title: Spatial epidemiology of dry eye disease: findings from South Korea.
abstract: BACKGROUND
  DED rate maps from diverse regions may allow us to understand world-wide spreading pattern of the disease. Only few studies compared the prevalence of DED between geographical regions in non-spatial context. Therefore, we examined the spatial epidemiological pattern of DED prevalence in South Korea using a nationally representative sample.
  
  
  METHODS
  We analyzed 16,431 Korean adults aged 30 years or older of the 5th Korea National Health and Nutrition Examination Survey. DED was defined as previously diagnosed by an ophthalmologist as well as symptoms experienced. Multiple logistic regression analysis was used to assess the spatial pattern in the prevalence of DED, and effects of environmental factors.
  
  
  RESULTS
  Among seven metropolitan cities and nine provinces, three metropolitan cities located in the southeast of Korea revealed the highest prevalence of DED. After adjusting for sex, age and survey year, people living in urban areas had higher risk of having DED. Adjusted odds ratio for having previously diagnosed DED was 1.677 (95% CI 1.299-2.166) for metropolitan cities and 1.580 (95% CI 1.215-2.055) for other cities compared to rural areas. Corresponding odds ratio for presenting DED symptoms was 1.388 (95% CI 1.090-1.766) for metropolitan cities and 1.271 (95% CI 0.999-1.617) for other cities. Lower humidity and longer sunshine duration were significantly associated with DED. Among air pollutants, SO2 was associated with DED, while NO2, O3, CO, and PM10 were not.
  
  
  CONCLUSIONS
  Our findings suggest that prevalence of DED can be affected by the degree of urbanization and environmental factors such as humidity and sunshine duration.
authors.forename: Sun-Bi
authors.initials: SB
authors.lastname: Um
authors.forename: Na Hyun
authors.initials: NH
authors.lastname: Kim
authors.forename: Hyung Keun
authors.initials: HK
authors.lastname: Lee
authors.forename: Jong Suk
authors.initials: JS
authors.lastname: Song
authors.affiliation: Department of Preventive Medicine, Yonsei University College of Medicine, 50-1Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. hckim@yuhs.ac.
authors.forename: Hyeon Chang
authors.initials: HC
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis; D015352:Dry Eye Syndromes / Q000175:diagnosis / Q000453:epidemiology*; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D062305:Geographic Mapping; D006801:Humans; D006813:Humidity / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys / Q000379:methods; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D062211:Spatio-Temporal Analysis; D013472:Sunlight / Q000009:adverse effects