Body adiposity predictors of vitamin D status in nondialyzed patients with chronic kidney disease: A cross-sectional analysis in a tropical climate city.

OBJECTIVES

The association of vitamin D status with high body adiposity is poorly investigated in the chronic kidney disease (CKD) population. The aim of the present study was to describe vitamin D status and to identify body adiposity predictors of vitamin D deficiency, in a nondialyzed CKD population inhabiting a tropical city.

METHODS

This cross-sectional study included patients with CKD, defined as estimated glomerular filtration rate (eGFR) <60 mL/min, regularly treated by an interdisciplinary team in an outpatient university clinic, set in a Brazilian city (latitude: 22°54'S; 43°12'W). Adiposity parameters analyzed were body mass index (BMI), total body adiposity (dual-energy x-ray absorptiometry [DXA] and body adiposity index [BAI]), and central body adiposity (DXA-trunk fat and waist-to-height ratio [WHtR]). Laboratory parameters included serum concentrations of 25-hydroxyvitamin D, phosphate, parathyroid hormone, and insulin (insulin resistance [IR evaluation: homeostasis model assessment; HOMA]).

RESULTS

We studied 244 patients (54.9% men; n = 134) with median eGFR = 29.1 mL/min and BMI 26.1 kg/m2, comprising 58.2% (n = 142) with overweight/obesity. The vitamin D status was sufficient (≥30 ng/dL) in 43%, insufficient (20-30 ng/dL) in 37%, and deficient (<20 ng/dL) in 20%. Total body adiposity was the independent predictor of vitamin D deficiency (DXA: odds ratio [OR], 2.3; 95% confidence interval [CI], 1.1-5; P = 0.03; BAI: OR, 1.9; 95% CI, 1-3.8; P = 0.02), whereas BMI, DXA-trunk fat, and WHtR showed no correlation. Higher serum phosphorus and hyperparathyroidism were related (P < 0.05) to vitamin D deficiency. IR was not independently associated with 25-hydroxyvitamin D concentration.

CONCLUSIONS

Just under half of the CKD population presented sufficient concentration of 25-hydroxyvitamin D. Total body adiposity, independent of age and eGFR, regardless if evaluated by DXA or BAI, was the predictor of vitamin D deficiency, which in turn was associated with higher serum phosphorus and hyperparathyroidism, but not with IR.