Seedat Ma

South African Indians Show a High Prevalence of NIDDM and Bimodality in Plasma Glucose Distribution Patterns

OBJECTIVE To determine the prevalence of diabetes mellitus and impaired glucose tolerance (IGT) and to test for bimodality in the plasma glucose distribution in South African Indians. RESEARCH DESIGN AND METHODS Subjects were selected by systematic cluster sampling in various areas of Durban. They underwent a modified glucose tolerance test whereby fasting and 2-h postglucose (75 g) plasma glucose levels were measured. The program MIX was used to test for bimodality in the plasma glucose distribution. RESULTS We tested 2,479 subjects (1,441 women and 1,038 men). Based on the revised World Health Organization criteria, the crude prevalence of diabetes mellitus was 9.8%, and the crude prevalence of IGT was 5.8%; the age- and sex-adjusted prevalence was 13.0 and 6.9%, respectively. IGT was significantly more common in men (7.6%) than in women (4.4%). Obesity was a feature of both diabetes mellitus and IGT, particularly in women. Both fasting and 2-h plasma glucose values did not conform to a single normal distribution pattern in any age-group, whereas unequivocal evidence of bimodality was seen in the 55- to 74-year age-group of both sexes for fasting and 2-h glucose and also in the 2-h levels of men in the 25- to 34-year age-group. CONCLUSIONS This study has highlighted a high prevalence of non-insulindependent diabetes mellitus in South African Indians and bimodality in the plasma glucose distribution.

The significance of a positive family history in South African Indians with non-insulin-dependent diabetes (NIDDM)

A group of South African Indians with NIDDM participated in a study to evaluate the frequency of positive family histories of the disease and to determine the relative contribution of maternal or paternal genetic determinants. Information was elicited by means of an interview and recorded. Of the 1098 diabetic subjects studied 70% gave a positive family history of a first degree relative suffering from NIDDM. Three-generation transmission was recorded in 5.3% of the subjects. A significantly greater proportion of probands (40%) had a mother with NIDDM than those with a father (26%). A positive family history in an offspring was more common in female probands (10.6%) than males (5.5%). Twice as many probands with 3 generation transmission had a maternal grandmother suffering from NIDDM (2.5%) compared with those who had a paternal grandmother afflicted (1.2%) (P < 0.05), whereas the frequencies in the maternal (0.9%) and paternal (0.8%) grandfathers were similar. This study has highlighted, not only the high prevalence of a positive family history in South African Indians with NIDDM, but also a stronger maternal contribution to the putative gene responsible for the disease.

HLA Class I and II Antigens in South African Indians With NIDDM

The relationship between the HLA system and non-insulin-dependent diabetes mellitus (NIDDM) in South African Indians, a migrant Indian group, was evaluated by testing HLA-A, -B, and -C antigens in 184 patients and 1444 control subjects and HLA-DR antigens in 104 patients and 330 control subjects. There was a significant increase in the frequency of HLA-Bw61 in patients compared with control subjects (27.7 vs. 18%, P = .00155), although the degree of association was not very strong (relative risk 1.7). A similar association has been noted in Fiji Indians, another migrant Indian group. However, no relationship could be established at the DR locus. It is suggested that the relatively high frequency of the Bw61 allele in South African Indians could, in the presence of some environmental factor like obesity, confer increased susceptibility to NIDDM.