title: Non-linear association of serum 25-hydroxyvitamin D with urinary albumin excretion rate in normoalbuminuric subjects.
abstract: BACKGROUND
  Vitamin D deficiencies and increases in urinary albumin excretion (UAE) are both important and potentially related health problems; however, the nature of their relationship has not been established in normoalbuminuric subjects.
  
  
  METHODS
  We obtained data from 14,594 normoalbuminuric Korean adults who underwent voluntary health screenings. We used a generalized additive model to examine the threshold level for relationship between serum 25-hydroxyvitamin D [25(OH)D] and urinary-albumin creatinine ratio (UACR) levels. We conducted multivariate logistic regression for high-normal UAE (UACR, 10-29 mg/g), according to various categories of vitamin D status.
  
  
  RESULTS
  The generalized additive model confirmed a non-linear relationship between serum 25(OH)D and UACR levels, and the threshold concentration of 25(OH)D was 8.0 ng/mL after multivariate adjustment. Comparing subjects who fell into the lowest category of serum 25(OH)D levels with subjects who were in the reference range (the highest category), we observed that the multivariate adjusted odds ratio (OR) for high-normal UAE was significantly increased, regardless of the criteria used to categorize vitamin D levels: OR of the 1st quartile over the 4th quartile, 1.20 (95% CI, 1.04-1.39); OR of the 1.0-4.9th percentile over the 50-100th percentile, 1.56 (95% CI, 1.25-1.93); and OR of vitamin D deficiency group over vitamin D sufficiency group, 1.28 (95% CI, 1.08-1.52).
  
  
  CONCLUSIONS
  We demonstrated that there was an inverse relationship between serum 25(OH)D less than 8.0 ng/mL and UACR in normoalbuminuric subjects, suggesting that severe vitamin D deficiency could cause an increase in UAE in subjects with normoalbuminuria.
authors: Yun Jung
authors: YJ
authors: Oh
authors: Rae Woong
authors: RW
authors: Park
authors: Dukyong
authors: D
authors: Yoon
authors: Myounghee
authors: M
authors: Kim
authors: Seung Seok
authors: SS
authors: Han
authors: Hye Ryoun
authors: HR
authors: Jang
authors: Hyosang
authors: H
authors: Kim
authors: Nam Ju
authors: NJ
authors: Heo
authors: Su-Kil
authors: SK
authors: Park
authors: Hajeong
authors: H
authors: Lee
authors: Kwon Wook
authors: KW
authors: Joo
authors: Chun-Soo
authors: CS
authors: Lim
authors: Yon Su
authors: YS
authors: Kim
authors: Department of Internal Medicine, Seoul National University College of Medicine, 101 Daehak-ro, Jongro-gu Seoul 110-744, Korea. dkkim73@gmail.com.
authors: Dong Ki
authors: DK
authors: Kim
mesh_terms: D000419:Albuminuria / Q000097:blood* / Q000652:urine*; D000465:Algorithms; D015415:Biomarkers / Q000097:blood / Q000652:urine; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D017711:Nonlinear Dynamics; D012016:Reference Values; D015203:Reproducibility of Results; D056910:Republic of Korea; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D