title: Vitamin D Deficiency in Unselected Patients from Swiss Primary Care: A Cross-Sectional Study in Two Seasons.
abstract: BACKGROUND
  As published data on 25-hydroxy-cholecalciferol (25(OH)D) deficiency in primary care settings is scarce, we assessed the prevalence of hypovitaminosis D, potential associations with clinical symptoms, body mass index, age, Vitamin D intake, and skin type in unselected patients from primary care, and the extent of seasonal variations of serum 25(OH)D concentrations.
  
  
  RESULTS
  25(OH)D was measured at the end of summer and/or winter in 1682 consecutive patients from primary care using an enzyme-linked immunosorbant assay. Clinical symptoms were assessed by self-report (visual analogue scale 0 to 10), and vitamin D deficiency was defined as 25(OH)D concentrations < 50 nmol/l. 25(OH)D deficiency was present in 995 (59.2%) patients. 25(OH)D deficient patients reported more intense muscle weakness (visual analogue scale 2.7, 95% confidence interval 2.5 to 2.9) and had a higher body mass index (25.9kg/m2, 25.5 to 26.2) than non-deficient patients (2.5, 2.3 to 2.7; and 24.2, 23.9 to 24.5, respectively). 25(OH)D concentrations also weakly correlated with muscle weakness (Spearman's rho -0.059, 95% confidence interval -0.107 to -0.011) and body mass index (-0.156, -0.202 to -0.108). Self-reported musculoskeletal pain, fatigue, and age were not associated with deficiency, nor with concentrations. Mean 25(OH)D concentrations in patients with vitamin D containing medication were higher (60.6 ± 22.2 nmol/l) than in patients without medication (44.8 ± 19.2 nmol/l, p < 0.0001) but still below the targeted level of 75 nmol/l. Summer and winter 25(OH)D concentrations differed (53.4 ± 19.9 vs. 41.6 ± 19.3nmol/l, p < 0.0001), which was confirmed in a subgroup of 93 patients who were tested in both seasons (p = 0.01).
  
  
  CONCLUSIONS
  Nearly 60% of unselected patients from primary care met the criteria for 25(OH)D deficiency. Self-reported muscle weakness and high body mass index were associated with lower 25(OH)D levels. As expected 25(OH)D concentrations were lower in winter compared to summer.
authors.affiliation: Institute of Primary and Community Care, Schwanenplatz 7, 6004, Luzern, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Merlo
authors.affiliation: Laboratories Bioanalytica, Maihofstrasse 95A, 6006, Luzern, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Trummler
authors.affiliation: Institute of Primary and Community Care, Schwanenplatz 7, 6004, Luzern, Switzerland; Swiss Paraplegic Research, Guido A. Zäch Strasse 4, 6207, Nottwil, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Essig
authors.affiliation: Center for Primary Health Care, University of Basel, Rheinstrasse 26, 4410, Liestal, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Zeller
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002112:Calcifediol / Q000097:blood; D002648:Child; D003430:Cross-Sectional Studies; D005221:Fatigue / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000150:complications; D010146:Pain / Q000150:complications; D011320:Primary Health Care / Q000706:statistics & numerical data*; D012621:Seasons; D012867:Skin / Q000378:metabolism; D013557:Switzerland / Q000453:epidemiology; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000453:epidemiology* / Q000378:metabolism; D055815:Young Adult
chemical_list: D002112:Calcifediol