title: Age at onset and the risk of proliferative retinopathy in type 1 diabetes.
abstract: OBJECTIVE
  Age at onset of type 1 diabetes influences the risk of microvascular complications. However, the long-term risk of proliferative retinopathy within the wide spectrum of age at onset of type 1 diabetes is less well known.
  
  
  METHODS
  A sample of 1,117 consecutively recruited patients was drawn from the FinnDiane Study population (4,800 patients). Type 1 diabetes was defined as age at onset <or=40 years, insulin treatment initiated within 1 year, and C-peptide <or=0.3 nmol/l. Retinopathy status was graded based on ophthalmic records and/or fundus photographs. The risk of proliferative retinopathy was studied in age-at-onset groups 0-4, 5-14, and 15-40 years.
  
  
  RESULTS
  The mean durations to proliferative retinopathy were 24.3 (22.7-25.9) years in the 0-4 years group, 20.1 (19.2-21.1) years in the 5-14 years group, and 21.6 (19.8-23.3) years in the 15-40 years group (P < 0.001). In a Cox regression model, with A1C, blood pressure, sex, and BMI as covariates, the highest risk of proliferative retinopathy was observed in the 5-14 years group (hazard ratio 1.90 [95% CI 1.45-2.48], P < 0.001). Diabetes onset 0-4 vs. 5-14 years made no difference in the long-term risk of proliferative retinopathy (P = 0.2). When split into two groups, age at onset <15 years was associated with a higher long-term risk than age at onset >or=15 years (1.82 [1.40-2.36], P < 0.001).
  
  
  CONCLUSIONS
  Age at onset significantly modifies the long-term risk of proliferative retinopathy. The highest risk is in age-at-onset group 5-14 years, whereas the lowest risk is in age-at-onset group 15-40 years.
authors.affiliation: Folkhälsan Institute of Genetics, Folkhälsan Research Center, Biomedicum Helsinki, Helsinki, Finland.
authors.forename: Kustaa
authors.initials: K
authors.lastname: Hietala
authors.forename: Valma
authors.initials: V
authors.lastname: Harjutsalo
authors.forename: Carol
authors.initials: C
authors.lastname: Forsblom
authors.forename: Paula
authors.initials: P
authors.lastname: Summanen
authors.forename: Per-Henrik
authors.initials: PH
authors.lastname: Groop
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000150:complications*; D003930:Diabetic Retinopathy / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult