title: Pterygium in an aged Mongolian population: a population-based study in China.
abstract: OBJECTIVE
  To determine the prevalence and identify associated risk factors for pterygium in an elderly Mongolian population at high altitude in Henan County, China.
  
  
  METHODS
  A population-based survey was conducted from June 2006 to September 2006. A stratified, clustered, random sampling procedure was used to select 2486 Mongolian people aged 40 years and older. Pterygium was diagnosed and graded clinically as grade 1 (transparent), 2 (intermediate), and 3 (opaque). Risk factors associated with pterygium were evaluated with logistic regression models.
  
  
  RESULTS
  From 2486 eligible subjects, 2112 (84.9%) were examined. There were 378 people with either unilateral (n=228) or bilateral (n=150) pterygia, equivalent to an overall prevalence of 17.9% (95% confidence interval (CI) 16.3, 19.5). The prevalence increased with older age (chi (2)-test of trend P<0.001). Visual acuity decreased with higher group of pterygium (chi (2)=97.759, P<0.0001). Pterygium was independently associated with Schirmer's test (< or =5 mm) (odds ratio (OR) 2.4; 95% CI, 1.9, 3.1), tear breakup time (< or =10 s) (OR 2.3; 95% CI, 1.8, 2.9), lower education level (<3 years) (OR 2.1; 95% CI, 1.4, 3.2), increasing age (OR 2.0; 95% CI, 1.4, 2.8) for persons 70-79, compared with 40-49, and other risk factors.
  
  
  CONCLUSIONS
  The prevalence of pterygium in an older Mongolian population at high altitude is high, primarily because of ocular sun exposure and the other effects of the unique plateau climate, and representing an important health problem. People should be strongly encouraged to wear a wide-brimmed hat and/or sunglasses whenever they are outside.
authors.affiliation: Institute of Developmental Biology, Lanzhou University, China.
authors.forename: J
authors.initials: J
authors.lastname: Lu
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: P
authors.initials: P
authors.lastname: Lu
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: K
authors.initials: K
authors.lastname: Shi
authors.forename: Y
authors.initials: Y
authors.lastname: Kang
authors.forename: L
authors.initials: L
authors.lastname: Ke
authors.forename: R
authors.initials: R
authors.lastname: Chen
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000531:Altitude; D002681:China / Q000453:epidemiology; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008986:Mongolia / Q000208:ethnology; D011625:Pterygium / Q000208:ethnology* / Q000209:etiology / Q000517:prevention & control; D011832:Radiation Injuries / Q000208:ethnology / Q000209:etiology; D017678:Sex Distribution; D012959:Socioeconomic Factors; D013472:Sunlight / Q000009:adverse effects; D014792:Visual Acuity