The effect of dim light on suppression of nocturnal melatonin in healthy women and men.

The present study investigated the effect of dim white light on nocturnal plasma melatonin in males and females. Subjects were exposed to light between 2400 hr and 0100 hr. No significant gender differences were found with both 200 lux (p > 0.1) and 500 lux (p > 0.1) of light. Furthermore the amplitude of the melatonin rhythm was not significantly different with gender. This suggests that at low intensities the melatonin sensitivity to light is not differentially regulated between sexes.