Higher age at onset of type 1 diabetes increases risk of macular oedema.

PURPOSE

To investigate whether age at onset of type 1 diabetes is a risk factor for clinically significant macular oedema (CSME).

METHODS

A sample of 1354 patients with a mean duration of diabetes 24.6 ± 11.6 years was drawn from the FinnDiane Study population and divided into age at onset groups 0-4 (n = 184), 5-14 (n = 662) and 15-40 years (n = 508). Type 1 diabetes was defined as age at onset ≤40 years, C-peptide negativity and insulin treatment initiated within 1 year of diagnosis. Retinopathy status was assessed from fundus photographs and stereoscopic fundus examinations and graded with the ETDRS scale.

RESULTS

After 30 years of diabetes, the estimated cumulative incidences of CSME were 17% (95% CI 11-26) in age at onset group 0-4 years, 27% (95% CI 23-32) in age at onset group 5-14 years and 34% (95% CI 27-41) in age at onset group 15-40 years (p = 0.002, Gray's test). In a competing risks regression model, adjusted for covariates selected with Bayesian information criteria, age at onset 5-14 years (HR 1.89 [95% CI 1.22-2.91], p = 0.004), and age at onset 15-40 years (HR 3.72 [95% CI 2.35-5.89], p < 0.0001), were significant overall risk factors for CSME (p < 0.0001). Higher ETDRS score (HR 1.04 ([95% CI 1.03-1.05], p < 0.0001), HbA1c (HR 1.12 [95% CI 1.02-1.23], p = 0.016), and total cholesterol (HR 1.19 [95% CI 1.04-1.37], p = 0.013) also increased the risk of CSME.

CONCLUSIONS

Higher age at onset of type 1 diabetes is a significant risk factor for macular oedema. This suggests that ageing may modify the risk of retinopathy in type 1 diabetes.