Blue light effect and ethnicity - in shadow of skin pigmentation and eye colour

Abstract

Introduction. Blue light [wavelength between 400-495nm], from digital sources and artificial lighting in the evening, hence inhibit normal secretion patterns of melatonin causing circadian rhythm and sleep disturbances. There is an inversely proportional relationship between blue light exposure and melatonin secretion. In the same time, blue light can be absorbed by the pigmental layer of the retina that contains melanin. Thereby, the quantity of blue light that will rich the retina can be influenced by the amount of melanin from the eyes. Aim of the study. The purpose is to appreciate the circadian rhythm and sleep disturbances and depth of blue light effect on melatonin secretion on different ethnical groups, integrating skin and eye pigmentation effects on the same matter; Materials and methods. An analysis of the latest scientific sources has been carried out using the PubMed search engines, 'HINARI' and Google Academic with the help of keywords: blue light, ethnicity, skin pigmentation and eye colour, sleep quality, sleep consistency, sleep duration. Results. The role of ethnicity in most aspects of human health is well documented. An example is the inefficiency of certain drugs used in asthma treatment in certain racial groups. Other studies determined a decrease in prevalence and incidence of Parkinson Disease in Americans of African descent compared to Caucasians. Also, shorter sleep was reported in black than in Asian, in Asian than in Hispanic/Latin and in Hispanic/Latin than in White. More sleep quality disturbance was reported in Black than in Asian and in Asian than in Latin. One of the explanations of the influence of ethnicity on sleep is the amount of melanin in the eyes. Some studies have shown that physiological responses to light depend on eye colour and that intraocular light scattering is higher in blue-eyed Caucasians. The percentage of suppression of melatonin secretion two hours after the start of light exposure was significantly more abundant in light-eyed Caucasians than in dark-eyed Asians. In the same time, in a comparative study which analysed the influence of light treatment in Seasonal Affective Disorder (SAD), was found that following six weeks of light therapy, African-American participants with SAD had a lower remission rate than Caucasian participants. Researchers suggested that higher melanin content of the pupil and retinal pigment epithelium in African-Americans may reduce the retinal illuminance in African-American SAD patients during light treatment hence reducing the effect of light therapy. These results suggest that the sensitivity of melatonin to light suppression is influenced by eye pigmentation and can be related to ethnicity, respectively.