Aetiology. Non-insulin-dependent diabetes.

NIDDM appears to be a disease of complex aetiology. Although specific genetic markers for the disease have yet to be defined, there is clear evidence for genetic predisposition, with high concordance in monozygous twins. However, concordance is incomplete, and there are therefore additional, non-genetic, mechanisms which are responsible for increasing the risk of the disease in susceptible subjects. At the present time, the most plausible environmental precipitants appear to be the inter-related triad of obesity, low levels of habitual physical exercise and diet. The power of environmental determinants, and their interaction one with another, may also be subject to individual genetic determination, and may not act in a similar manner in all populations. Some non-Caucasian populations, which have undergone marked sociocultural change, are now extremely susceptible to NIDDM. This is probably the result of evolutionarily heightened genetic predisposition, compounded by strong environmental influence resulting from the recent changes in their human ecology. Since prevalence is strongly related to age, NIDDM also represents a growing problem to the world's industrialized societies, for many of which longevity is now the major demographic trend. Research into the aetiology of NIDDM must not only continue, it must also explore new directions, and attain greater scientific depth and sophistication, if it is to make a useful contribution to the eventual prevention and control of the disease.