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Blocking Low-Wavelength Light Prevents Nocturnal Melatonin Suppression with No Adverse Effect on Performance during Simulated Shift Work

Sleep Research Laboratory (L.K., R.J.H., B.P., S.A.C., S.S., C.M.S.), University Health Network, Toronto, Ontario, Canada M5T 2S8; and Departments of Psychiatry (L.K., R.J.H., C.M.S.), Obstetrics and Gynecology (R.F.C.), and Ophthalmology (C.M.S.), University of Toronto, Toronto, Ontario, Canada M5T 2Z9

Address all correspondence and requests for reprints to: Dr. Leonid Kayumov, Department of Psychiatry, University Health Network, ECW 3D-035, 399 Bathurst Street, Toronto, Ontario, Canada M5T 2S8. E-mail: lkayumov{at}uhnres.utoronto.ca.

Decreases in melatonin production in human and animals are known to be caused by environmental lighting, especially short-wavelength lighting (between 470 and 525 nm). We investigated the novel hypothesis that the use of goggles with selective exclusion of all wavelengths less than 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 (<5 lux), bright (800 lux), and filtered (800 lux) light at hourly intervals between 2000 and 0800 h in 11 healthy young males and eight females (mean age, 24.7 ± 4.6 yr). The measurements were performed during three nonconsecutive nights over a 2-wk period. Subjective sleepiness was measured by self-report scales, whereas 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, or alertness.