title: Association of age and BMI with kidney function and mortality: a cohort study.
abstract: BACKGROUND
  Compared with normal weight, obesity might be associated with worse clinical outcomes, including chronic kidney disease. Whether this association is modified by age is not known. We investigated the association of BMI with progressive loss of kidney function and all-cause mortality in US veterans.
  
  
  METHODS
  In a national cohort of 3,376,187 US veterans with an estimated glomerular filtration rate (eGFR) of more than 60 mL/min per 1·73 m(2), we assessed the association of BMI in patients of different ages (<40 years, 40 years to <50 years, 50 years to <60 years, 60 years to <70 years, 70 years to <80 years, and ≥80 years) with loss of kidney function and with all-cause mortality in logistic regression models and Cox proportional hazards models adjusted for ethnic origin, sex, comorbidities, medications, and baseline eGFR.
  
  
  RESULTS
  274,764 (8·1%) of 3,376,187 veterans had a rapid decline in kidney function (decrease in slope of >5 mL/min per 1·73 m(2)). The lowest risk for loss of kidney function was noted in patients with BMI of at least 25 kg/m(2) but less than 30 kg/m(2). A generally consistent U-shaped association was noted between BMI and rapid loss of kidney function that was more prominent with increasing age, except in the patients younger than 40 years, in whom BMI did not seem to be predictive of renal function impairment. 672,341 veterans died (28·7 per 1000 patient-years, 95% CI 28·6-28·7) over a median follow-up of 6·8 years (IQR 6·5-7·7). BMI also showed a U-shaped association with mortality, which was similar in all age groups.
  
  
  CONCLUSIONS
  A BMI of 30 kg/m(2) or more is associated with rapid loss of kidney function in patients with eGFR of at least 60 mL/min per 1·73 m(2), and this association is accentuated in older patients. A BMI of 35 kg/m(2) or more is also associated with high mortality. A BMI of at least 25 kg/m(2) but less than 30 kg/m(2) is associated with the best clinical outcomes.
  
  
  BACKGROUND
  National Institute of Health, Memphis VA Medical Center, Long Beach VA Healthcare System, Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Health Services Research and Development, and VA Information Resource Center.
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Jun Ling
authors.initials: JL
authors.lastname: Lu
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Miklos Z
authors.initials: MZ
authors.lastname: Molnar
authors.affiliation: Division of Nephrology, Memphis Veteran Affairs Medical Center, Memphis, TN, USA.
authors.forename: Adnan
authors.initials: A
authors.lastname: Naseer
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA.
authors.forename: Margit K
authors.initials: MK
authors.lastname: Mikkelsen
authors.affiliation: Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, CA, USA.
authors.forename: Kamyar
authors.initials: K
authors.lastname: Kalantar-Zadeh
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN, USA; Division of Nephrology, Memphis Veteran Affairs Medical Center, Memphis, TN, USA. Electronic address: csaba.kovesdy@va.gov.
authors.forename: Csaba P
authors.initials: CP
authors.lastname: Kovesdy
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015331:Cohort Studies; D003920:Diabetes Mellitus / Q000503:physiopathology; D006801:Humans; D007668:Kidney / Q000502:physiology*; D007674:Kidney Diseases / Q000150:complications / Q000453:epidemiology*; D007677:Kidney Function Tests; D016015:Logistic Models; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D016016:Proportional Hazards Models