Familial clustering of diabetic retinopathy in South Indian Type 2 diabetic patients.
OBJECTIVE
The aim of the study was to determine whether there is familial clustering of diabetic retinopathy among South Indian Type 2 diabetic subjects.


METHODS
During the period September 1991 to September 1997, 322 families with at least two diabetic siblings who were registered at our centre and had undergone a retinal examination were selected for the study. The sibling with the longest duration of diabetes was defined as the proband. The prevalence of retinopathy was compared between the siblings of probands with and without retinopathy.


RESULTS
Diabetic retinopathy was diagnosed in 11.2% of the siblings of the probands without diabetic retinopathy and in 35.3% of the siblings of the probands with diabetic retinopathy (P < 0.0001). The increased prevalence of retinopathy among siblings of probands with retinopathy represented all grades of retinopathy, namely non-proliferative diabetic retinopathy with and without maculopathy and proliferative diabetic retinopathy, although the latter did not reach statistical significance due to the small numbers. Hypertension, metabolic control and the duration of diabetes among the probands did not affect the clustering of retinopathy. The odds ratio for retinopathy in the siblings of probands with retinopathy after adjusting for age, glycosylated haemoglobin, duration of diabetes, proteinuria and other confounding variables was 3.37(95% confidence interval 1.56-7.29, P = 0.002).


CONCLUSIONS
Familial clustering of diabetic retinopathy was three times higher in siblings of Type 2 diabetic subjects with diabetic retinopathy.
Rema
M
M
Madras Diabetes Research Foundation and M V Diabetes Specialities Centre, Gopalapuram, Chennai, India. drrema@vsnl.com
Saravanan
G
G
Deepa
R
R
Mohan
V
V
D000328:Adult; D017668:Age of Onset; D016000:Cluster Analysis; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000235:genetics*; D003925:Diabetic Angiopathies / Q000453:epidemiology / Q000235:genetics; D003930:Diabetic Retinopathy / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D006973:Hypertension / Q000453:epidemiology / Q000235:genetics; D007194:India / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D015995:Prevalence; D012044:Regression Analysis