title: Blue eyes as a risk factor for type 1 diabetes.
abstract: BACKGROUND
  A high frequency of blue eyes and fair skin are reported in northern European Caucasians with type 1 diabetes (T1D). Also there is an inverse relationship between latitude and T1D incidence. We determined whether iris colour and skin pigmentation are risk factors in a Caucasian population living in two Mediterranean regions located at the same latitude with higher ultraviolet B irradiance, but with different T1D incidence.
  
  
  METHODS
  We studied iris colour in 281 consecutive subjects with T1D and 298 controls. Skin type was evaluated by melanin quantification.
  
  
  RESULTS
  In Lazio, blue eyes and fair skin type are significantly more common in T1D subjects than in controls (21 versus 9%, p = 0.002; 50 versus 35%, p < 0.001, respectively). In Sardinia, the frequency of blue eyes in T1D subjects is twice that in controls (5.8 versus 2.6% and significantly higher when compared to the expected calculated frequency in the entire population). By logistic regression analysis, only blue eyes are independent and significant predictors of T1D [odds ratio for blue eyes = 2.2; 95% confidence interval (1.1-4.4), p = 0.019].
  
  
  CONCLUSIONS
  As previously shown in a Caucasian population from northern Europe, blue eyes and a trend for fair skin increase the risk for T1D also in a Caucasian population born and residing in a Mediterranean region (Continental Italy). This finding may be relevant for explaining different T1D incidence as prevalence of blue eyes differ substantially between northern and southern European Caucasians.
authors.affiliation: Institute of Biochemistry and Clinical Biochemistry, Catholic University of Sacred Hearth, Rome, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Di Stasio
authors.forename: Daria
authors.initials: D
authors.lastname: Maggi
authors.forename: Enzo
authors.initials: E
authors.lastname: Berardesca
authors.forename: Georgiana Clare
authors.initials: GC
authors.lastname: Marulli
authors.forename: Carla
authors.initials: C
authors.lastname: Bizzarri
authors.forename: Angelo
authors.initials: A
authors.lastname: Lauria
authors.forename: Rosalba
authors.initials: R
authors.lastname: Portuesi
authors.forename: Maria Gisella
authors.initials: MG
authors.lastname: Cavallo
authors.forename: Francesco
authors.initials: F
authors.lastname: Costantino
authors.forename: Raffaella
authors.initials: R
authors.lastname: Buzzetti
authors.forename: Elisa
authors.initials: E
authors.lastname: Astorri
authors.forename: Dario
authors.initials: D
authors.lastname: Pitocco
authors.forename: Marco
authors.initials: M
authors.lastname: Songini
authors.forename: Paolo
authors.initials: P
authors.lastname: Pozzilli
mesh_terms: D000328:Adult; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics*; D005127:Eye Color / Q000235:genetics*; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D019083:Mediterranean Region; D012307:Risk Factors; D012880:Skin Pigmentation; D044465:White People / Q000235:genetics