title: Serum 25-hydroxyvitamin D concentration is associated with functional capacity in older adults with heart failure.
abstract: BACKGROUND
  Vitamin D is a fat-soluble hormone necessary for calcium homeostasis. Recently, studies have demonstrated that vitamin D may be important to the health of the cardiovascular system.
  
  
  METHODS
  Adults ≥ 50 years of age with heart failure were recruited for assessment of serum 25-hydroxyvitamin D (25OHD) concentrations. Cardiopulmonary exercise testing was used to assess functional capacity. Proximal muscle strength was evaluated with a Biodex isokinetic dynamometer [corrected] (Biodex, Shirley, NY), and health status was assessed with the Kansas City Cardiomyopathy Questionnaire. Univariate associations between physical performance and health status measures and 25OHD followed by a linear regression model were used to study associations, adjusting for other potential explanatory variables.
  
  
  RESULTS
  Forty adults 67.8 ± 10.9 years of age (55% women and 57.5% African American) with mean ejection fraction 40% were analyzed (New York Heart Association class II in 70% and class III in 30%). Comorbidities included 77.5% hypertension and 47.5% diabetes. The mean 25OHD concentration was 18.5 ± 9.1 ng/mL, and mean peak Vo₂, 14 ± 4 mL/kg/min. In univariate regression analysis, 25OHD was positively associated with peak Vo₂ (P = .045). Multivariable regression analysis sustained positive association between 25OHD and peak Vo₂ (P = .044) after adjusting for age, race, and respiratory exchange ratio (adjusted R² = 0.32). Association between proximal muscle strength with the 25OHD concentration was not significant. The Kansas City Cardiomyopathy Questionnaire physical limitation domain score was negatively associated with 25OHD (P = .04) but was not sustained in multivariable analysis.
  
  
  CONCLUSIONS
  25-Hydroxyvitamin D may be an important marker or modulator of functional capacity in patients with heart failure. Randomized controlled trials are needed to assess the effect of vitamin D repletion on functional performance.
authors.affiliation: Department of Medicine, Case Western Reserve University, Cleveland, OH, USA. rebecca.boxer@case.edu
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Boxer
authors.forename: Anne M
authors.initials: AM
authors.lastname: Kenny
authors.forename: Vinay K
authors.initials: VK
authors.lastname: Cheruvu
authors.forename: Marianne
authors.initials: M
authors.lastname: Vest
authors.forename: Justin J
authors.initials: JJ
authors.lastname: Fiutem
authors.forename: Ileana I
authors.initials: II
authors.lastname: Piña
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D004311:Double-Blind Method; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000097:blood* / Q000188:drug therapy / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D011379:Prognosis; D012720:Severity of Illness Index; D013318:Stroke Volume / Q000502:physiology; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D014815:Vitamins / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D015415:Biomarkers; D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D