Sleep
How does light influence sleep?
Article written by Rut Ruiz, scientific editor at AdSalutem Instituto del sueño, a partner of the BBHI in the field of sleep.
Sun exposure is essential for quality sleep and to protect our health. It is the main environmental signal for regulating our circadian rhythms, allowing us to synchronise our biological clock with the daily and seasonal light-dark cycle. So it is just as important to receive sufficient light during the day as it is to receive darkness at night.
Most physiological processes are influenced by these circadian oscillations: temperature control, blood pressure, hormone regulation; or some of our behaviours (when to sleep or wake up, when to exercise, eat or be more productive and creative). Circadian dysfunctions are implicated in some of the most common sleep disorders, for example, jet lag or phase delay, characterised by a later sleep schedule.
The quality of sleep depends directly on how synchronised our clock is with the light-dark cycle, as well as the nuances of colour, intensity and timing of light exposure.
Waking up to bright light at the start of the day is beneficial for activation and subsequent sleep quality. In this respect, the recent change to winter time helps us to coincide the start of our activity with sunrise.
However, exposure to bright, intense blue light from screens late in the day is detrimental to sleep. It is no coincidence that evening light is warm, orange and less intense, as it signals that we should prepare for sleep. Darkness is the signal for the synthesis of melatonin - a hormone involved in the sleep process - which serves as a messenger of darkness to the rest of the body. Conversely, cortisol, the hormone that allows us to be alert, is at its lowest levels when darkness arrives, and highest shortly after waking up.