title: Vitamin D supplementation to prevent depression and poor physical function in older adults: Study protocol of the D-Vitaal study, a randomized placebo-controlled clinical trial.
abstract: BACKGROUND
  Depressive symptoms and decreased physical functioning are interrelated conditions and common in older persons, causing significant individual and societal burden. Evidence suggests that vitamin D supplementation may be beneficial for both mental and physical functioning. However, previous randomized controlled trials have yielded inconsistent results and often had suboptimal designs. This study examines the effect of vitamin D supplementation on both depressive symptoms and physical functioning in a high-risk population of older persons with low vitamin D status.
  
  
  METHODS
  The D-Vitaal study is a randomized, double-blind, placebo-controlled trial investigating the effects of a daily dose of 1200 IU vitamin D3 versus placebo for one year on depressive symptoms and physical functioning (primary outcomes) in older adults. Participants (N = 155, age 60-80 years) were recruited from the general population. Eligibility criteria included the presence of depressive symptoms, ≥1 functional limitation and serum 25-hydroxyvitamin D levels between 15 and 50/70 nmol/L (depending on season). Secondary outcomes include incidence of major depressive disorder, anxiety symptoms, health-related quality of life, cognitive function and cost-effectiveness of the intervention.
  
  
  CONCLUSIONS
  With this study, we aim to elucidate the effects of vitamin D supplementation on depressive symptoms and physical functioning in older persons who are at high risk of developing more substantial mental and physical problems. If effective, vitamin D supplementation can be a preventive intervention strategy that is easy to implement in the primary care setting.
  
  
  BACKGROUND
  Netherlands Trial Register NTR3845. Registered 6 February 2013.
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. ej.dekoning@vumc.nl.|Department of Epidemiology and Biostatistics, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. ej.dekoning@vumc.nl.
authors.forename: Elisa J
authors.initials: EJ
authors.lastname: de Koning
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. nm.vanschoor@vumc.nl.|Department of Epidemiology and Biostatistics, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. nm.vanschoor@vumc.nl.
authors.forename: Natasja M
authors.initials: NM
authors.lastname: van Schoor
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. b.penninx@vumc.nl.|Department of Psychiatry, VU University Medical Center/GGZ inGeest, A.J. Ernststraat 1187, P.O. Box 1081 HL, Amsterdam, The Netherlands. b.penninx@vumc.nl.
authors.forename: Brenda W J H
authors.initials: BW
authors.lastname: Penninx
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. p.elders@vumc.nl.|Department of General Practice and Elderly Care Medicine, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. p.elders@vumc.nl.
authors.forename: Petra J M
authors.initials: PJ
authors.lastname: Elders
authors.affiliation: Department of Clinical Chemistry, Endocrine Laboratory, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. a.heijboer@vumc.nl.
authors.forename: Annemieke C
authors.initials: AC
authors.lastname: Heijboer
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. jh.smit@ggzingeest.nl.|Department of Psychiatry, VU University Medical Center/GGZ inGeest, A.J. Ernststraat 1187, P.O. Box 1081 HL, Amsterdam, The Netherlands. jh.smit@ggzingeest.nl.
authors.forename: Jan H
authors.initials: JH
authors.lastname: Smit
authors.affiliation: Department of Clinical Pharmacology and Pharmacy, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. pm.bet@vumc.nl.
authors.forename: Pierre M
authors.initials: PM
authors.lastname: Bet
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. maurits.van.tulder@vu.nl.|Department of Health Sciences, VU University, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. maurits.van.tulder@vu.nl.
authors.forename: Maurits W
authors.initials: MW
authors.lastname: van Tulder
authors.affiliation: Department of Internal Medicine, Endocrine section, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. m.denheijer@vumc.nl.
authors.forename: Martin
authors.initials: M
authors.lastname: den Heijer
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. harm.vanmarwijk@manchester.ac.uk.|Department of General Practice and Elderly Care Medicine, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. harm.vanmarwijk@manchester.ac.uk.|Primary Care Research Centre, Institute of Population Health, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom. harm.vanmarwijk@manchester.ac.uk.
authors.forename: Harm W J
authors.initials: HW
authors.lastname: van Marwijk
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. p.lips@vumc.nl.|Department of Internal Medicine, Endocrine section, VU University Medical Center, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands. p.lips@vumc.nl.
authors.forename: Paul
authors.initials: P
authors.lastname: Lips
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology*; D000368:Aged; D003071:Cognition / Q000187:drug effects*; D003863:Depression / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects*; D009426:Netherlands; D017063:Outcome Assessment, Health Care; D011788:Quality of Life; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D014815:Vitamins / Q000008:administration & dosage
chemical_list: D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D