title: Vitamin D status and seasonal changes in plasma concentrations of 25-hydroxyvitamin D in office workers in Ankara, Turkey.
abstract: BACKGROUND
  Lack of sun exposure is one of the primary causes of epidemic vitamin D deficiency worldwide. The aim of this study was to investigate vitamin D status and seasonal changes in summer and winter in office workers.
  
  
  METHODS
  This study was conducted in Ankara located at 39° 52' 30" N, 32° 52' E. The study consisted of 118 premenopausal women and men aged between 21 and 52 years-old. Seasonal changes were evaluated in August and February. Fasting serum was obtained for intact parathyroid hormone (iPTH) and 25-hydroxyvitamin D (25OHD). Additional data were collected by a questionnaire that enquired about age, weight, height, wearing style, dietary calcium intake and sunlight exposure. Serum 25OHD concentration was measured using a precise HPLC assay. Low vitamin D status was defined as a 25OHD concentration less than 30 ng/mL.
  
  
  RESULTS
  Mean serum 25OHD concentration in summer was 28.4±10.4 ng/mL and 13.8±6.6 ng/mL in winter (p<0.001). 35.6% of the subjects were vitamin D insufficient in summer and 12.7% in winter (p<0.001) while 31.5% were vitamin D deficient in summer and 83.9% in winter (p<0.001). A significant increase in iPTH levels (33.1±15.9 pg/mL vs 49.6±24.3 pg/mL, p<0.001) was observed throughout the seasonal change. No significant association was found between 25OHD levels and iPTH, body mass index, age and sun exposure index (p>0.05 for all) in both seasons.
  
  
  CONCLUSIONS
  Vitamin D deficiency is very prevalent in office workers even in summer time and this should be accepted as a public health problem.
authors.affiliation: Department of Endocrinology and Metabolism, Hacettepe University School of Medicine, 06100 Ankara, Turkey. Electronic address: cinarnese@gmail.com.
authors.forename: Nese
authors.initials: N
authors.lastname: Cinar
authors.affiliation: Department of Endocrinology and Metabolism, Hacettepe University School of Medicine, 06100 Ankara, Turkey.
authors.forename: Ayla
authors.initials: A
authors.lastname: Harmanci
authors.affiliation: Department of Endocrinology and Metabolism, Hacettepe University School of Medicine, 06100 Ankara, Turkey.
authors.forename: Bulent O
authors.initials: BO
authors.lastname: Yildiz
authors.affiliation: Department of Endocrinology and Metabolism, Hacettepe University School of Medicine, 06100 Ankara, Turkey.
authors.forename: Miyase
authors.initials: M
authors.lastname: Bayraktar
mesh_terms: D000328:Adult; D002136:Calcium, Dietary; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D016272:Occupational Health; D010281:Parathyroid Hormone / Q000097:blood*; D011446:Prospective Studies; D012621:Seasons; D012907:Smoking / Q000453:epidemiology; D013472:Sunlight; D014421:Turkey / Q000453:epidemiology; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: 25-Hydroxyvitamin D; Office workers; Parathyroid hormone; Seasonal changes