Epidemiology of vitamin D deficiency in West African hemodialysis patients: A pilot study from Senegal

Sir,

Vitamin D deficiency is common in chronic kidney disease patients undergoing hemodialysis and is associated with bone disorders[1] and increased mortality.[2] Previous studies suggest that vitamin D deficiency is more frequent in patients with an African origin whose skin pigmentation is a barrier to ultraviolet rays necessary to 25-OH vitamin D synthesis.[13] Like in many developing regions, little is currently known about vitamin D status of dialysis patients from Sub-Saharan Africa.[4] Data from black populations living in the United States or Europe might not be applicable for African patients whose dietary habits and sunlight exposures are different. We report here a pilot study that aimed to determine the prevalence of vitamin D deficiency in Senegalese hemodialysis patients.

In a cross-sectional study between March 30^th and October 30^th 2011, we included 46 patients from two main hemodialysis centers in Dakar. Clinical data, serum calcium, phosphate and vitamin D levels during the last 3 months were collected from patients’medical records. All dosages of 25-OH vitamin D were performed using electrochemiluminescence immunoassay (COBAS Roche Diagnostics). Vitamin D deficiency was defined as a serum 25-OH vitamin D level <15 μg/l. Univariate and multivariate logistic regressions were used to identify the factors associated with vitamin D deficiency.

Mean age of patients was 50.3 ± 12.7 years (13-77 years) and 39.1% of them were females. All patients were dialyzed using the bicarbonate buffer and a calcium rich dialysate (1.75 mmol/l). Almost all of them (91%) had a weekly Kt/V >1.2. Thirty six patients (78.2%) presented pre-dialysis high blood pressure (≥140/90 mmHg) and six patients (13%) had a body mass index above 30 kg/m². The etiologies of end-stage renal disease were dominated by hypertension (39%) and diabetes (26%).

Prevalence of vitamin D deficiency was 32.6% and 28 patients (60.8%) had a vitamin D level between 15 μg/Land 30 μg/l). This prevalence was comparable between men and women (respectively 47.3% and 50.0%, P = 0.93). After multivariate logistic regression, age ≥50 years, hypocalcemia and hyperparathyroidism showed significant association of vitamin D deficiency, but gender and hyperphosphatemia did not [Table 1].

Table 1 Parameters associated with vitamin D deficiency

The present results show that the prevalence of vitamin D deficiency in hemodialysis patients living in Senegal is similar to those reported in Western countries.[135]

Despite limitation due to small sample size and the cross-sectional study design, this study could be a basis for larger prospective cohort that would also assess the effect of vitamin D deficiency on bone and cardiovascular outcomes in African dialysis patients.