This Month (May 2017) in KI: Obesity and CKD
Obesity and new onset of CKD:
Obesity but not overweight increases risk of CKD (eGFR <60 and albuminuria) in the general population. A systematic review and Meta-analysis of 39 cohorts, 630,677 individuals showed an association between BMI >30kg/m2 and risk of low eGFR and albuminuria. Whilst many of the studies included adjusted the risk of CKD/Albuminuria to other risk factors associated with CD such as hypertension and smoking, the impact of obesity-related confounders remains unclear, in spite of adjustement for co-morbidities.
Concern has to be expressed over the use of MDRD eGFR estimation in the obese where it is poorly validated. Also, single measurement of eGFR does NOT define CKD...nephrologists seem to forget that a single eGFR value is not sufficient to label an individual as suffering from CKD as KDOQI recommends 2 of 3 positive values over a 3 months period as evidence of chronicity.
Finally, is BMI the best marker of obesity...as individuals with a high body weight due to a high muscle mass would have a higher serum creatinine than others and potentially a lower eGFR...whilst central obesity with a high abdominal fat content and a raised waist circumference/waist-Hip ratio seems a more accurate predictor of obesity-related outcomes...
This was recently highlighted in a study where there were no significant statistical interactions between WHR and obesity status (BMI) and central obesity was found to be associated with adverse cardiac dysfunction.
In other words, eGFR and BMI may be inaccurate parameters to evaluate the impact of OBESITY on RENAL FUNCTIONAL OUTCOMES; better studies need to be divised with more accurate measurements of both renal function and central obesity and better validation of CKD!
Compiling poor data, through meta-analysis, may improve quantity...but does not improve overall quality nor does it justify hasty conclusions.