Duration of undiagnosed diabetes shorter than thought
medwireNews: Calculating the duration of undiagnosed diabetes from the presence of retinopathy using standard criteria produces overinflated estimates, say researchers.
Their findings, published in Diabetes Care, suggest the actual duration could be about half that of previously published estimates.
Massimo Porta and colleagues from the University of Turin in Italy, used a cohort of 12,074 patients with diabetes and stratified them according to age at onset (cutoff at 30 years) and whether they were receiving insulin treatment. They also grouped them by the presence of any retinopathy, which can appear in people without diabetes, or at least moderate retinopathy (cutoff at Early Treatment of Diabetic Retinopathy Study level of 20).
This revealed that the association between known diabetes duration and the presence of retinopathy was not always best explained by a linear model, as previously assumed. A linear model was the best fit only for the associations between any retinopathy and older-onset, insulin-treated diabetes and between moderate retinopathy and older-onset, non-insulin-treated diabetes. Other associations were better explained by quadratic or logistic models.
Using these models, the team calculated that moderate retinopathy first appeared in the older-onset, non-insulin-treated group (ie, definite Type 2 diabetes) an average of 2.66 years before diabetes was diagnosed. In the younger-onset, insulin-treated group (ie, Type 1 diabetes, with known onset time), it appeared an average of 3.29 years after onset, or 1.73 years when restricted to those with onset after puberty, which is thought to delay retinopathy.
Based on the findings in the younger-onset group, Porta et al calculated that patients in the older-onset group had a duration of undiagnosed diabetes lasting an average of 5.95 years, or 4.39 years if based on data from post-puberty onset.
This estimate of 4–6 years is much shorter than previous calculations that put the duration of undiagnosed diabetes at more than 10 years, say the researchers.
“That about 15% of the adult population may suffer from impaired glucose regulation without having full-blown type 2 diabetes and that impaired glucose tolerance is associated with increased risk for [diabetic retinopathy] suggest that part of those ‘hidden’ years may be spent in a prediabetic state, accounting at least in part for delayed and incomplete diagnoses of diabetes”, they write in Diabetes Care.
“Sorting out these issues will provide a more solid basis upon which to determine the feasibility of and opportunity for screening programs for the early detection of type 2 diabetes.”
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By Eleanor McDermid, Senior medwireNews Reporter