Diabetes: How Long from Onset to Retinopathy?

Massimo Porta, MD PhD Professor of Medicine Head, Unit of Internal Medicine 1 Department of Medical Sciences  University of TurinMedicalResearch.com Interview with:
Massimo Porta, MD PhD
Professor of Medicine Head, Unit of Internal Medicine 1
Department of Medical Sciences  University of Turin

MedicalResearch.com: What are the main findings of the study?

Dr. Porta: Type 2 diabetes has a slow, insidious onset and may remain undiagnosed for several years, during which complications may arise and progress. As a result, many patients already have retinopathy at the time a clinical diagnosis is finally made. Previous attempts at estimating the duration of this period of “hidden” diabetes relied upon  extrapolations of a linear correlation between known duration of diabetes and prevalence of retinopathy.

This led to overestimates, because:

a) the best fitting correlation may not be linear,
b) series included insulin treated patients, who might have late-onset type 1 diabetes,
c) patients with any mild retinopathy were included whereas we now know that up to 10% of non diabetic individuals may have minimal retinal signs.

By taking these variables into account, ie including only patients not on insulin and with moderate or more severe retinopathy and applying different mathematical models, we ended up with an estimated duration preceding diagnosis of type 2 diabetes of 4-6 years, against longer than 13 years using “standard” criteria.

MedicalResearch.com: Were any of the findings unexpected?

Dr. Porta: Whereas we expected that the above corrections would somehow modify the estimated length of “hidden” diabetes, the magnitude of the above difference was somehow unexpected.

MedicalResearch.com: What should clinicians and patients take away from your report?

Dr. Porta: Perhaps reassuring is the suggestion that diabetes may be overlooked less that feared from previous reports. However, that is no reason to be off guard.
A suggestion that comes out of this study is that, whatever disturbance of carbohydrate metabolism leads to developing retinopathy, it may not coincide with current criteria for diagnosis of type 2 diabetes. Part of the years preceding diagnosis might be spent in what we consider today a prediabetic state (impaired fasting glucose, impaired glucose tolerance, or others yet to be defined).

MedicalResearch.com:What recommendations do you have for future research as a result of this study?

Dr. Porta: One needs to better understand if a threshold really exists above which the risk starts to arise to develop not just isolated mild retinal lesions but proper diabetic retinopathy.

Citation:

Estimating the Delay Between Onset and Diagnosis of Type 2 Diabetes From the Time Course of Retinopathy Prevalence

Massimo Porta, Giulia Curletto, Dario Cipullo, Roberta Rigault de la Longrais, Marina Trento, Pietro Passera, Anna Viola Taulaigo, Sabrina Di Miceli, Antonella Cenci, Paola Dalmasso, and Franco Cavallo

Diabetes Care published ahead of print April 4, 2014, doi:10.2337/dc13-2101 1935-5548