title: Farming, Foreign Holidays, and Vitamin D in Orkney.
abstract: Orkney, north of mainland Scotland, has the world's highest prevalence of multiple sclerosis (MS); vitamin D deficiency, a marker of low UV exposure, is also common in Scotland. Strong associations have been identified between vitamin D deficiency and MS, and between UV exposure and MS independent of vitamin D, although causal relationships remain to be confirmed. We aimed to compare plasma 25-hydroxyvitamin D levels in Orkney and mainland Scotland, and establish the determinants of vitamin D status in Orkney. We compared mean vitamin D and prevalence of deficiency in cross-sectional study data from participants in the Orkney Complex Disease Study (ORCADES) and controls in the Scottish Colorectal Cancer Study (SOCCS). We used multivariable regression to identify factors associated with vitamin D levels in Orkney. Mean (standard deviation) vitamin D was significantly higher among ORCADES than SOCCS participants (35.3 (18.0) and 31.7 (21.2), respectively). Prevalence of severe vitamin D deficiency was lower in ORCADES than SOCCS participants (6.6% to 16.2% p = 1.1 x 10(-15)). Older age, farming occupations and foreign holidays were significantly associated with higher vitamin D in Orkney. Although mean vitamin D levels are higher in Orkney than mainland Scotland, this masks variation within the Orkney population which may influence MS risk.
authors.affiliation: Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, Scotland.
authors.forename: Emily
authors.initials: E
authors.lastname: Weiss
authors.affiliation: Public Health and Primary Care, Trinity College Centre for Health Sciences, Dublin, Ireland.
authors.forename: Lina
authors.initials: L
authors.lastname: Zgaga
authors.affiliation: Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, Scotland.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Read
authors.affiliation: Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, Scotland.
authors.forename: Sarah
authors.initials: S
authors.lastname: Wild
authors.affiliation: MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland.
authors.forename: Malcolm G
authors.initials: MG
authors.lastname: Dunlop
authors.affiliation: Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, Scotland.
authors.forename: Harry
authors.initials: H
authors.lastname: Campbell
authors.affiliation: Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, Scotland.
authors.forename: Ruth
authors.initials: R
authors.lastname: McQuillan
authors.affiliation: Usher Institute for Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, Scotland.|MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, Scotland.
authors.forename: James F
authors.identifier: 0000-0001-5751-9178
authors.initials: JF
authors.lastname: Wilson
mesh_terms: D000328:Adult; D000368:Aged; D000383:Agriculture; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000097:blood*; D015995:Prevalence; D000069079:Radiation Exposure; D012606:Scotland / Q000453:epidemiology; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000528:radiation effects; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D