We all know that a good night’s sleep is important for our health and wellbeing. But sometimes, despite our best efforts, sleep just doesn’t come easily. One of the main culprits behind poor sleep is high cortisol levels.
Cortisol is our primary stress hormone. It is released by the adrenal glands as part of the body’s natural response to stress, as mediated by the hypothalamic-pituitary-adrenal (HPA) axis. Acute stress causes a spike in cortisol which helps give us the energy boost we need to deal with threats and challenges. However, when we experience chronic stress and cortisol remains elevated over long periods, it can start to cause problems.
One of the key issues is that high cortisol at night disrupts and inhibits deep, restorative sleep. Here’s a look at some of the main ways elevated cortisol hampers our ability to sleep soundly:
Increases Nighttime Awakenings
Cortisol helps make us more alert and primes our body for action. Having high cortisol levels at night therefore makes it much easier for minor noises or disturbances to fully wake us up. We may find ourselves frequently stirring, having difficulty going back to sleep after nighttime awakenings. High cortisol creates a hypervigilant state not conducive to restful slumber.
Disrupts Circadian Rhythms
Our natural circadian rhythms regulate our sleep-wake cycles and other important bodily processes tied to the 24-hour day. Cortisol normally follows a daily pattern, peaking in the morning to energize us for the day, and declining in the evening to allow sleep. But chronic stress can dysregregate this cycle and cause abnormally high nighttime cortisol. This confuses our endogenous circadian clocks and makes it harder for our bodies to relax and prepare for sleep.
Increases Rapid Eye Movement (REM) Sleep
REM sleep is when we experience vivid dreams and is important for cognitive function and memory consolidation. However, too much REM sleep can leave us feeling unrested upon waking. Studies show elevated cortisol is linked to increased percentages of REM sleep. This prevents us from spending enough time in restorative slow-wave NREM sleep stages. The end result is more restless, fragmented sleep.
Impacts Melatonin Secretion
The hormone melatonin is our body’s natural sleep regulator. It builds up in the evening and makes us feel drowsy, while being suppressed in the morning to wake us up. But cortisol can inhibit the release of melatonin at night. When cortisol is high, it essentially overpowers the sleep-inducing effects of melatonin. This makes it very difficult for our brains and bodies to relax and transition into sleep mode.
Increases Nighttime Anxiety
Cortisol stimulates activity in the amygdala, the emotional center of the brain governing fear and anxiety. Being stressed out and worrying at night activates the HPA axis, further increasing cortisol release. This anxiety and rumination makes it incredibly tough to fall asleep. The mind races with stressful thoughts rather than settling down for rest. It becomes a vicious cycle – anxiety boosts cortisol and cortisol exacerbates anxiety.
Causes Metabolic Issues
Besides psychological and circadian effects, high cortisol also induces metabolic changes antithetical to sleep. Cortisol raises blood sugar levels, as it helps mobilize energy stores. But elevated glucose at night can make it harder to fall and stay asleep. High cortisol also stimulates insulin production, which can cause reactive hypoglycemia. Nighttime blood sugar crashes lead to release of adrenaline, making us wired and jittery rather than sleepy.
Increases Frequency of Nighttime Bathroom Trips
Cortisol acts as a diuretic, increasing urine output to keep the body hydrated and prime the muscles for fight-or-flight responses. But the downside is needing to make more frequent nightly trips to the bathroom, interrupting sleep. Waking up to urinate multiple times makes it challenging to sink into deep, uninterrupted sleep cycles throughout the night.
Triggers Low Blood Pressure
Studies show elevated cortisol correlates with lower nighttime blood pressure. This may be due to increased nitric oxide levels relaxing blood vessels. While lower blood pressure helps rest the heart, it can also cause headaches, dizziness, faintness and fatigue. These symptoms disrupt sleep and can cause insomnia at night along with tiredness the next day.
So in summary, sustained high cortisol has diverse detrimental effects on multiple aspects of normal sleep architecture and circadian biology. It inhibits our body’s natural transition into deeper hypometabolic sleep states. The end result is sleep that is lighter, more fragmented, and less restorative.
If you are struggling with poor sleep, evaluating and addressing high cortisol may be an important piece of the puzzle. Here are some tips for lowering nighttime cortisol and improving sleep quality:
- Have a consistent relaxing bedtime routine to prepare your body for sleep
- Avoid stimulating screens and bright lights before bedtime
- Manage stress and anxiety using techniques like meditation, yoga, deep breathing
- Exercise during the day to metabolize cortisol; avoid exercise near bedtime
- Follow a low-glycemic diet to prevent blood sugar highs and crashes
- Supplement with magnesium, ascorbic acid, phosphatidylserine which help lower cortisol
- Consider adaptogens like ashwagandha, Rhodiola rosea and Relora which help regulate the HPA axis
- Optimize sleep conditions by keeping your bedroom cool, dark and quiet
- Go to bed and wake up at consistent times to stabilize circadian rhythms
- Limit caffeine, alcohol and high-sugar foods which can disrupt sleep-wake cycles
Getting your cortisol levels under control and optimizing your sleep health takes time and consistency. But it is one of the best things you can do for your overall health, wellbeing and cognitive performance. Give some of these cortisol-lowering tips a try to take back your sleep from high stress hormone levels.