Blocking low-wavelength light prevents nocturnal melatonin suppression with no adverse effect on performance during simulated shift work

Decreases in melatonin production in human and animals are known to be caused by environmental lighting, especially short wavelength lighting (between 470 to 525 nm). We investigated the novel hypothesis that the use of goggles with selective exclusion of all wavelengths <530 nm could prevent the suppression of melatonin in bright light conditions during a simulated shift work experiment. Salivary melatonin levels were measured under dim light (<5 lux), bright light (800 lux) and filtered light (800 lux) at hourly intervals between 2000 h and 0800 h in 11 healthy young males and 8 females (mean age 24.7 ± 4.6 yr). The measurements were performed during 3 non-consecutive nights over a two-week period. Subjective sleepiness was measured by self-report scales while objective performance was assessed with the Continuous Performance Test. All subjects demonstrated preserved melatonin levels in filtered light similar to their dim light secretion profile. Unfiltered bright light drastically suppressed melatonin production. Normalization of endogenous melatonin production while wearing goggles did not impair measures of performance, subjective sleepiness nor alertness.