title: Age and cystatin C in healthy adults: a collaborative study.
abstract: BACKGROUND
  Kidney function declines with age, but a substantial portion of this decline has been attributed to the higher prevalence of risk factors for kidney disease at older ages. The effect of age on kidney function has not been well described in a healthy population across a wide age spectrum.
  
  
  METHODS
  The authors pooled individual-level cross-sectional data from 18 253 persons aged 28-100 years in four studies: the Cardiovascular Health Study; the Health, Aging and Body Composition Study; the Multi-Ethnic Study of Atherosclerosis and the Prevention of Renal and Vascular End-Stage Disease cohort. Kidney function was measured by cystatin C. Clinical risk factors for kidney disease included diabetes, hypertension, obesity, smoking, coronary heart disease, cerebrovascular disease, peripheral arterial disease and heart failure.
  
  
  RESULTS
  Across the age range, there was a strong, non-linear association of age with cystatin C concentration. This association was substantial, even among participants free of clinical risk factors for kidney disease; mean cystatin C levels were 46% higher in participants 80 and older compared with those <40 years (1.06 versus 0.72 mg/L, P < 0.001). Participants with one or more risk factors had higher cystatin C concentrations for a given age, and the age association was slightly stronger (P < 0.001 for age and risk factor interaction).
  
  
  CONCLUSIONS
  There is a strong, non-linear association of age with kidney function, even in healthy individuals. An important area for research will be to investigate the mechanisms that lead to deterioration of kidney function in apparently healthy persons.
authors.affiliation: Department of Epidemiology, School of Public Health, University of California, Berkeley, CA, USA. michelle.odden@ucsf.edu
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Odden
authors.forename: Ira B
authors.initials: IB
authors.lastname: Tager
authors.forename: Ron T
authors.initials: RT
authors.lastname: Gansevoort
authors.forename: Stephan J L
authors.initials: SJ
authors.lastname: Bakker
authors.forename: Ronit
authors.initials: R
authors.lastname: Katz
authors.forename: Linda F
authors.initials: LF
authors.lastname: Fried
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.forename: Robert B
authors.initials: RB
authors.lastname: Canada
authors.forename: Tamara
authors.initials: T
authors.lastname: Harris
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Sarnak
authors.forename: David
authors.initials: D
authors.lastname: Siscovick
authors.forename: Michael G
authors.initials: MG
authors.lastname: Shlipak
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D006801:Humans; D007668:Kidney / Q000502:physiology*; D008875:Middle Aged; D012016:Reference Values
chemical_list: D055316:Cystatin C