Genetic and environmental influence in the epidemiology of noninsulin-dependent diabetes mellitus: A global perspective

Refinement of the classification of diabetes mellitus to include two major categories, insulin dependent (IDDM) and noninsulin-dependent (NIDDM) and the recent attention paid to the standardization of epidemiological techniques have led to much new information on the epidemiology of the disease. Support for the notion of genetic influence in the development of NIDDM has come from twin studies, but the search for specific genetic markers for NIDDM has been largely unproductive to date. There is increasing scepticism as to the utility of the chlorpropamide-alcohol flush as genetic marker for NIDDM. The large disparity in the frequency of NIDDM between populations provides indirect support for the genetic hypothesis, as do recent studies of the association between NIDDM and ancestral genetic admixture. Obesity has long been considered a causal factor in the aetiology of NIDDM, though the strength and consistency of this relationship is now being questioned. The strength of the association between obesity and NIDDM has been shown to vary depending on the presence or absence of a family history of the disease. There is further preliminary evidence to suggest that association between obesity and NIDDM may vary in strength between populations, and between the sexes. Little evidence has so far emerged for a role of quantitative or qualitative aspects of diet in the aetiology of NIDDM. This may be due, in part, to the imprecision of current techniques for dietary estimation. The role of physical inactivity in the genesis of NIDDM is gaining increasing support from some diabetologists, but, once again, studies are hindered by the lack of objective and reliable measurement procedures. Other 'environmental' factors which may be associated with NIDDM include socio-economic status, parity and psychosocial stress. Analytic epidemiology is playing a growing role in the elucidation of the genetic and environmental determinants of NIDDM. As the science of public health, epidemiology may provide a framework for the eventual prevention of this common and debilitating disease.