| Summary: | The worldwide prevalence of type 2 diabetes (T2D) has increased dramatically over the past half-century and is continuing to rise at a rapid rate, along with increasing levels of obesity. These changes are having a profound effect on healthcare planning and provision in many countries. Strong environmental effects in T2D risk are clear from longitudinal studies. In addition, groups with traditional lifestyles who migrate to a more ‘Westernised’ environment and lifestyle suffer increased diabetes prevalence. Environmental factors, however, do not seem to explain all of the variance in type 2 diabetes prevalence, nor all the variance in response to intervention studies. Offspring of patients with type 2 diabetes have about a three-fold higher risk of developing the disease than those with no diabetes family history. Diabetes prevalence also differs between ethnic groups within countries. South Asian populations living in the UK and US have approximately 4-6 times the risk of developing diabetes compared to those of European descent. This effect may also be evident in other Native American populations such as the Mapuche in Chile. Mapuche populations living a traditional rural lifestyle appear to be relatively protected, on limited data, against diabetes risk (prevalence of ~1% to ~4%; but this risk increases markedly in the urban environment (6.2 to 8.2%). These observations suggest that genetic predisposition is also a factor in determining diabetes risk, but this is complicated by gene-environment interactions, where individuals with different genotypes respond differently in different environments.
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