The risk of proliferative retinopathy in siblings with Type 1 diabetes

Authors

  • K. Hietala,

    1. Folkhälsan Institute of Genetics, Folkhälsan Research Centre, Biomedicum Helsinki
    2. Department of Ophthalmology, Helsinki University Central Hospital
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  • C. Forsblom,

    1. Folkhälsan Institute of Genetics, Folkhälsan Research Centre, Biomedicum Helsinki
    2. Division of Nephrology, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland
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  • P. Summanen,

    1. Department of Ophthalmology, Helsinki University Central Hospital
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  • P.-H. Groop,

    1. Folkhälsan Institute of Genetics, Folkhälsan Research Centre, Biomedicum Helsinki
    2. Division of Nephrology, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland
    3. The Baker IDI Heart and Diabetes Institute, Melbourne, Vic., Australia
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  • on behalf of the FinnDiane Study Group


Per-Henrik Groop. E-mail: per-henrik.groop@helsinki.fi

Abstract

Diabet. Med. 29, 1567–1573 (2012)

Abstract

Aims  The siblings first affected by Type 1 diabetes (probands) within a sibship have been shown to have a lower age at onset of Type 1 diabetes compared with their later-affected siblings. The aim of the present study was to investigate whether this difference affects the long-term risk of proliferative diabetic retinopathy.

Methods  A cohort of 396 siblings with Type 1 diabetes in 188 sibships was drawn from a larger Finnish Diabetic Nephropathy Study population (4800 patients). Ophthalmic records were obtained for 369/396 (93%) patients. Retinopathy was graded based on fundus photographs and/or repeated ophthalmoscopies.

Results  The median age at onset of Type 1 diabetes was 8.4 (interquartile range 4.2–13.3) years in probands and 16.9 (interquartile range 10.2–27.8) years in later-affected siblings (P < 0.001). Proliferative retinopathy was diagnosed in 115/369 (31%) patients. The cumulative incidence estimates for proliferative retinopathy, accounting for the competing risk of death, were 21% (95% CI 15–27) in probands and 26% (95% CI 19–35) in later-affected siblings at 20 years of diabetes duration, and the respective 30 years’ incidences were 37% (95% CI 29–45) and 53% (95% CI 40–64), (P = 0.05, Gray’s test). The risk of proliferative retinopathy, adjusted for conventional risk factors, age at onset and sibship size, was higher in later-affected siblings [hazard ratio 1.75 (95% CI 1.13–2.75), P = 0.01] compared with their probands.

Conclusion  The siblings first affected by Type 1 diabetes had a better long-term prognosis with regards to development of proliferative retinopathy compared with their later-affected siblings.

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