Nonlinear Associations Between Kidney Function Markers and Body Mass Index Among Women of Reproductive Age in Bangladesh

Background Normal kidney function is essential for maintaining good health. The objective of the study was to explore the association between socio-demographic characteristics and body mass index (BMI) with serum uric acid, urea, and creatinine levels among women of reproductive age (WRA) in selected areas of Bangladesh. Methodology A cross-sectional study was conducted among 178 WRA in selected districts of Bangladesh. Data on demographic, socioeconomic, and anthropometric variables were collected. Blood samples were collected, processed, stored, and analyzed using the DIALAB GmbH semi-automatic biochemistry analyzer DTN-405 (Austria) to measure uric acid, urea, and creatinine. Results The study found that 42 women (23.6%) were underweight, while 35 (19.7%) were classified as overweight or obese. The average (mean ± SD) serum levels (mg/dL) were 5.74 ± 2.07 for uric acid, 17.93 ± 9.83 for urea, 0.89 ± 0.28 for creatinine, and 92.18 ± 35.86 mL/min/1.73 m² for estimated glomerular filtration rate (eGFR). Elevated levels of creatinine, uric acid, and urea were observed in 47 (27%), 56 (31.5%), and 73 (41%) participants, respectively. Additionally, chronic kidney disease (CKD) was identified in 32 individuals (18%). Overall, normal kidney function markers were found in 55 participants (about 31%), while 9 participants (about 5%) showed elevated levels for all three markers. The odds of having one or more elevated kidney function markers were significantly higher (adjusted odds ratio (AOR) = 2.8; 95% CI: 1.22-6.42; p < 0.05) among individuals with a BMI greater than 18.5 kg/m² compared to underweight women. After adjusting for related factors, BMI was found to be significantly associated with the risk of elevated kidney function markers. Conclusion Only one-third of the WRA displayed normal kidney function indicators, and BMI demonstrated a significant non-linear relationship with one or more elevated kidney function indicators, even within the normal BMI range. Therefore, further studies with larger sample sizes are necessary to gain deeper insights.