How sleep affects cortisol and how cortisol affects sleep.

The Importance of Sleep

It's 10pm and you're ready for bed. You've been tired all day and are soooo ready to get some sleep. You lay down and put your head on the pillow and . . . . nothing. You're thinking through the day, about the day tomorrow, about the imaginary conversation you need to have with your boss, if your letting your kids watch too much Paw Patrol. You feel this surge of energy and just can't sleep. Finally you drift off around 1am or 2 only to wake up again at 4am and then, just as you are drifting off... in comes the toddler demanding you take off her pull-up and that it's time to wake up. 

Sound familiar?

You're not alone! Sleep issues plague so many of us. While there are a number of different reasons for not getting a good night's sleep, today we are going to talk about sleep and stress.

Sleep and stress go hand in hand.

Poor sleep has been linked with negative health outcomes (Hackett, Dal, & Steptoe, 2020).  Studies have shown that adults who report sleep problems are more likely to have:

• hypertension
• obesity
• heart disease
• metabolic syndrome
• blood sugar imbalance

With the concept of allostatic load, sleep problems are thought to contribute over time to wear and tear on the body, resulting in disturbance across multiple biological systems including the HPA axis (Hackett, Dal, & Steptoe, 2020).  

Sleep is essential to our health and wellbeing. It is one of the most important lifestyle factors to work on. Sleep helps with:

• Cortisol Rhythm Restoration: Quality sleep helps restore the diurnal cortisol rhythm. With adequate sleep, cortisol levels are highest in the morning, providing the necessary energy for the day, and decrease as the day progresses, promoting relaxation in the evening.
• Stress Resilience: A well-rested body is more resilient to stress. When cortisol levels are properly regulated, the body can respond to stressors more effectively and recover faster.
• Emotional Well-being: Quality sleep is essential for emotional regulation and mental health. It allows the brain to process and manage emotions, reducing the risk of anxiety and depression.
• Cognitive Function: Adequate sleep is crucial for cognitive functions like memory, problem-solving, and decision-making. Uninterrupted sleep allows for the consolidation of memories and learning.
• Physical Health: Proper sleep supports the body's natural ability to heal, repair, and maintain overall physical health. This includes a strong immune system, cardiovascular health, and metabolic regulation.
• Weight Management: Quality sleep can help manage body weight by reducing cortisol-driven weight gain. It supports healthy metabolic functioning and appetite regulation.

How cortisol affects sleep

Cortisol, one of the primary stress hormones , is intricately linked with our sleep/wake cycles. The HPA axis releases cortisol in a diurnal pattern. This is where circulating concentrations peak at usual sleep-wake transition and gradually decrease during the late evening/early night. This rhythm is driven by the central circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus (O’Byrne, Yuen, Butt, & Liu, 2021). Neural signaling from the suprachiasmatic nucleus is also mediated hormonally by the adrenal axis . . . and therefore cortisol.  

Optimal sleep is associated with a healthy diurnal pattern of cortisol release (Hackett, Dal, & Steptoe, 2020). Ideally, there is a brief peak in cortisol in the morning 30-45 minutes after awakening (Cortisol Awakening Response) and there is a gradual decline over the day (Nys, Anderson, Ofosu, Ryde, Connelly, & Whittaker, 2022). When you look a cortisol curve, a sharper decline is associated with  better physical and mental health (Nys, Anderson, Ofosu, Ryde, Connelly, & Whittaker, 2022). If your diurnal pattern is off and cortisol is released differently, it can leave you feeling "tired but wired". This insomnia is one of the most common feelings people report when they have a cortisol imbalance. 

The literature is a bit mixed when it comes to links between specific cortisol patterns and poor sleep. Studies have shown both an increase and decrease in morning cortisol concentrations are associated with poor sleep (Hackett, Dal, & Steptoe, 2020). Others have shown that a flatter cortisol curve throughout the day, or both raised and low evening cortisol levels are present in those with sleep problems (Hackett, Dal, & Steptoe, 2020).  

The above image is a copy of my cortisol curve a year ago. You can see that there is a slow gradual rise over the day with a peak in the afternoon. Not ideal, but now you know that I'm practicing what I preach because it's worked for me and I know it will work for you too! 

How sleep affects cortisol

While cortisol can affect your ability to sleep, sleep itself affects cortisol. Poor sleep can impact the reactivity of the HPA axis to stress (Hackett, Dal, & Steptoe, 2020).

Quality sleep is a natural, potent regulator of cortisol levels. When we sleep, our bodies go through various sleep cycles, including rapid eye movement (REM) and non-REM stages. It is during these cycles that important physiological processes occur, including cortisol regulation.

