Association between body mass index and estimated glomerular filtration rate in patients with chronic kidney disease of unknown aetiology in Sri Lanka.

Chronic kidney disease of unknown aetiology (CKDu), which is widespread in the North Central Province (NCP) of Sri Lanka, is not associated with commonly known factors such as diabetes, hypertension, and glomerulonephritis. The pathogenicity of CKDu is not well understood, but people with a low body mass index (BMI) and mineral and nutrient deficiencies are more vulnerable to develop CKDu. To understand this situation, the relationship between BMI and the estimated glomerular filtration rate (eGFR) was investigated in people with CKDu in comparison with unaffected age-matched control groups in disease-endemic areas of the NCP. This community-based cross-sectional study was performed in Medirigiriya in the Polonnaruwa district of Sri Lanka, which has one of the highest densities of patients with CKDu. The data for identifying demographic factors and the relationship between CKDu and BMI were investigated by using a validated survey questionnaire. Findings indicated that the group with the highest number of people affected with CKDu (i.e. eGFR of less than 60 mL/min/1.73 m) had the lowest BMI compared to those with normal eGFR. The majority affected were male farmers. The severity of the disease was inversely associated with BMI values and had a higher prevalence of smoking and alcohol consumption. In addition, those who consume water from household dug wells had significantly lower eGFR (p < 0.0001). A linear regression analysis revealed a significant positive association between lower eGFR and lower BMI (p < 0.001). We hypothesised that the low BMI in those with CKDu may have increased susceptibility to develop CKDu, in the presence of exposure to multiple nephrotoxins and adverse conditions.