title: Prevalence, clinical profile, iron status, and subject-specific traits for excessive erythrocytosis in andean adults living permanently at 3,825 meters above sea level.
abstract: BACKGROUND
  Excessive erythrocytosis (EE) is a prevalent condition in populations living at high altitudes (> 2,500 m above sea level). Few large population-based studies have explored the association between EE and multiple subject-specific traits including oxygen saturation, iron status indicators, and pulmonary function.
  
  
  METHODS
  We enrolled a sex-stratified and age-stratified sample of 1,065 high-altitude residents aged ≥ 35 years from Puno, Peru (3,825 m above sea level) and conducted a standardized questionnaire and physical examination that included spirometry, pulse oximetry, and a blood sample for multiple clinical markers. Our primary objectives were to estimate the prevalence of EE, characterize the clinical profile and iron status indicators of subjects with EE, and describe subject-specific traits associated with EE.
  
  
  RESULTS
  Overall prevalence of EE was 4.5% (95% CI, 3.3%-6.0%). Oxygen saturation was significantly lower among EE than non-EE group subjects (85.3% vs 90.1%, P < .001) but no difference was found in iron status indicators between both groups (P > .09 for all values). In multivariable logistic regression, we found that age ≥ 65 years (OR = 2.45, 95% CI, 1.16-5.09), male sex (3.86, 1.78-9.08), having metabolic syndrome (2.66, 1.27-5.75) or being overweight (5.20, 1.95-16.77), pulse oximetry < 85% (14.90, 6.43-34.90), and % predicted FVC < 80% (13.62, 4.40-41.80) were strongly associated with EE. Attributable fractions for EE were greatest for being overweight (26.7%), followed by male sex (21.5%), pulse oximetry < 85% (16.4%), having metabolic syndrome (14.4%), and % predicted FVC < 80% (9.3%).
  
  
  CONCLUSIONS
  We found a lower prevalence of EE than in previous reports in the Peruvian Andes. Although the presence of hypoxemia and decreased vital capacity were strongly associated with excessive erythrocytosis, being overweight or having metabolic syndrome were associated with an important fraction of cases in our study population.
authors.affiliation: From the Division of Pulmonary and Critical Care, School of Medicine, Johns Hopkins University, Baltimore, MD.
authors.forename: Aldo
authors.initials: A
authors.lastname: De Ferrari
authors.affiliation: CRONICAS Centre of Excellence for Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru; Departamento de Medicina, Escuela de Medicina, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: J Jaime
authors.initials: JJ
authors.lastname: Miranda
authors.affiliation: CRONICAS Centre of Excellence for Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru; Departamento de Medicina, Escuela de Medicina, Universidad Peruana Cayetano Heredia, Lima, Peru; Program in Global Disease Epidemiology and Control, Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.affiliation: Cardiovascular Imaging and Clinical Research Core Laboratory, Cardiovascular Division, School of Medicine, Washington University in St. Louis, St. Louis, MO.
authors.forename: Victor G
authors.initials: VG
authors.lastname: Dávila-Román
authors.affiliation: Departamento de Ciencias Biológicas y Fisiológicas, Laboratorio de Adaptación a la Altura, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Fabiola
authors.initials: F
authors.lastname: León-Velarde
authors.affiliation: Departamento de Ciencias Biológicas y Fisiológicas, Laboratorio de Adaptación a la Altura, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Maria
authors.initials: M
authors.lastname: Rivera-Ch
authors.affiliation: Departamento de Ciencias Biológicas y Fisiológicas, Laboratorio de Adaptación a la Altura, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Luis
authors.initials: L
authors.lastname: Huicho
authors.affiliation: CRONICAS Centre of Excellence for Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Antonio
authors.initials: A
authors.lastname: Bernabé-Ortiz
authors.affiliation: From the Division of Pulmonary and Critical Care, School of Medicine, Johns Hopkins University, Baltimore, MD.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wise
authors.affiliation: From the Division of Pulmonary and Critical Care, School of Medicine, Johns Hopkins University, Baltimore, MD; CRONICAS Centre of Excellence for Chronic Diseases, Universidad Peruana Cayetano Heredia, Lima, Peru; Departamento de Medicina, Escuela de Medicina, Universidad Peruana Cayetano Heredia, Lima, Peru. Electronic address: wcheckl1@jhmi.edu.
authors.forename: William
authors.initials: W
authors.lastname: Checkley
mesh_terms: D000328:Adult; D000368:Aged; D000531:Altitude; D005006:Ethnicity; D005260:Female; D006801:Humans; D007501:Iron / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010568:Peru / Q000453:epidemiology; D011086:Polycythemia / Q000097:blood / Q000208:ethnology*; D015995:Prevalence; D012016:Reference Values
chemical_list: D007501:Iron