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Open Access Research article

Non-linear association of serum 25-hydroxyvitamin D with urinary albumin excretion rate in normoalbuminuric subjects

Yun Jung Oh12, Rae Woong Park34, Dukyong Yoon4, Myounghee Kim5, Seung Seok Han1, Hye Ryoun Jang6, Hyosang Kim7, Nam Ju Heo8, Su-Kil Park7, Hajeong Lee1, Kwon Wook Joo1, Chun-Soo Lim1, Yon Su Kim1 and Dong Ki Kim1*

Author Affiliations

1 Department of Internal Medicine, Seoul National University College of Medicine, 101 Daehak-ro, Jongro-gu Seoul 110-744, Korea

2 Department of Internal Medicine, Cheju Halla General Hospital, Jeju, Korea

3 Center for Clinical Epidemiology and Biostatistics, and Department of Biostatistics & Epidemiology and Center for Pharmacoepidemiololgy Research and Training, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA

4 Department of Biomedical Informatics, Ajou University School of Medicine, Suwon, Korea

5 Department of Dental Hygiene, College of Health Science, Eulji University, Seongnam, Korea

6 Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

7 Department of Internal Medicine, University of Ulsan college of Medicine, Asan Medical Center, Seoul, Korea

8 Department of Internal Medicine, Healthcare System Gangnam Center, Seoul National University Hospital, Seoul, Korea

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BMC Nephrology 2014, 15:97  doi:10.1186/1471-2369-15-97

Published: 24 June 2014

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.

Keywords:
Epidemiology; Low-grade albuminuria; Threshold; Vitamin D deficiency