Sleep Hygiene Explained: The science behind why it works!

Written by Emily Nason, Psychologist, Synapse Psychologist

“Sleep is the golden chain that ties health and our bodies together” Thomas Dekker.

Sleep hygiene has gained attention recently, but many of us do not fully understand the science behind it. The basic formula for sleep is straightforward: when sleep pressure is greater than arousal, we fall asleep; when arousal is higher, we remain awake. Let’s dive deeper into these concepts to discover practical strategies to improve sleep hygiene.

Sleep Pressure

Sleep pressure is your body's drive to sleep and it is influenced by the following factors:

·       Circadian Rhythm is your internal body clock, a 24-hour cycle that regulates sleep and wakefulness. Keeping a regular sleep schedule can help maintain this rhythm. For shift workers or those with irregular schedules circadian rhythm can become impacted.

·       Adenosine is a chemical that builds up in your brain while you’re awake, making you feel increasingly tired. When asleep, our brain and body consume this adenosine. Exercise boosts adenosine levels, which helps increase sleep pressure. However, napping can reduce your adenosine levels, making it harder to sleep at night.

·       Melatonin is a hormone that the body produces naturally to regulate the timing of sleep, but it doesn’t directly induce sleep. You can think of melatonin as the starting pistol in a race, signalling that it’s time to start preparing for sleep. It is released from a part of the brain that monitors light levels, when light decreases, melatonin production increases. However, if you’re in a bright artificial environment at night, your brain doesn’t receive the message that it’s time to prepare for sleep, which can delay sleep onset.

·       Chronotype refers to an individual's natural preference for being active during certain times of the day. It influences when a person feels most alert and when they prefer to sleep. Common chronotypes include "morning people" (larks), who feel most awake in the early hours, and "evening people" (owls), who thrive later in the day. Understanding your chronotype can help optimise sleep schedules and improve overall well-being by aligning activities with your body’s natural rhythms.

·       Your brain learns to associate certain environments and behaviours with sleep called sleep associations. The strength of sleep associations depends on how well we maintain them purely for sleep. For example, if we sit in our bed and watch TV that dilutes our sleep association with our bed and increases the expectation of watching TV instead.

Strategies to increase sleep pressure include:

·       Improve the regularity of your circadian rhythm through a consistent sleep schedule with regular sleep and wake times

·       Increase adenosine by avoiding daytime naps and engaging in regular exercise

·       Signal your brains melatonin production by reducing light exposure of an evening (turn off big lights, use warm lighting such as lamps and candles) and increase morning light exposure to set your wake drive for the day

·       Build strong sleep associations by using your bed solely for sleep (and intimacy) and wearing your pyjamas only at night time

Arousal

Arousal can stem from stress, anxiety, environmental factors, or stimulants. A high level of arousal can make it more challenging to fall asleep, as you will need greater sleep pressure to overcome this. Key influences of arousal include:

·       Caffeine has a two-fold impact on your brain. It is both a stimulant which increases your arousal and an adenosine blocker which reduces sleep pressure.

·       Alcohol has an interesting impact on sleep. As a depressant some people may initially find that alcohol relaxes them making it easier to fall asleep. However, alcohol has got what is known as a “half life” which means it becomes a stimulant a few hours after ingestion and has been shown to disrupt your sleep cycle and block deep sleep which can leave you feeling unrefreshed.

·       Certain foods such as sugar, which is a stimulant, can increase your arousal before bed.

·       Stress, worry and anxiety also arouses your brain functioning and can impede your ability to both fall and stay asleep.

·       Other environmental factors can also serve to increase arousal such as a noisy neighbour, snoring partner or barking dog. The temperature in your room can also impact upon your sleep. We tend to prefer a cooler temperature for sleep, and this is due to our bodies core temperature dropping as we enter deep sleep.

Strategies to decrease arousal before bed include:

·       Limit caffeine and sugar intake later in the day

·       Avoid alcohol before bed

·       Engage in mindfulness and relaxation prior to bedtime

·       Our brains have a tendency to focus on stressful and anxiety provoking situations of an evening when the distractions of the world around us are reduced.  Consider the use of journaling an hour before bed to work through any stress and anxiety. 

·       Keep your bedroom on the cooler side. Consider having a warm shower prior to bed which will raise your body temperature temporarily. When you step out, your body begins to cool down, mimicking the natural drop in core body temperature that occurs when you fall asleep. This cooling process can signal to your body that it’s time to sleep.

References

A lot of this info comes from a couple of really fantastic YouTube videos done by the PsychCollective a few years ago. Links are:

·       https://www.youtube.com/watch?v=1zDTI4hH5vY&t=4s

·       https://www.youtube.com/watch?v=AqwEXMk4ddM

I have done my own research to check the information and found these articles to back up the science

Basheer, R., Strecker, R. E., Thakkar, M. M., & McCarley, R. W. (2004). Adenosine and sleep–wake regulation. Progress in neurobiology, 73(6), 379-396. https://doi/org/10.1016/j.pneurobio.2004.06.004

Dworak, M., Diel, P., Voss, S., Hollmann, W., & Strüder, H. K. (2007). Intense exercise increases adenosine concentrations in rat brain: implications for a homeostatic sleep drive. Neuroscience, 150(4), 789-795. https://doi/org/10.1016/j.neuroscience.2007.09.062

Harding, E. C., Franks, N. P., & Wisden, W. (2019). The temperature dependence of sleep. Frontiers in neuroscience, 13, 336. https://doi/org/10.3389/fnins.2019.00336

Ruan, W., Yuan, X., & Eltzschig, H. K. (2021). Circadian rhythm as a therapeutic target. Nature Reviews Drug Discovery, 20(4), 287-307. https://doi/org/10.1038/s41573-020-00109-w

Thakkar, M. M., Sharma, R., & Sahota, P. (2015). Alcohol disrupts sleep homeostasis. Alcohol, 49(4), 299-310.https://doi/org/10.1016/j.alcohol.2014.07.019