Handbook of Diabetes, 4th Edition, Excerpt #5: Epidemiology and aetiology of type 1 diabetes
The geographical variation within Europe has been highlighted by the EURODIAB epidemiology study…a north-south gradient…Prevalence is predicted to rise from 94,000 (2005) to 160,000 in 2020 in Europe. This suggests that environmental influences may predominate over genetic susceptibility in causing or triggering the disease.…One model of the evolution of type 1 diabetes is that individuals destined to develop the disease are born with genes that confer predisposition and they outweigh any genes with protective effects (Figure 6.15). Environmental factors then act as triggers of the T cell-mediated autoimmune destructive process, which results in insulitis, β cell injury and loss of β cell mass. As β cell function declines, there is loss of the first-phase insulin response to intravenous glucose, subsequent glucose intolerance (pre-diabetes) and eventually the clinical onset of overt diabetes. An alternative view is that there is a chronic interaction between genetic susceptibility, cumulative exposure to environmental factors and immune regulatory processes over the entire period until a critical loss of β cell mass results in insulin deficiency and hyperglycemia…These events are assumed to proceed more rapidly in children.