Cataract in type 2 diabetes mellitus in Isfahan, Iran: incidence and risk factors.
BACKGROUND
Evidence on the incidence of and risk factors for cataract in type 2 diabetes mellitus is scarce and mainly derived from studies in developed countries. Locally derived evidence is required for planning a well co-ordinated approach to this public health problem in developing countries.


OBJECTIVE
The objective of the present study was to estimate the incidence of and risk factors for the development of cataract in type 2 (insulin-treated and non-insulin-treated) diabetes using routinely collected data from a clinical information system at Isfahan Endocrinology and Metabolism Research Center, Iran.


METHODS
During the mean (standard deviation (SD)) follow-up period of 3.6 (2.7) (range 1-11) years, 3888 diabetic patients (1348 male and 2540 female) from Isfahan Endocrinology and Metabolism Research Center outpatient clinics have been examined. The mean (SD) age of the participants was 52.0 (10.5) years with a mean (SD) duration of diabetes of 12.6 (7.5) years at initial registration.


RESULTS
Among the 3888 patients who were free of cataract at initial registration with at least one follow-up visit between 1992 and 2004, the incidence of cataract was 33.1 (95% confidence interval (CI): 30.2, 36.1) (64.8 (95% CI: 57.7, 72.0) in males and 17.9 (95% CI: 15.2, 20.5) in females per 1000 person-years based on 14012 person-years of follow-up. The age-adjusted incidence rate of cataract was 20% greater among insulin-treated than non-insulin-treated type 2 diabetes mellitus clinic attenders and it increased with age. Using a Cox's Proportional Hazards Model for insulin and non-insulin-treated type 2 diabetes separately, age, age at diagnosis of diabetes, duration of diabetes, and smoking were significant predictors of cataract for insulin and non-insulin-treated type 2 diabetes patients. When all variables were entered in the model, fasting blood glucose and insulin treatment were significant predictors of cataract. In the insulin-treated group, fasting blood glucose was a significant predictor of cataract. Systolic and diastolic blood pressure, gender, HbA(1), proteinuria, body mass index, cholesterol, triglyceride and creatinine had no significant independent association with cataract when other covariates were considered.


CONCLUSIONS
These data suggest that cataract in this population of Iranian type 2 diabetic patients is common. With an estimated incidence of 33.1 per 1000 person-years of observation after mean 3.6 years' follow-up, diabetic cataract clearly poses a formidable health threat to Iranian diabetic patients. The results of this study highlight the need for regular eye examination in people with diabetes.
Janghorbani
Mohsen
M
Department of Epidemiology Isfahan Endocrinology & Metabolism Research Center, Isfahan University of Medical Sciences and Health Services Isfahan Iran. janghorbani@yahoo.com
Amini
Masoud
M
D017677:Age Distribution; D017668:Age of Onset; D002386:Cataract / Q000150:complications* / Q000453:epidemiology*; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012307:Risk Factors; D017678:Sex Distribution