Cortisol and Sleep

Sleep Quality Impaired by Increased Cortisol Levels.

The adrenal glands are situated on top of the kidneys, the particular segment of the adrenals of interest here is the adrenal cortex where the synthesis of cortisol from cholesterol takes place.This is a vital hormone that is often referred to as the "stress hormone" as it is involved in the response to stress.

Cortisol regulation during the sleep wake cycle 

The amount of cortisol present in the serum undergoes diurnal variation, with the highest levels present in the early morning, and the lowest levels present around midnight, 3-5 hours after the onset of sleep.This applies to those individuals who have regular sleep wake cycles. The secretion of cortisol is regulated primarily by the hypothalamus and anterior pituitary gland. Information about the light/dark cycle is transmitted from the retina to the paired suprachiasmatic nuclei in the hypothalamus, see diagram below.

Suprachiasmatic Nuclei

Stress and Serum Cortisol Levels:

 Serum cortisol levels have been observed to fluctuate in connection with abnormal ACTH levels, clinical depression, psychological stress, and such physiological stressors as hypoglycemia, illness, fever, trauma, surgery, fear, pain, physical exertion or extremes of temperature. Cortisol secretion appears to be an important requirement for mounting a response to stress.

 Coping with stress is a necessary part of modern day living, since it's almost impossible to avoid stress, it is of paramount importance to control the reactions to stress and so maintain healthy levels of serum cortisol. High levels of cortisol result in hyperglycemia, this is fine if the individual has to cope with an emergency, for the extra glucose provides a ready source of energy. However, prolonged stress may cause hyperosmolality resulting in disturbed electrolyte balance and brain function.

Increased cortisol secretion from prolonged severe stress can suppress the immune system which may lead to tissue destruction, and the initiation of an autoimmune reaction.It lowers bone formation thus favoring development of osteoporosis in the long term. Prolonged exposure to cortisol causes damage to cells in the hypocampus resulting in impaired learning. Excess cortisol decreases protein synthesis, increases protein degradation leading to muscle wasting, and interfers with skin regeneration and wound healing.

How to avoid high cortisol levels during sleep:

Both the quality and quantitiy of sleep  determine cortisol levels, researchers have found that  impaired sleep results in increased cortisol levels, and decreased levels in growth hormone. The drop in growth hormone is associated with an increase of fatty tissue, weakened immunity, and a decline in general health. As people age sleep quality and quantity is diminished, and cortisol levels increase, this results in a compromised immune system which may be the cause of many diseases associated with aging, including impaired memory.

Following a healthy diet, eating a small protein carbohydrate combination snack before bedtime, some form of moderate exercise at least 1 hour before bed, and excluding any form of caffeine after midday. Over indulgence in coffee can contribute to high cortisol levels. 

Read more: REM Sleep