Influencing factors on serum 25-hydroxyvitamin D 3 levels in Japanese chronic hepatitis C patients

Background Serum 25-hydroxyvitamin D 3 levels are generally lower in chronic hepatitis C patients than in healthy individuals. The purpose of this study is to clarify the factors which affect serum 25-hydroxyvitamin D 3 levels using data obtained from Japanese chronic hepatitis C patients. Methods The subjects were 619 chronic hepatitis C patients. Serum 25-hydroxyvitamin D 3 levels were measured by using double-antibody radioimmunoassay between April 2009 and August 2014. Serum 25-hydroxyvitamin D 3 levels of 20 ng/mL or less were classified as vitamin D deficiency, and those with serum 25-hydroxyvitamin D 3 levels of 30 ng/mL or more as vitamin D sufficiency. The relationship between patient-related factors and serum 25-hydroxyvitamin D 3 levels was analyzed. Results The cohort consisted of 305 females and 314 males, aged between 18 and 89 years (median, 63 years). The median serum 25-hydroxyvitamin D 3 level was 21 ng/mL (range, 6–61 ng/mL). On the other hand, the median serum 25-hydroxyvitamin D 3 level in the healthy subjects was 25 ng/mL (range, 7–52), being significantly higher than that those in 80 chronic hepatitis C patients matched for age, gender, and season ( p = 1.16 × 10 −8 ). In multivariate analysis, independent contributors to serum 25-hydroxyvitamin D 3 deficiency were as follows: female gender ( p = 2.03 × 10 −4 , odds ratio = 2.290, 95 % confidence interval = 1.479–3.545), older age ( p = 4.30 × 10 −4 , odds ratio = 1.038, 95 % confidence interval = 1.017–1.060), cold season ( p = 0.015, odds ratio = 1.586, 95 % confidence interval = 1.095–2.297), and low hemoglobin level ( p = 0.037, odds ratio = 1.165, 95 % confidence interval = 1.009–1.345). By contrast, independent contributors to serum 25-hydroxyvitamin D 3 sufficiency were male gender ( p = 0.001, odds ratio = 3.400, 95 % confidence interval = 1.635–7.069), warm season ( p = 0.014, odds ratio = 1.765, 95 % confidence interval = 1.117–2.789) and serum albumin ( p = 0.016, OR = 2.247, 95 % CI = 1.163–4.342). Conclusions Serum 25-hydroxyvitamin D 3 levels in chronic hepatitis C Japanese patients were influenced by gender, age, hemoglobin level, albumin and the season of measurement.