Genetic and epidemiological aspects of diabetes mellitus

Abstract

Using an interview-questionnaire technique, the frequency of insulin-taking diabetics in the families of non-insulin-taking diabetics, and vice-versa, is compared with the frequencies in control families and in the general population. The results suggest that these two forms of diabetes are not genetically distinct. Early-onset, insulin-dependent diabetics show indications of dominant inheritance in their families more often than do diabetics of other types. Cardiovascular complications, at least in late-onset, insulin-taking diabetics, are found to occur more rapidly, and to be more severe, in individuals with a strong family history. Diabetics and controls are examined for a range of red and white cell polymorphisms, serum proteins and isoenzymes. In some of these systems, the control group exhibits significant heterogeneity with regard to age. Comparison of the diabetic population with matched controls shows no significant associations except in the case of the ABO system, where older diabetics, especially males, show a higher frequency of group A(_1) and in the HLA system, where insulin-taking diabetics show higher frequencies of the B8 and Bwl5 alleles. It is suggested that the apparent association with ABO is the result of differential mortality amongst non-diabetics rather than any increased liability to the disease of group A(_1)individuals. Associations with the HLA system show a relationship with age at diagnosis which may explain certain inconsistencies in previously published reports. The prevalence of clinically diagnosed diabetes in the Durham area in 1975 exceeds that reported previously for other British populations. The presentation of new cases of insulin-requiring diabetics has a marked peak in February.