title: Exfoliation syndrome: frequency, gender distribution and association with climatically induced alterations of the cornea and conjunctiva.
abstract: OBJECTIVE
  To investigate exfoliation syndrome (ES) in order to elucidate gender distribution and the roles of genetic and climatic factors in its manifestation.
  
  
  METHODS
  We studied the gender distribution of ES and the association between ES and the appearance of certain climatically induced disorders (pterygium, climatic droplet keratopathy) and the size of pingueculae in populations living in the Arctic region, in temperate regions and in tropical regions. This involved a total of 11 samples taken in eight different countries, comprising 2206 persons of both genders over the age of 50 years.
  
  
  RESULTS
  A total of 1051 males were investigated for ES and 147 of them (14.0%) were found to have it. The corresponding figures for females were 1093 and 177 (16.2%). After standardization according to age, no systematic difference between the genders was found in the study. The frequency of ES varied greatly. It was not observed at all in the Inuit (Eskimos) but was found most frequently (about 30%) among the Saami (Lapps), Aland Islanders, Finns, Icelanders and Russians over 70 years of age. After the age of 50, the frequency of ES increases rapidly with age in all populations. However, the curves for ES in people living in the tropics show a delay of about 10 years. In contrast, the frequency of climatically caused changes (pterygium, climatic keratopathy and pronounced pinguecula) mostly peaks at the age of 50 years and is highest in the tropics and in the Arctic. Males in these regions tended to be more affected by climatically caused changes than females. Likewise, in tropical climates, where radiation from the sun is strong, and in Lapland and Novosibirsk, where there is radiation from snow, males showed more evidence of ES than females. However, examination of 506 patients from a private practice in South Finland, who were under observation for glaucoma or for risk of glaucoma, showed females to be in the majority of those with ES.
  
  
  CONCLUSIONS
  As a rule, climate does not appear to influence the occurrence of ES. However, in tropical countries, where radiation from the sun is strong, ES was more common among males than among females. In the light of its peculiar population distribution, even when climatic factors are considered, there would appear to be an important genetic factor involved in the manifestation of ES.
authors.affiliation: Folkhälsan Institute of Genetics, Population Genetics Unit, Helsinki, Finland.
authors.forename: Henrik
authors.initials: H
authors.lastname: Forsius
authors.forename: Eva
authors.initials: E
authors.lastname: Forsman
authors.forename: Johan
authors.initials: J
authors.lastname: Fellman
authors.forename: Aldur W
authors.initials: AW
authors.lastname: Eriksson
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002980:Climate; D003229:Conjunctival Diseases / Q000209:etiology*; D003316:Corneal Diseases / Q000209:etiology*; D004781:Environmental Exposure / Q000009:adverse effects*; D017889:Exfoliation Syndrome / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D005260:Female; D005828:Genetics, Population; D005843:Geography; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011625:Pterygium / Q000209:etiology*; D017678:Sex Distribution