• Cortisol Regulation during Sleep Cycles:
• Non-REM Stages: During non-REM sleep, cortisol levels drop significantly. This allows the body to recover, repair tissues, and restore energy.
• REM Sleep: Interestingly, during REM sleep, cortisol levels increase slightly, possibly playing a role in memory consolidation and emotional processing. However, the overall trend during a full night's sleep is a decrease in cortisol levels.
• The Importance of Deep Sleep:
• Deep, slow-wave sleep is crucial for cortisol regulation. This is the stage of sleep where cortisol levels are at their lowest, and the body can engage in deep restoration and repair. 

One thing to note is the idea of chronotypes - early bird or night owl - this is related to a variation in the SCN clock genes. Our genetics do determine if we are an early bird or a night owl, but this has no effect on the cortisol awakening response. If you can help it, don’t force yourself to be something you are not! A morning routine can happen at any time of day and you still need to shoot for 8 hours of sleep whether you go to bed at 8:30pm (hi! it's me!) or 1:00am. Figure out ways to adjust to what feels right for you. 

Tips for getting a good night sleep

Sleep hygiene has been shown to impact cortisol levels through a decreased activation of the HPA axis. On the flip-side, sleep disruption increases activation of the HPA axis leading to increased stress and continuing the cycle of stress-poor sleep- more stress. 

Here are 10 key tips for getting a good nights sleep:

1. Have a consistent sleep schedule. Go to bed and wake up at the same time everyday, even on the weekends. 
2. Create a comfortable sleep environment. Keep your bedroom dark, cool and quiet (or use white/pink noise).
3. Limit screen time before bed. The blue light from phones and computers can interfere with your sleep. Turn off screens at least an hour before to help your brain start to wind down. 
4. Avoid stimulants. Limit caffeine and alcohol intake in the hours leading up to bedtime
5. Practice relaxation. Try a few moments of meditation, deep breathing or progressive muscle relaxation to help lower stress and prepare the body for sleep. Need help? Grab a copy of my free stress busting guide to learn how to do the 4-7-8 breath to wind down. CLICK HERE.
6. Regular exercise. Getting in some movement throughout your day can improve the quality of your sleep. It's best to do your more vigorous exercise earlier in the day rather than close to bedtime. 
7. Eat like a pauper. The old saying "eat breakfast like a king, lunch like a prince, and dinner like a pauper" has some relevance! Heavy meals before bedtime can disrupt sleep. You want to have some space between dinner and bed so your body isn't trying to digest while you're sleeping. 
8. Limit naps. Naps can be wonderous, but don't nap more than 90 minutes. Napping too long can disrupt your nighttime sleep. 
9. Have a routine. Routines help our body know what is getting ready to happen and can prepare our minds for sleep. Just like toddlers, having a nighttime routine can get you off to sleep faster. 
10. . Have a hot bath 1-2 hours before bedtime can be useful, as it will raise your body temperature, causing you to feel sleepy as your body temperature drops again. Research shows that sleepiness is associated with a drop in body temperature (that's also why having a cool room to sleep in is key!)

Key take aways

Sleep is essential for stress management and balanced cortisol levels, but cortisol also plays a roll in how well we sleep. It's a feedback loop that sometimes gets out of control. Poor sleep has been linked to a number of health issues that are also tied to cortisol imbalance and chronic inflammation. Getting a good nights sleep is one master key to your health. Working on sleep hygiene can help you develop good sleep habits and correct some of the imbalances you are feeling. If you consistently incorporate sleep hygiene practices in your day and still have trouble sleeping, make sure to work with your PCP or GP to identify other issues that might be at play, e.g. sleep apnea. If you're taking medications, talk with your provider to make sure you're taking them at the right time as some medications have stimulating effects. 

References

Hackett RA, Dal Z, Steptoe A. The relationship between sleep problems and cortisol in people with type 2 diabetes. Psychoneuroendocrinology. 2020 Jul;117:104688. doi: 10.1016/j.psyneuen.2020.104688. Epub 2020 Apr 23. PMID: 32353817; PMCID: PMC7302424.

O'Byrne NA, Yuen F, Butt WZ, Liu PY. Sleep and Circadian Regulation of Cortisol: A Short Review. Curr Opin Endocr Metab Res. 2021 Jun;18:178-186. doi: 10.1016/j.coemr.2021.03.011. Epub 2021 May 5. PMID: 35128146; PMCID: PMC8813037.

Nollet M, Wisden W, Franks NP. Sleep deprivation and stress: a reciprocal relationship. Interface Focus. 2020 Jun 6;10(3):20190092. doi: 10.1098/rsfs.2019.0092. Epub 2020 Apr 17. PMID: 32382403; PMCID: PMC7202382.

Nys, LD, Anderson, K, Ofosu, EF, Ryde, GC, Connelly, J, Whittaker, AC. The effects of physical activity on cortisol and sleep: A systematic review and meta-analysis. (2022) Psychoneuroendocrinology 143. DOI: 10.1016/j.psychoneuen.2022.105843