm can be disrupted in many ways. Whether you call it good sleep hygiene, a bedtime routine, or healthy sleep habits, an important way to support quality sleep is to follow a pattern. Going to bed and waking up around the same time each day (not just on weekdays) are powerful tools for supporting a healthy circadian rhythm and quality sleep.

Next time you wake up not feeling rested, wake up frequently during the night, or have trouble falling asleep, determine how the above five things are influencing your daily patterns and make smart adjustments to bring yourself back to quality sleep.