Sleep, often the cornerstone of good health, is profoundly influenced by a complex interplay of hormones and biological rhythms. Among them, cortisol, often called the stress hormone, plays an important but underappreciated role.

Secreted by the adrenal glands, cortisol follows a precise 24-hour cycle, adapting to our biological rhythms to regulate wakefulness, alertness, and relaxation.

However, when this rhythm is disrupted – whether due to lifestyle factors, stress or sleep disorders – the consequences affect every aspect of our physical and mental well-being.

Experts explain the complex relationship between cortisol, the stress hormone, and sleep.

The Cortisol Clock: A 24-Hour Cycle

Cortisol follows a daily rhythm, peaking in the morning around 8 a.m. It begins to rise during the second half of sleep, helping to stimulate wakefulness as you drift off to sleep. Throughout the day, cortisol levels gradually decline, reaching their lowest point near midnight, coinciding with the natural urge to sleep.

This rhythm is a cornerstone of sleep health, ensuring you stay alert during the day and relaxed enough for restorative sleep at night. Disruption of this rhythm, such as from stress or lifestyle factors, can significantly impact the quality of your sleep.

The HPA axis and its impact on sleep

Cortisol production is regulated by the hypothalamic-pituitary-adrenal (HPA) axis, which operates at low levels during the evening to prepare the body for sleep. However, disturbances in the HPA axis—whether due to stress, clinical sleep disorders such as obstructive sleep apnea (OSA), or poor sleep habits—can alter this balance.

Cortisol overload: Lack of sleep leads to high cortisol levels, which not only impair sleep habits but also result in wider health problems.

According to experts, chronic insomnia and hyperactivation of the HPA axis are linked to obesity and type II diabetes. Elevated cortisol levels may interfere with glucose metabolism and insulin sensitivity, contributing to these conditions.

To optimize cortisol rhythms and promote restful sleep:

Keep a fixed sleep schedule, go to bed and wake up at the same time every day.

Create a quiet environment in the evening to naturally reduce cortisol levels, such as turning off the lights and avoiding the phone.

Engage in stress management techniques such as yoga, meditation, or breathing exercises.

Avoid caffeine and high-calorie meals before bedtime.