title: Non-linear relationship between serum 25-hydroxyvitamin D and hemoglobin in Korean females: the Korean National Health and Nutrition Examination Survey 2010-2011.
abstract: BACKGROUND
  Anemia and vitamin D deficiency are both important health issues; however, the nature of the association between vitamin D and either hemoglobin or anemia remains unresolved in the general population.
  
  
  METHODS
  Data on 11,206 adults were obtained from the fifth Korean National Health and Nutritional Examination Survey. A generalized additive model was used to examine the threshold level for relationship between serum 25-hydroxyvitamin D [25(OH)D] and hemoglobin levels. A multivariate logistic regression for anemia was conducted according to 25(OH)D quintiles. All analyses were stratified according to sex and menstrual status.
  
  
  RESULTS
  The generalized additive model confirmed a threshold 25(OH)D level of 26.4 ng/mL (male, 27.4 ng/mL; premenopausal females, 11.8 ng/mL; postmenopausal females, 13.4 ng/mL). The threshold level affected the pattern of association between 25(OH)D and anemia risk: the odds ratio of the 1(st) quintile but not the 2(nd), 3(rd), and 4(th) quintiles were significantly different from the 5(th) quintile in both premenopausal and postmenopausal females, however there was no obvious trend in males.
  
  
  CONCLUSIONS
  This population-based study demonstrated a non-linear relationship with a threshold effect between serum 25(OH)D and hemoglobin levels in females. Further interventional studies are warranted to determine whether the appropriate level of hemoglobin can be achieved by the correction of vitamin D deficiency.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seung Seok
authors.initials: SS
authors.lastname: Han
authors.forename: Myounghee
authors.initials: M
authors.lastname: Kim
authors.forename: Ho
authors.initials: H
authors.lastname: Kim
authors.forename: Su Mi
authors.initials: SM
authors.lastname: Lee
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Oh
authors.forename: Jung Pyo
authors.initials: JP
authors.lastname: Lee
authors.forename: Sejoong
authors.initials: S
authors.lastname: Kim
authors.forename: Kwon Wook
authors.initials: KW
authors.lastname: Joo
authors.forename: Chun Soo
authors.initials: CS
authors.lastname: Lim
authors.forename: Yon Su
authors.initials: YS
authors.lastname: Kim
authors.forename: Dong Ki
authors.initials: DK
authors.lastname: Kim
mesh_terms: D000740:Anemia / Q000097:blood* / Q000453:epidemiology*; D003625:Data Collection; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009752:Nutritional Status; D056910:Republic of Korea / Q000453:epidemiology; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D006454:Hemoglobins; D014807:Vitamin D; C104450:25-hydroxyvitamin D