title: The epidemiological association of altitude with chronic kidney disease: Evidence of protective effect.
abstract: OBJECTIVE
  We sought to determine the association between living at high altitudes and the estimated glomerular filtration rate (eGFR) and also to determine the prevalence of end-stage renal disease (ESRD) at various altitudes.
  
  
  METHODS
  In the first part of the study, we used data from the National Health and Nutrition Examination Survey III to examine the association between altitude of residence and eGFR. In the second part, we used the United States Renal Data System to study the association between altitude and prevalence of ESRD. The query revealed an ESRD prevalence of 485,012 for the year 2005. The prevalence rates were merged with the zip codes dataset.
  
  
  RESULTS
  The mean eGFR was significantly increased at higher altitudes (78.4 ± 21.6 vs 85.4 ± 26.8 mL/min for categories 1 and 5, respectively; P < 0.05). In the analysis of the United States Renal Data System data for prevalence of ESRD, we found a significantly lower prevalence at the altitude of 523 feet and higher.
  
  
  CONCLUSIONS
  Using a population-based approach, our study demonstrates an association between altitude and renal function. This association is independent of all factors studied and is reached at approximately 250 feet. There is also a negative association between the prevalence of ESRD and altitude of residence. Further studies are needed to elucidate the pathophysiological basis of these epidemiological findings.
authors.affiliation: Pennsylvania State University College of Medicine, Hershey Medical Center, Harrisburg, Pennsylvania, USA. nghahramani@hmc.psu.edu
authors.forename: Nasrollah
authors.initials: N
authors.lastname: Ghahramani
authors.forename: Faris
authors.initials: F
authors.lastname: Ahmed
authors.forename: Ammar
authors.initials: A
authors.lastname: Al-Laham
authors.forename: Eugene J
authors.initials: EJ
authors.lastname: Lengerich
mesh_terms: D000531:Altitude; D016208:Databases, Factual; D005260:Female; D005919:Glomerular Filtration Rate; D006306:Health Surveys; D006801:Humans; D007668:Kidney / Q000502:physiology; D007676:Kidney Failure, Chronic / Q000453:epidemiology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015995:Prevalence