Quantal melatonin suppression by exposure to low intensity light in man

Abstract

Plasma melatonin concentrations were examined following three relatively low intensities of artificial light. Six normal, healthy control subjects were all exposed to (a) 200 lux, (b) 400 lux and (c) 600 lux for a three hour duration from midnight to 0300 h. Blood was also collected on a control night where light intensity was less than 10 lux throughout. Significant suppression of melatonin was observed following light of 400 lux and 600 lux intensity when compared to the control night (p < 0.05; Mann-Whitney U-test). 200 lux light did not produce a statistically significant melatonin suppression when compared with control samples. Each light intensity produced its own individual maximal me..