title: Duration of vitamin D synthesis from weather model data for use in prospective epidemiological studies.
abstract: In order to investigate the influence of solar radiation on vitamin D status and its association with different health outcomes in population based studies, appropriate estimates of the subjects' UV radiation exposure are needed. This unique study describes a method that estimates the daily number of vitamin D effective hours (VD-hours) at arbitrary ground locations throughout the period 1957-2002. The method is particularly suited for large-scale prospective epidemiological studies with questionnaire-based information on sun exposure, and where blood measures of vitamin D status are not available. The model takes total cloud cover fraction and total ozone column at noon as input from the ERA-40 data series (i.e. the 40 + year European Centre for Medium-Range Weather Forecasts Re-Analysis archive). By comparing the model results against high accuracy measurements at two different locations in Norway, we found the method for estimating the number of VD-hours to be accurate within 2.5 +/- 7% or better for moderate solar zenith angles (< 65 degrees). For higher solar zenith angles (> 65 degrees) the results are more variable, but the contribution to a population's vitamin D level from solar radiation when the sun is this low in the sky is rather small. The program code to compute VD-hours from ERA-40 files is written in Perl (v 5.8.7) and may be obtained free of charge by contacting corresponding author.
authors.affiliation: Institute of Community Medicine, Faculty of Medicine, University of Tromsø, 9037, Tromsø, Norway. ked@nilu.no
authors.forename: Kåre
authors.initials: K
authors.lastname: Edvardsen
authors.forename: Ola
authors.initials: O
authors.lastname: Engelsen
authors.forename: Magritt
authors.initials: M
authors.lastname: Brustad
mesh_terms: D016021:Epidemiologic Studies; D006801:Humans; D008962:Models, Theoretical; D009664:Norway / Q000453:epidemiology; D011446:Prospective Studies; D012621:Seasons; D012867:Skin / Q000378:metabolism / Q000528:radiation effects; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology; D012984:Software; D011795:Surveys and Questionnaires; D013997:Time Factors; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000096:biosynthesis* / Q000097:blood / Q000528:radiation effects*; D014808:Vitamin D Deficiency / Q000453:epidemiology / Q000517:prevention & control; D014887:Weather
chemical_list: D014807:Vitamin D