Mortality and Renal Outcomes Are Impacted by Obesity in Cardiorenal Metabolic Disease but Not in People with Concomitant Diabetes Mellitus

Introduction: Mounting evidence in the literature describes a reverse association, whereby obesity may have a protective effect on mortality - the "obesity paradox." Due to the significant overlap between elements of cardiorenal metabolic disease, we examined the effects of obesity on outcomes in a cohort of patients with non-dialysis chronic kidney disease (ND-CKD) by grouping patients according to their level of cardiometabolic co-morbidity to reduce the risk of bias.

Methods: This study was undertaken on all patients with a documented body mass index (BMI) in the Salford Kidney Study database from October 2002 until December 2016. Patients were grouped according to their BMI into normal weight, overweight, and obese, and also according to their level of co-morbidity into 4 groups: group 1 had CKD only; group 2 had CKD and heart failure (HF); group 3 had CKD and diabetes mellitus (DM); and group 4 had CKD, DM, and HF. Univariate and multivariate Cox regression analyses were performed.

Results: A total of 2,416 patients were included in the analysis. The median age was 67.3 years, 61.8% were male, and 96.4% were Caucasian. Obesity was associated with a lower incidence of combined outcomes in patients with ND-CKD who did not have DM (hazard ratio [HR] 0.74; p = <0.001 and HR 0.48; p = 0.008 for CKD alone and CKD + HF groups, respectively). This protective effect remained significant after correcting for major factors. In patients with ND-CKD and DM, there was no difference in all-cause mortality between the normal weight group and the obesity groups.

Conclusion: Obesity may be protective against adverse outcomes only in groups 1 (CKD alone) and 2 (CKD + HF). This "protective" effect was not seen in patients who had concomitant diabetes. These data suggest that diabetes is a potent predictor of adverse outcomes, irrespective of BMI; however, in patients without diabetes, obesity may play a protective role.