Seasonal Variation in Human Illumination Exposure at Two Different Latitudes
Open Access
- 1 December 1995
- journal article
- research article
- Published by SAGE Publications in Journal of Biological Rhythms
- Vol. 10 (4), 324-334
- https://doi.org/10.1177/074873049501000406
Abstract
The authors measured ambient illumination exposure in healthy volun teers in San Diego, California (latitude 32° 43' N, n = 30), and Rochester, Minne sota (latitude 44° 1'N, n = 24), during each of the four quarters of the year, which were centered on the solstices and equinoxes. Subjects wore photosensors on their wrists and lapels (or foreheads while in bed) 24 h per day for an average of 5-6 days per quarter. The maximum of the two illumination readings was stored each minute. Annual average time spent per day in outdoor illumination (≥ 1000 lux) was significantly higher in San Diego than it was in Rochester (p <.04). Daily durations of illumination at or exceeding thresholds of 1,10,100,1000, and 10,000 lux were highly seasonal in the sample as a whole (p < .01 at 1 lux, p < .0001 at other thresholds). Seasonal variation in outdoor illumination was far more pronounced in Rochester than it was in San Diego (interaction p < .001) but remained significant in San Diego ( p ≤ .03). Seasonal variation in indoor illumi nation was generally similar in the two cities. The median Rochester subject experienced illumination ≥ 1000 lux for 2 h 23 min per day during summer and 23 min per day during winter. The corresponding times in San Diego were 2 h 10 min and 1 h 20 min. Neither age nor gender predicted illumination duration at any level. Both season and geographic location strongly influenced human illumination exposure, and behavior (choice of indoor vs. outdoor environment) was the most important mediating factor.Keywords
This publication has 9 references indexed in Scilit:
- Low illumination experienced by San Diego adults: Association with atypical depressive symptomsBiological Psychiatry, 1994
- Dawn simulation treatment of winter depression: a controlled studyAmerican Journal of Psychiatry, 1993
- Annual Rhythm of Human Reproduction: I. Biology, Sociology, or Both?Journal of Biological Rhythms, 1990
- Dawn and dusk simulation as a therapeutic interventionBiological Psychiatry, 1989
- Light therapy for Seasonal Affective Disorder A review of efficacyNeuropsychopharmacology, 1989
- Dose-response relationship between light irradiance and the suppression of plasma melatonin in human volunteersBrain Research, 1988
- Suppression of Nocturnal Plasma Melatonin and 6-Sulphatoxymelatonin by Bright and Dim Light in ManHormone and Metabolic Research, 1987
- Spectral, Irradiance, and Temporal Aspects of Natural and Artificial LightAnnals of the New York Academy of Sciences, 1985
- Use of Light to Treat Jet Lag: Differential Effects of Normal and Bright Artificial Light on Human Circadian RhythmsAnnals of the New York Academy of Sciences, 1985