Research

Daily illumination exposure and melatonin: influence of ophthalmic dysfunction and sleep duration

Girardin Jean-Louis^1,2,3 , Daniel F Kripke⁴ , Jeffrey A Elliott⁴ , Ferdinand Zizi^1,2 , Arthur H Wolintz^1,2 and Douglas R Lazzaro¹

¹  Department of Psychiatry and Ophthalmology, SUNY Downstate Medical Center, New York, NY

²  Brooklyn Research Foundation on Minority Health, KJMC, New York, NY

³  Department of Psychiatry, Maimonides Medical Center, New York, NY

⁴  Department of Psychiatry, University of California, San Diego, CA

author email corresponding author email

Journal of Circadian Rhythms 2005, 3:13doi:10.1186/1740-3391-3-13

Published:	1 December 2005

Abstract

Background

Ocular pathology lessens light's efficacy to maintain optimal circadian entrainment. We examined whether ophthalmic dysfunction explains unique variance in melatonin excretion of older adults over and above the variance explained by daily illumination, medical, and sociodemographic factors. We also examined whether ophthalmic dysfunction influences relationships between ambient illumination and melatonin.

Methods

Thirty older adults (mean age = 69 years; Blacks = 42% and Whites = 58%) of both genders participated in the study. Demographic and health data were collected at baseline. Participants underwent eye exams at SUNY Downstate Medical Center, wore an actigraph to monitor illumination and sleep, and collected urine specimens to estimate aMT6s concentrations.

Results

Hierarchical regression analysis showed that illumination factors explained 29% of the variance in aMT6s mesor. The proportion of variance explained by ophthalmic factors, sleep duration, and race was 10%, 2%, and 2%, respectively. Illumination factors explained 19% of the variance in aMT6s acrophase. The proportion of variance explained by ophthalmic factors, sleep duration, and race was 11%; 17%; and 2%, respectively. Controlling for sleep duration and race reduced the correlations between illumination and melatonin, whereas controlling for ophthalmic factors did not.

Conclusion

Ophthalmic exams showed that elevated intraocular pressure and large cup-to-disk ratios were independently associated with earlier melatonin timing. Lower illumination exposure also had independent associations with earlier melatonin timing. Conceivably, ophthalmic and illumination factors might have an additive effect on the timing of melatonin excretion, which in turn might predispose individuals to experience early morning awakenings.