title: Association of Body Mass Index with Clinical Outcomes in Non-Dialysis-Dependent Chronic Kidney Disease: A Systematic Review and Meta-Analysis.
abstract: BACKGROUND
  Previous studies have not shown a consistent link between body mass index (BMI) and outcomes such as mortality and kidney disease progression in non-dialysis-dependent chronic kidney disease (CKD) patients. Therefore, we aimed to complete a systematic review and meta-analysis study on this subject.
  
  
  METHODS
  We searched MEDLINE, EMBASE, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Cochrane Central Register of Controlled Trials (CENTRAL), and screened 7,123 retrieved studies for inclusion. Two investigators independently selected the studies using predefined criteria and assessed each study's quality using the Newcastle-Ottawa quality assessment scale. We meta-analyzed the results based on the BMI classification system by the WHO.
  
  
  RESULTS
  We included 10 studies (with a total sample size of 484,906) in the systematic review and 4 studies in the meta-analyses. The study results were generally heterogeneous. However, following reanalysis of the largest reported study and our meta-analyses, we observed that in stage 3-5 CKD, being underweight was associated with a higher risk of death while being overweight or obese class I was associated with a lower risk of death; however, obesity classes II and III were not associated with risk of death. In addition, reanalysis of the largest available study showed that a higher BMI was associated with an incrementally higher risk of kidney disease progression; however, this association was attenuated in our pooled results. For earlier stages of CKD, we could not complete meta-analyses as the studies were sparse and had heterogeneous BMI classifications and/or referent BMI groups.
  
  
  CONCLUSIONS
  Among the group of patients with stage 3-5 CKD, we found a differential association between obesity classes I-III and mortality compared to the general population, indicating an obesity paradox in the CKD population.
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, Calif., USA; Department of Population Health and Disease Prevention, Program in Public Health, Calif., USA.
authors.forename: Seyed-Foad
authors.initials: SF
authors.lastname: Ahmadi
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, Calif., USA.
authors.forename: Golara
authors.initials: G
authors.lastname: Zahmatkesh
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Mass., USA.
authors.forename: Emad
authors.initials: E
authors.lastname: Ahmadi
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, Calif., USA; Veterans Affairs Long Beach Healthcare System, Long Beach, Calif., USA.
authors.forename: Elani
authors.initials: E
authors.lastname: Streja
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, Calif., USA.
authors.forename: Connie M
authors.initials: CM
authors.lastname: Rhee
authors.affiliation: Department of Population Health and Disease Prevention, Program in Public Health, Calif., USA; Department of Statistics, Donald Bren School of Information and Computer Sciences, University of California Irvine, Irvine, Calif., USA; Department of Epidemiology, UCLA School of Public Health, Los Angeles, Calif., USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Gillen
authors.affiliation: Nephrology Division, Second University of Naples, Naples, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: De Nicola
authors.affiliation: Nephrology Division, Second University of Naples, Naples, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Minutolo
authors.affiliation: Division of Nephrology, Department of Medicine, University of Illinois at Chicago, Chicago, Ill., USA.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Ricardo
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Calif., USA; Memphis Veterans Affairs Medical Center, Memphis, Tenn., USA.
authors.forename: Csaba P
authors.initials: CP
authors.lastname: Kovesdy
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, Calif., USA; Department of Population Health and Disease Prevention, Program in Public Health, Calif., USA; Veterans Affairs Long Beach Healthcare System, Long Beach, Calif., USA; Department of Epidemiology, UCLA School of Public Health, Los Angeles, Calif., USA.
authors.forename: Kamyar
authors.initials: K
authors.lastname: Kalantar-Zadeh
keywords: Body mass index; Chronic kidney disease; End-stage renal disease; Mortality; Obesity paradox