Lack of sleep: a possible cause of dull complexion?

According to the National Institute of Sleep and Vigilance, adults on average require 7 to 9 hours of sleep per night to be in good shape and carry out their daily activities. However, according to a study by Inserm, the French on average sleep 6 hours and 42 minutes on weekdays and have lost approximately 1 hour and 30 minutes of sleep over the past fifty years. In the short and long term, this sleep deprivation can have harmful effects on the functioning of the body and brain. This can notably increase the risk of cardiovascular diseases, lower immune defences and impair psychological functions. The lack of sleep can also reflect on the skin, in various ways.

Several studies show that a lack of sleep can harm the uniformity of the complexion.

When we don't get enough sleep, our complexion tends to turn gray. This change is most noticeable around the eyes, with dark circles, but is also reflected throughout the face. Several studies have shown that skin blood circulation decreases after a poor night's sleep, while dark circles increase and the complexion loses its radiance. Indeed, the stagnation of blood flow contributes to the dulling of the complexion and the appearance of dark circles. The blood pigments that show through the thin skin of the eye contour are responsible for the dark colour of the circles. When blood circulation slows down, the blood capillaries, filled with blood, dilate and release the pigments into the perivascular space. In parallel, the lymph, responsible for removing waste, struggles to circulate and therefore cannot eliminate the accumulated pigments, resulting in a yellowing of the complexion.

The effects of sleep deprivation on complexion were recently highlighted in a study conducted by HAKOZAKI and his team. Two experiments were carried out: a first group of 10 volunteers underwent total sleep deprivation for one night, while a second group of 28 participants only slept four hours for five consecutive nights. The researchers observed that these two protocols significantly increased the yellowing of the skin on the volunteers' faces. However, the circulating levels of carotenoids and bilirubin, yellow pigments present in the body, were not altered. Furthermore, no significant alteration in the blood levels of biopyrrin, a biomarker of oxidative stress, was noted. The following hypothesis was then put forward: the yellowing of the complexion observed following sleep deprivation could be regulated by epidermal keratinocytes, capable of producing bilirubin in situ.

The dulling of the complexion due to lack of sleep could also be explained by a poor cell regeneration. Indeed, the circadian rhythm, that is the internal clock linked to the day-night cycle and surrounding light, impacts numerous cellular functions. This is done through the circadian clock genes, known as CLOCK, which notably regulate the release of hormones such as melatonin and cortisol. It has been shown that cell migration and differentiation reach a peak during the night, under the influence of these hormones. Therefore, not sleeping enough can harm cell regeneration and promote the accumulation of dead cells on the skin's surface. This causes a thickening of the horny layer, which is then no longer able to correctly reflect light, giving the skin a greyish and dull appearance.