Suppression of Nocturnal Plasma Melatonin and 6-Sulphatoxymelatonin by Bright and Dim Light in Man

Abstract

Previous studies have shown that bright light (2500 lux) suppresses nocturnal secretion of melatonin, while dim light (500 lux) has little or no effect. We have studied the effect of varying intensities of light on 5 normal male volunteers (age 18-28). The experiment was divided into 3 parts which took place at weekly intervals. Subjects remained under artificial light (fluorescent strip 150-250 lux) between 2000 h-2300 h, they then retired to bed in darkness. On each occasion, between 0030 h and 0100 h, the subjects were required to get up and were treated with light of different intensities; (a) less than 1 lux, (b) 300 lux and (c) 2500 lux respectively. Subjects returned to bed in darkness until 0700 h. Blood was sampled hourly from 2000 h-1000 h with additional samples at 2330 h, 0015 h, 0030 h, 0045 h, 0115 h and 0130 h. Plasma melatonin and 6-sulphatoxymelatonin (aMT6s), the major melatonin metabolite, were measured by radioimmunoassay. Dim (300 lux) and bright (2500 lux) light, both significantly suppressed melatonin levels compared to less than 1 lux (P less than 0.05 and P less than 0.01 respectively) at the following time points 0100 h, 0115 h and 0130 h. One subject did not show suppression with 300 lux. There was also a significant suppression of aMT6s levels, compared to less than 1 lux, after both 300 lux and 2500 lux at 0115 h (P less than 0.05, P less than 0.01), 0130 h (P less than 0.01, P less than 0.01) and 0200 h (P less than 0.01, P less than 0.001) respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Melatonin Sensitivity to Dim White Light in Affective Disorders

“…More recent studies have investigated the relationship between light intensity and melatonin suppression. Whilst some researchers have reported no differences in melatonin response to varying light intensities (1000 lux and 2500 lux) (Boyce and Kennaway 1987), more recent reports have suggested that humans are sensitive to lower levels of light (300 lux) (Bojkowski et al 1987). McIntyre et al (1989a) also reported a response to low levels of light and suggested an intensity dependent relationship between light and percentage of nocturnal melatonin suppression (3000, 1000, 500, 350, and 200 lux), with no gender differences (Nathan et al unpublished observations).…”

Auditory and Visual Evoked Potentials as a Function of Sleep Deprivation and Irregular Sleep

“…Our data suggest that ambient light intensity may also be a factor masking the endogenous rhythm in humans. Although the intensity of light found here to affect temperature was high, others have reported behavioral and physiological effects with much lower levels (e.g., Bojkowski et al, 1987;Boyce & Kennaway, 1987;Czeiler et al, 1989;McIntyre et al, 1989;Moore-Ede, Sulzman, Fuller, 1982;Sulzman, Fuller, & Moore-Ede, 1979). Thus, a prudent approach suggests that ambient light intensity be considered another possible factor 153 masking the endogenous temperature rhythm.…”

“…Specifically we asked "Will nighttime exposure to light intensities sufficient to suppress melatonin synthesis reduce sleepiness and enhance nighttime alertness and performance levels during sustained wakefulness?" We should note at the outset that we did not assay melatonin levels but, instead, used a light intensity found repeatedly to suppress nighttime melatonin to near daytime levels (Bojkowski, et al, 1987;Lewy et al, 1980;McIntrye et al, 1989). A second question relates to nighttime body temperature.…”

Intense blue light therapy during the night-time does not suppress the rhythmic melatonin biosynthesis in a young boy

“…Its production is under the circadian control of the master circadian oscillator localized in the hypothalamic suprachiasmatic nucleus. Th e melatonin production in the night can be eff ectively suppressed by a light (Bojkowski et al 1987a;McIntyre et al 1989). Th e suppressive eff ect of the light depends on its duration, intensity, and wavelength.…”