Duration of Obesity Associated with Decrease in eGFR in Pediatric Cohort Study

According to Pierluigi Marzuillo, MD, PhD, and colleagues, the doubling in the prevalence of chronic kidney disease during the past two decades may, in part, be a result of the epidemic increase of obesity. Gaining an understanding of the pathophysiology of estimated glomerular filtration rate (eGFR) in childhood obesity could enable identification of pediatric patients exposed to factors that could impact eGFR, requiring specific and intensive clinical management.

Dr. Marzuillo et al. conducted a retrospective, cross-sectional study designed to examine which clinical and metabolic factors could influence levels of eGFR in a large population of obese children with no evidence of primary kidney disease. Results of the study were reported in the Journal of Renal Nutrition [2018;28(5):359-362].

The study enrolled 2957 obese children and adolescents who consecutively attended the department of woman, child and of general and specialized surgery at Università degli Studi della Campania “Luigi Vanvitelli”, Naples, Italy, between January 2000 and January 2017. Of the total cohort, 1485 were female and participant age ranged from 3 to 18 years.

Inclusion criteria were body mass index (BMI) >95th percentile and eGFR >90 mL/min/1.73 m2. Exclusion criteria were secondary forms of obesity, eGFR <90 mL/min/1.73 m2, the presence of proteinuria or hematuria at urine dipstick, or consumption of any medication.

Data on weight, waist circumference, height, weight-to-height (W/H) ratio, BMI-standard deviation score (SDS), pubertal stage, systolic blood pressure and diastolic blood pressure, duration of obesity, insulin, eGFR, and homeostasis model assessment (HOMA-IR) were obtained. Multiple variable analyses were performed utilizing a general linear model.

The cohort was stratified into tertiles for BMI-SDS, W/H ratio, systolic blood pressure and diastolic blood pressure SDS, HOMA-IR, and duration of obesity. The main outcome measure was eGFR levels among those tertiles. Mean age of the cohort was 10.3 years, mean BMI-SDS was 2.9, and 33.78% (n=999/2957) were pubertal; eGFR values were similar in males and females.

Across the BMI-SDS and W/H ratio tertiles, there was significant increase in eGFR levels. Across systolic blood pressure-SDS, HOMA-IR, and duration of obesity tertiles, there was significant decrease in eGFR levels. Among pubertal patients, eGFR values were significantly lower compared with prepubertal patients. There were no significant differences in eGFR levels detected across diastolic blood pressure-SDS tertiles.

In a general linear model for eGFR variance, covariates were W/H ratio, HOMA-IR, duration of obesity, pubertal stage, BMI-SDS, and systolic blood pressure-SDS (model R2 39.7%: model P<.0001). The model confirmed the direct association between eGFR values and BMI-SDS; there was also an indirect association between eGFR values and HOMA-IR, duration of obesity, pubertal stage, and systolic blood pressure-SDS. Duration of obesity was the most significantly associated variable.

The researchers cited the cross-sectional design and the lack of data regarding the duration of obesity in all of the participants as limitations to the study.

In summary, the researchers said, “In conclusion, we think that this clinical observation adds another piece to the puzzle of the current knowledge about the effect of obesity on renal function. Beginning in childhood, longer duration of obesity could affect the eGFR negatively. Specific weight loss and blood pressure control programs could be useful to prevent reduction of eGFR values in childhood obesity, especially in adolescence, and later in adulthood. Pediatric patients and their parents should be aware of effects of obesity on eGFR levels over time and that puberty can further determine eGFR level reduction.”

Takeaway Points

  1. Researchers in Italy conducted a retrospective cross-sectional study to examine the clinical and metabolic factors that could influence estimated glomerular filtration rate (eGFR) levels in children and adolescents with obesity.
  2. Levels of eGFR significantly increased across tertiles of body mass index-standard deviation scores (SDS) and weight/height ratio tertiles.
  3. There was significant decrease in eGFR levels across tertiles of systolic blood pressure-SDS, homeostasis model assessment, and duration of obesity.