BOSTON—Study findings presented at the National Kidney Foundation’s 2016 Spring Clinical Meetings challenge whether obesity has an association with  chronic kidney disease (CKD).

“Much of the medical literature states that there is a direct effect of obesity on CKD, independent from the effects of diabetes and hypertension as a result of obesity,” lead researcher Patrick Albertus, MPH, of the Kidney Epidemiology and Cost Center at the University of Michigan in Ann Arbor, told Renal & Urology News. “Our findings from a large survey, which is demographically representative of the U.S. population, suggest that this direct effect is in question. Clinically, this could mean that control of diabetes, hypertension, and other mediators of this obesity-CKD pathway may be sufficient for a reduced risk of CKD.”

Albertus and his colleagues analyzed data from 16,700 participants in the National Health and Nutrition Examination Survey (2007–2012). Of these, 18.1% had CKD and 81.9% did not. Before adjusting for potential confounders and mediators, the researchers found a positive association between obesity (defined as a body mass index [BMI] above 30 kg/m2) and CKD. After adjustment, however, the association diminished or became negative, except among underweight individuals (BMI less than 18.5 kg/m2).

Albertus said this cross-sectional study should be interpreted with caution. A longitudinal cohort and more advanced statistical methods are needed to truly understand the direct effect of obesity on CKD, “but our results certainly show that more research concerning this question is necessary.”

Importantly, Albertus noted, the study found that the observed association between BMI and CKD prevalencediffered depending on the measure of kidney function used as an outcome. For example, urine albumin-to-creatinine ratio (uACR) measurements resulted in a strong positive association for underweight subjects compared with those of normal weight, whereas estimated glomerular filtration rates (eGFR) did not.

“Our findings related to the outcome measure suggest that we need to be aware of the measure of kidney function used to evaluate the association between obesity and CKD. Ideally, eGFR and uACR would need to be used.”