title: Altitude and regional gradients in chronic kidney disease prevalence in Costa Rica: Data from the Costa Rican Longevity and Healthy Aging Study.
abstract: OBJECTIVE
  Recent studies in Central America indicate that mortality attributable to chronic kidney disease (CKD) is rising rapidly. We sought to determine the prevalence and regional variation of CKD and the relationship of biologic and socio-economic factors to CKD risk in the older-adult population of Costa Rica.
  
  
  METHODS
  We used data from the Costa Rican Longevity and Health Aging Study (CRELES). The cohort was comprised of 2657 adults born before 1946 in Costa Rica, chosen through a sampling algorithm to represent the national population of Costa Ricans >60 years of age. Participants answered questionnaire data and completed laboratory testing. The primary outcome of this study was CKD, defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2.
  
  
  RESULTS
  The estimated prevalence of CKD for older Costa Ricans was 20% (95% CI 18.5-21.9%). In multivariable logistic regression, older age (adjusted odds ratio [aOR] 1.08 per year, 95% CI 1.07-1.10, P < 0.001) was independently associated with CKD. For every 200 m above sea level of residence, subjects' odds of CKD increased 26% (aOR 1.26 95% CI 1.15-1.38, P < 0.001). There was large regional variation in adjusted CKD prevalence, highest in Limon (40%, 95% CI 30-50%) and Guanacaste (36%, 95% CI 26-46%) provinces. Regional and altitude effects remained robust after adjustment for socio-economic status.
  
  
  CONCLUSIONS
  We observed large regional and altitude-related variations in CKD prevalence in Costa Rica, not explained by the distribution of traditional CKD risk factors. More studies are needed to explore the potential association of geographic and environmental exposures with the risk of CKD.
authors.affiliation: Division of Nephrology, Department of Medicine, Drexel University College of Medicine, Philadelphia, PA, USA.
authors.forename: Meera N
authors.initials: MN
authors.lastname: Harhay
authors.affiliation: Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Harhay
authors.affiliation: Department of Geriatric Medicine, National Geriatrics and Gerontology Hospital, San José, Costa Rica.
authors.forename: Fernando
authors.initials: F
authors.lastname: Coto-Yglesias
authors.affiliation: Central American Population Center, University of Costa Rica, San José, Costa Rica.|Department of Demography, University of California, Berkeley, CA, USA.
authors.forename: Luis
authors.initials: L
authors.lastname: Rosero Bixby
keywords: Altitud; Altitude; Chronic kidney disease; Costa Rica; Enfermedad Renal Crónica; Enfermedad Tropical Crónica; Epidemiology; Epidemiología; Mesoamerican nephropathy; Nefropatía Mesoamericana; Tropical chronic disease; altitude; maladie chronique tropicale; maladie rénale chronique; néphropathie mésoaméricaine; épidémiologie