title: Association between obesity and glomerular hyperfiltration: the confounding effect of smoking and sodium and protein intakes.
abstract: OBJECTIVE
  Glomerular hyperfiltration has been suggested as a possible mechanism linking obesity and chronic kidney disease (CKD), independently of classical risk factors. We explored the association of overweight and obesity with glomerular hyperfiltration in a large sample of the Swiss adult population, accounting for several confounders including dietary factors.
  
  
  METHODS
  Data from a 2010 to 2012 cross-sectional population-based survey in Switzerland were used. Creatinine clearance (CrCl) was determined from 24-h urine collection; CrCl > 140 ml/min was used to define glomerular hyperfiltration. Participants were categorized into lean (<25 kg/m(2)), overweight (25-29.9 kg/m(2)) and obese (≥30 kg/m(2)) according to body mass index (BMI).
  
  
  RESULTS
  A total of 1339 participants were included in the analysis [median (IQR) age 49.4 (34.3-63.5) years, 48.9 % men]. The prevalences of overweight and obesity were 32.2 and 14.2 %, respectively. Median CrCl was 102[84-121] ml/min in lean, 110 [87-136] ml/min in overweight and 124 [97-150] ml/min in obese participants (p < 0.001). The prevalence of glomerular hyperfiltration increased across BMI categories (10.4, 20.8 and 34.7 %, respectively; p < 0.001). This positive association remained significant after adjusting for age, sex, hypertension, diabetes, smoking and dietary factors (sodium and protein intakes): odds ratio [95 %CI] 2.39 [1.52-3.76] (p < 0.001) for overweight versus lean and 4.10[2.31-7.27] (p < 0.001) for obesity versus lean.
  
  
  CONCLUSIONS
  BMI categories and glomerular hyperfiltration are positively associated, independently of other known CKD risk factors and dietary confounders, suggesting that glomerular hyperfiltration may represent an early renal phenotype in obesity. Our observations confirm the significant association of glomerular hyperfiltration with sodium and protein intakes and identify sodium intake as an important modifying factor of the association between hyperfiltration and obesity.
authors.affiliation: Department of Internal Medicine and Nephrology, Locarno Hospital, 6600, Locarno, Switzerland. adam.ogna@chuv.ch.
authors.forename: Adam
authors.initials: A
authors.lastname: Ogna
authors.affiliation: Service of Nephrology and Hypertension, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Valentina
authors.initials: V
authors.lastname: Forni Ogna
authors.affiliation: Community Prevention Unit, University Institute of Social and Preventive Medicine (IUMSP), Lausanne, Switzerland.
authors.forename: Murielle
authors.initials: M
authors.lastname: Bochud
authors.affiliation: Community Prevention Unit, University Institute of Social and Preventive Medicine (IUMSP), Lausanne, Switzerland.|Unit of Population Epidemiology, Geneva University Hospitals, Geneva, Switzerland.
authors.forename: Idris
authors.initials: I
authors.lastname: Guessous
authors.affiliation: Community Prevention Unit, University Institute of Social and Preventive Medicine (IUMSP), Lausanne, Switzerland.
authors.forename: Fred
authors.initials: F
authors.lastname: Paccaud
authors.affiliation: Service of Nephrology and Hypertension, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Burnier
authors.affiliation: Service of Nephrology and Hypertension, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Gregoire
authors.initials: G
authors.lastname: Wuerzner
mesh_terms: D000328:Adult; D015992:Body Mass Index; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D004044:Dietary Proteins / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology; D007674:Kidney Diseases / Q000150:complications / Q000453:epidemiology* / Q000652:urine; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology* / Q000652:urine; D050177:Overweight / Q000150:complications / Q000453:epidemiology* / Q000652:urine; D015995:Prevalence; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000009:adverse effects*; D013557:Switzerland
chemical_list: D004044:Dietary Proteins; D012982:Sodium, Dietary; D003404:Creatinine
keywords: Dietary factors; Glomerular hyperfiltration; Kidney disease; Obesity; Overweight