Association of Body Mass Index with Outcomes in Patients with CKD

Abstract

Obesity is associated with higher mortality in the general population, but this association is reversed in patients on dialysis. The nature of the relationship of obesity with adverse clinical outcomes in nondialysisdependent CKD and the putative interaction of the severity of disease with this association are unclear. We analyzed data from a nationally representative cohort of 453,946 United States veterans with eGFR,60 ml/min per 1.73 m 2 . The associations of body mass index categories (,20, 20 to ,25, 25 to ,30, 30 to ,35, 35 to ,40, 40 to ,45, 45 to ,50, and $50 kg/m 2 ) with all-cause mortality and disease progression (using multiple definitions, including incidence of ESRD, doubling of serum creatinine, and the slopes of eGFR) were examined in Cox proportional hazards models and logistic regression models. Multivariable adjustments were made for age, race, comorbidities and medications, and baseline eGFR. Body mass index showed a relatively consistent U-shaped association with clinical outcomes, with the best outcomes observed in overweight and mildly obese patients. Body mass index levels ,25 kg/m 2 were associated with worse outcomes in all patients, independent of severity of CKD. Body mass index levels $35 kg/m 2 were associated with worse outcomes in patients with earlier stages of CKD, but this association was attenuated in those patients with eGFR,30 ml/min per 1.73 m 2 . Thus, until clinical trials establish the ideal body mass index, a cautious approach to weight management is warranted in this patient population.

Obesity and kidney disease: hidden consequences of the epidemic

“…Considering the above evidence about the overwhelmingly deleterious effects of obesity on various disease processes, it is seemingly counterintuitive that obesity has been consistently associated with lower mortality rates in patients with advanced CKD [19,61] and ESRD [62,63]. Similar "paradoxical" associations have also been described in other populations, such as in patients with congestive heart failure [64], chronic obstructive pulmonary disease [65], rheumatoid arthritis [66], and even in old individuals [67].…”

“…Furthermore, in numerous large population-based studies, higher BMI appears associated with the presence [8,12] and development of low estimated GFR [9][10][11][12][13], with more rapid loss of estimated GFR over time [14], and with the incidence of ESRD [15][16][17][18]. Elevated BMI levels, class II obesity and above, have been associated with more rapid progression of CKD in patients with pre-existing CKD [19]. A few studies examining the association of abdominal obesity using WHR or WC with CKD, describe an association between higher girth and albuminuria [20], decreased GFR [8] or incident ESRD [21] independent of BMI level.…”

Obesity and kidney disease: hidden consequences of the epidemic

“…Furthermore, in numerous large population-based studies, higher BMI appears associated with the presence 8,12 and development of low estimated GFR 9,10,13 , with more rapid loss of estimated GFR over time, 14 and with the incidence of ESRD [15][16][17][18] . Elevated BMI levels, class II obesity and above, have been associated with more rapid progression of CKD in patients with pre-existing CKD 19 . A few studies examining the association of abdominal obesity using WHR or WC with CKD, describe an association between higher girth and albuminuria 20 , decreased GFR 8 or incident ESRD 21 independent of BMI level.…”

“…Considering the above evidence about the overwhelmingly deleterious effects of obesity on various disease processes, it is seemingly counterintuitive that obesity has been consistently associated with lower mortality rates in patients with advanced CKD 19,61 and ESRD 62,63 . Similar "paradoxical" associations have also been described in other populations, such as in patients with congestive heart failure 64 , chronic obstructive pulmonary disease 65 , rheumatoid arthritis 66 , and even in old individuals 67 .…”

Misclassification of Obesity in CKD

“…However, a recent report including half a million United States veterans with CKD showed that low BMI categories equally associate with those risks (5). A recurrent discussion in such association studies is that BMI, when used in isolation, gives distorted prognostic information.…”