Cortisol peak at night is normal

Waking up at night around three o'clock does not necessarily indicate a sleep disorder. This is because the body releases its highest level of cortisol, a hormone linked to wakefulness, at this time, which coincides with lighter sleep stages.

Study identifies cortisol timing

In November 2022, researchers from the Oregon Health and Science University identified the exact moment when cortisol rises in the body, according to a study published in Frontiers in Neuroscience. Their method involved shifting the internal clock of volunteers day by day to separate the effects of sleep from the circadian rhythm, a rare approach in laboratory settings.

Forced desynchronization method

The researchers measured this hormonal peak in 34 adults, including 20 women, using a protocol known as forced desynchronization. Participants' bedtime schedules changed each day by a few hours, and salivary melatonin levels were continuously collected to track each person's internal cycle.

Cortisol peak occurs at specific time

The teams measured cortisol levels from the moment of waking, regardless of the time. The hormonal response peaks around 3:40 a.m. in internal time. This peak fades by the end of the afternoon and the beginning of the evening. It becomes more pronounced when waking occurs approximately three hours earlier than usual.

Sleep patterns and hormonal changes

Sleep does not flow uniformly, and this hormonal rise occurs at the worst possible time. The study shows that the cortisol peak is part of the body's natural rhythm and is not simply due to accumulated fatigue.