BACKGROUND: Circulating antibodies to glutamic acid decarboxylase (GADab) and tyrosine phosphatase-like molecule IA-2 (IA-2ab) are major indicators for auto-immune destruction of pancreatic islet cells. They identify a majority of Caucasians with type 1 diabetes and approximately 50% of Asians, providing evidence of an idiopathic aetiology in the latter. The present study investigated these autoantibodies in a mixed ethnic group.
METHODS: Hospital clinic patients with clinically defined type 1 (n = 93) and type 2 (n = 300) diabetes and representing Singapore's major ethnic groups--Chinese, Indians and Malays--were studied. GADab and IA-2ab frequencies, and association of autoimmunity status with clinical and biochemical profiles were analysed.
RESULTS: Radio-immunoprecipitation assays detected either or both antibodies (seropositivity) in 41.9% of subjects with type 1 diabetes. GADab was detected in 36.6% and IA-2ab in 23.7% of type 1 diabetics. Prevalence of IA-2ab showed a reduction in frequency with disease duration (P = 0.026). In clinical type 2 diabetics, seropositivity was 10.0% with higher frequency in Malays (17.5%) than Chinese (9.7%) and Indians (4.5%). Multivariate analysis revealed that low fasting C-peptide was associated with seropositivity (odds ratio (OR) = 0.15; 95% confidence interval (CI) = 0.04-0.58). A significant relationship (OR = 13.5; 95% CI = 5.0-36.7) between insulin requirement and duration (>5 years) was also revealed. In patients with type 2 diabetes there was a trend of gradual progression to insulin dependency. However, there was considerable variation in body mass index between ethnic subgroups of type 2 diabetics, particularly for Chinese (mean (SD) = 26.0 (4.7)) and Malays (mean (SD) = 29.2 (5.9); P < 0.001).
CONCLUSIONS: Presence of both antibodies in our mixed ethnic group of type 1 diabetes patients was much lower than in Caucasians. Significant numbers of patients were seronegative for antibodies. Influences due to ethnicity and adiposity would require further investigations.
A country-wide diabetic survey of the population (age 15 years and above) of Singapore shows that the prevalence of diabetes mellitus in Singapore is 1.99 percent. It is commoner in males (2.36 percent) than in females (1.64 percent). The prevalence of diabetes in the age group 15-39 years is only 0.40 percent and in the age group 40 years and older it is 5.08 percent. The prevalence of diabetes in Indians (6.07 percent) is significantly higher than that in Malays (2.43 percent) and Chinese (1.55 percent). Indian diabetics have an insignifi"cantly higher incidence of positive family of diabetes (12.7 percent) than Malays (10.9 percent) and Chinese (6.5 percent). Obesity was commoner in Malay diabetics (67.4 percent) than in Chinese diabetics (41.6 percent) and Indian diabetics (35.7 percent). The survey shows that 40.4 percent of the diabetics are known while 59.6 percent of the diabetics are newly diagnosed. The majority of the diabetics are treated with oral hypoglycaemic drugs (71.5 percent) and only 4.8 percent are receiving insulin injections. A mong the female diabetics, 63.0 percent have 4 or more pregnancies and large babies at birth are recorded in 12.3 percent. In the newly diagnosed diabetics, 64.3 percent have no symptoms. The complications of the diabetics are hypertension (26.8 percent), nephropathy (9.8 percent), retinopathy (8.5 percent), coronary heart disease (6.1 percent), skin infection (4.6 percent) and neuropathy (3.3 percent). The high prevalence of diabetes among the Indians is likely to be due to a genetic predisposition coupled with an environmental factor (obesity), although this hypothesis is not conclusively demonstrated by the present study.
Singapore is a tropical island city-state with a population of 2.4178 million consisting of Chinese (76.7%), Malays (14.7%), Indians (6.4%) and other races (2.2%). A diabetic survey of the adult population, aged 15 years and above, carried out in 1975, shows that the prevalence of diabetes is 1.99%; it is higher in males (2.36%) than in females (1.64%). It occurs mainly in the age group 40 years and above (5.08%) and is uncommon in the age group 15-39 years (0.40%). In males, the highest prevalence of diabetes (7.0%) is in the age group 45-49 years while in females the highest prevalence (7.2%) is in the age group 55-59 years. 43.3% of the diabetics are of normal weight while 44.3% are overweight and 12.4% are underweight. 59.6% of the diabetics are newly diagnosed while 40.4% are known diabetics; 64.3% of the newly diagnosed diabetics have no symptoms. The prevalence of diabetes among the Indians (6.07%) is significantly higher than that in Malays (2.43%) and Chinese (1.55%). Indian diabetics have a slightly higher positive family history of diabetes (12.7%) than Malays (10.9%) and Chinese (6.5%). Obesity is commoner in Malay diabetics (64.7%) than in Chinese (41.6%) and Indians (35.7%). The possible factors leading to the significantly higher prevalence of diabetes among the Indians compared to the other ethnic groups in Singapore are discussed. It is suggested that the Indian gene is susceptible to diabetes (diabetic genotype) and increased food consumption, altered lifestyle and greater obesity leads to the expression of diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)