What are the effects of sleep deprivation on the skin?

The aforementioned study also evaluated the impact of sleep deprivation on skin hydration, desquamation, and transepidermal water loss (TEWL). The researchers found that skin hydration significantly decreased after the first night and continued to decrease progressively. Skin desquamation significantly increased after a night of reduced sleep, and continued to increase throughout the period. Finally, the TEWL was higher than the value for normal sleep (eight hours of sleep per day) by the sixth day, increasing from 16 g/m2h to 19 g/m2h. The skin then becomes less hydrated, and drier.

The circadian rhythm, or theinternal clock synchronized with the light-dark cycle of the environment, orchestrates numerous cellular functions. Sleep promotes a microenvironment conducive to cell proliferation, migration, and differentiation. These effects are mediated either directly by the genes of the circadian clock (CLOCK), or indirectly by hormones, such as melatonin and cortisol. Thus, not getting enough sleep leads to poor cell regeneration and therefore an accumulation of dead cells on the skin's surface. This consequence may be linked to the observed skin dryness, in parallel with the increased Transepidermal Water Loss (TEWL).

Furthermore, recent studies have revealed that circadian rhythms would affect the metabolism of skin lipids, produce different lipid products, and in turn affect the TEWL (Transepidermal Water Loss). However, the exact mechanisms are not yet known.

When we don't get enough sleep, our complexion tends to turn a bit grayish, as shown in a study conducted by Damien LEGER and his team in 2019 (three hours of sleep per night for two consecutive nights). Changes in skin tone are widely perceived as a symptom of sleep deprivation. This change is particularly noticeable under the eyes with the dark circles.

In an experiment conducted by Hae-Kwang LEE, it was observed that skin blood circulation decreased after a night of sleep deprivation, alongside a more significant presence of dark circles. Indeed, the stagnation of blood flow contributes to the development of under-eye circles. The blood pigments that show through the thin skin are responsible for the dark color of the circles. The blood capillaries are filled with blood and dilate, releasing the pigmented waste into the perivascular space. Similarly, the lymph, responsible for waste removal, has difficulty circulating and therefore cannot eliminate the accumulated pigments.

Our complexion can also turn yellowish due to lack of sleep. Tomohiro HAKOZAKI and his team measured the effects of total sleep deprivation (0h) and repeated partial sleep deprivation, which is four hours of sleep for five consecutive nights, on the dullness of facial skin. They then examined yellow chromophores, such as bilirubin and carotenoids, in the blood serum as potential causes of the yellowing. Both protocols significantly worsened the yellowing of the facial skin. However, the absence of significant changes in circulating levels of yellow chromophores suggests that the increase in yellowing is likely regulated by epidermal keratinocytes, which are capable of producing substantial amounts of bilirubin.

Recurring insomnia can lead to the onset of skin diseases. In an experiment conducted in 2019, Elma D. BARON and her colleagues sought to determine if there was a significant difference in the prevalence and severity of skin diseases between day workers and night workers. Due to their disrupted circadian rhythm, the latter were much more affected by skin conditions such as common acne and dermatitis, as well as enlarged pores.

Lack of sleep leads to an increase in the production of glucocorticoids, which can impair the integrity of lamellar bodies and thus the integrity of the skin through a modification of the conformation of collagen molecules. Additionally, as previously mentioned, sleep deprivation results in an increase in pro-inflammatory cytokines, such as TNF-α, which promote cell differentiation, oncogenesis, and the pathogenesis of inflammatory skin conditions like psoriasis. Reactive oxygen species (ROS) will also be produced. In excess, these oxidants can react with all cellular macromolecules, including lipids, proteins, nucleic acids, and polyunsaturated fatty acids of cell membranes. This triggers a chain reaction, leading to cellular damage.

It's important to understand that ROS (Reactive Oxygen Species) can also increase the levels of pro-inflammatory cytokines by upregulating the genes that encode them.

Furthermore, lack of sleep results in a dysregulation of the immune system. It has been observed that the number of leukocytes reaches its peak during the night, such as T lymphocytes controlled by a direct activation of the IL-23 promoter by the circadian rhythm of the CLOCK protein. A lack of sleep then leads to a decrease in immune cells and thus an exposure to infections.