Objectives: Several cross-sectional studies have reported on the prevalence of diabetes in India. However, there are virtually no longitudinal population-based studies on the incidence of diabetes from India. The aim of the study was to determine the incidence of diabetes and prediabetes in an urban south Indian population.
Methods: The Chennai Urban Population Study [CUPS], an ongoing epidemiological study in two residential colonies in Chennai [the largest city in southern India, formerly called Madras] was launched in 1996; the baseline study was completed in 1997. Follow-up examination was performed after a mean period of 8 years. At follow-up, 501 [47.0%] subjects had moved out of this colonies and were lost to follow-up. Of the remaining 564 individuals, 513 [90.9%] provided blood samples for biochemical analysis. Regression analysis was done using incident diabetes as dependant variable to identify factors associated with development of diabetes or pre-diabetes.
Results: Among subjects with normal glucose tolerance (NGT) at baseline [n=476], 64 (13.4%) developed diabetes and 48 (10.1%) developed pre-diabetes (IGT or IFG). The incidence rate of diabetes was 20.2 per 1000 person years and that of pre-diabetes was 13.1 per 1000 person years among subjects with NGT. Of the 37 individuals who were pre-diabetic at baseline, 15 (40.5%) developed diabetes [incidence rate: 64.8 per 1000 person years], 16 (43.2%) remained as pre-diabetic and 6 (16.2%) reverted to normal during the follow-up period. Regression analysis revealed obesity [Odds Ratio (OR): 2.1, p=0.001], abdominal obesity [OR: 2.23, p<0.001] and hypertension [OR: 2.57, p<0.001] to be significantly associated with incident diabetes. The Indian Diabetes Risk Score (IDRS) showed the strongest association with incident diabetes [OR: 5.14, p<0.001].
Conclusion: The study shows that the incidence of diabetes is very high among urban south Indians. While obesity, abdominal obesity and hypertension were associated with incident diabetes, IDRS was the strongest predictor of incident of diabetes in this population.