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09-01-2012 | General practice | Article

Childhood chronic kidney disease linked to vitamin D deficiency


Free abstract

MedWire News: Vitamin D deficiency may increase the risk for chronic kidney disease (CKD) among children and adolescents, researchers report.

Although 25-hydroxyvitamin D (25[OH]D) deficiency is common among healthy children, the deficiency appears to be most common among those with late stage CKD (stages 4-5), remark the researchers.

Indeed, Heidi Kalkwarf (Cincinnati Children's Hospital Medical Center, Ohio, USA) and team found that when 25(OH)D levels were measured among 182 patients aged 5-21 years and with stage 2-5 CKD, nearly 50% were 25(OH)D deficient, defined as having 25(OH)D levels lower than 20 ng/mL.

By contrast, only 31% of 276 CKD-free participants of the same age had 25(OH)D deficiency.

When the prevalence of 25(OH)D deficiency was evaluated according to patient CKD severity, Kalkwarf and team found a positive correlation between 25(OH)D deficiency and CKD stage.

Specifically, 25(OH)D deficiency was present among 26% of 74 patients with stage 2-3 CKD, 50% of 54 patients with stage 4-5 CKD, and 74% of 54 patients with dialysis-dependent stage 5 CKD.

Hypoalbuminemia, defined as having an albumin level of less than 3 mg/dL, showed association with 25(OH)D deficiency, with a deficiency rate of 95% observed among 19 patients with the condition.

Furthermore, mean serum 25(OH)D concentrations were significantly lower among hypoalbuminemic children and adolescents than in those with normal serum albumin levels, at 11.1 and 23.5 ng/mL, respectively.

The researchers found that the presence of focal segmental glomerulosclerosis (FSGS) was an additional risk factor for 25(OH)D deficiency, irrespective of CKD stage and hypoalbuminemia.

In light of the known association between FSGS and proteinuria, the relationship between FSGS and vitamin D deficiency may be due to long-term urinary losses of vitamin D-binding protein, say Kalkwarf and colleagues.

They also highlight that failure to collect information on dietary vitamin D intake and sun exposure among the cohort leaves room for speculation about the underlying cause of the associations identified.

They explain: "It is possible that children and adolescents with CKD spend less time outdoors and that their vitamin D deficiency is attributable, in part, to sun exposure."

Nonetheless, Kalkwarf and team say that "vitamin D deficiency is a highly prevalent and modifiable risk factor in children and adolescents with CKD."

Writing in the journal Kidney International, the researchers conclude that vitamin D supplementation trials may help to determine if repletion of vitamin D levels can reduce CKD risk.

By Lauretta Ihonor

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