Seasonal variation of vitamin D in patients on hemodialysis

Seasonal and racial differences in serum 25-hydroxyvitamin D levels have been studied extensively in the general population but not in patients with end-stage renal disease (ESRD).

Serum 25-hydroxyvitamin D levels, the best available index of vitamin D nutrition, was measured at the end of summer (September) in 142 chronic hemodialysis patients and again at the end of winter (April) in 73 of these 142 patients, to determine the prevalence and risk factors for vitamin D deficiency.

The prevalence of vitamin D depletion, as defined by serum 25-hydroxyvitamin D level of less than 20 ng/ml (50 nmol/l), was 54% at the end of summer and further increased to 86% by the end of winter (p < 0.0001 summer vs. winter). We observed that women and African-Americans had a greater prevalence of hypovitaminosis D (p < 0.0002 and p < 0.001 for both comparisons, respectively). Surprisingly, diabetic status, age, and the duration of esrd were not associated with a significant increase in risk of vitamin d depletion.

Vitamin D depletion is present in about half of ESRD patients with marked seasonal variations. Patients with ESRD should have more frequent assessments of their vitamin D nutrition by serum 25-hydroxyvitamin D levels, and vitamin D supplementation should be routinely prescribed, which may prevent many of the complications related to vitamin D deficiency and secondary hyperparathyroidism.