title: Geographic and climatic factors associated with exfoliation syndrome.
abstract: OBJECTIVE
  To identify geographic and climatic risk factors associated with exfoliation syndrome (ES).
  
  
  METHODS
  A retrospective study of 626 901 eye care recipients, dating from 2001 to 2007 from 47 US states in a managed care network. Incident ES cases-patients (N = 3367) were identified by using billing codes. We assessed the risk of ES by geographic latitude tier in the continental United States and assigned state-level climatic data (eg, ambient temperature, elevation, and sun exposure) according to patients' residential location. The hazard of ES was calculated by using multivariable-adjusted Cox proportional hazards regression models.
  
  
  RESULTS
  Compared with middle-tier residence, northern-tier residence (above 42°N) was associated with an increased hazard of ES (adjusted hazard ratio [HR], 2.14; 95% confidence interval [CI], 1.94-2.35). Southern-tier (below 37°N) was associated with a reduced hazard of ES (HR, 0.83; 95% CI, 0.75-0.93). Excluding whites did not change these associations. After adjustment for joint environmental effects, for every 1° increase in July high temperature, the hazard of ES decreased by 9% (HR, 0.91; 95% CI, 0.89-0.93); for every 1° increase in January low temperature, the hazard decreased 3% (0.97; 0.96-0.98). For each additional sunny day annually, the hazard increased by 1.5% (HR, 1.02; 95% CI, 1.01-1.02) in locations with average levels of other climatic factors.
  
  
  CONCLUSIONS
  Ambient temperature and sun exposure may be important environmental triggers of ES.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, 48105, USA. jdstein@med.umich.edu
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Stein
authors.forename: Louis R
authors.initials: LR
authors.lastname: Pasquale
authors.forename: Nidhi
authors.initials: N
authors.lastname: Talwar
authors.forename: Denise S
authors.initials: DS
authors.lastname: Kim
authors.forename: David M
authors.initials: DM
authors.lastname: Reed
authors.forename: Bin
authors.initials: B
authors.lastname: Nan
authors.forename: Jae Hee
authors.initials: JH
authors.lastname: Kang
authors.forename: Janey L
authors.initials: JL
authors.lastname: Wiggs
authors.forename: Julia E
authors.initials: JE
authors.lastname: Richards
mesh_terms: D000368:Aged; D002980:Climate; D017889:Exfoliation Syndrome / Q000453:epidemiology*; D005260:Female; D005843:Geography; D005902:Glaucoma, Open-Angle / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology