Can better hygiene generate an increase of type 1 diabetes frequency?

Abstract

Variety of epidemiological studies indicate a steady increase in the incidence of type 1 diabetes mellitus, especially in industrialized countries, contrasted by a gradual decrease in the incidence of infectious diseases. There is an overall North–South gradient for type 1 diabetes and other immune disorders in North America and Europe, and West–East gradient in Europe. In developed countries lowest type 1 diabetes frequency is reported in the areas with the poorest socio-economic and hygiene conditions. There are several hypotheses that attempt to explain the relationship between lower exposure to transmissible agents, and a higher incidence of cases of allergic or autoimmune diseases (including type 1 diabetes mellitus). These are: the concept of the antigen competition, the phenomenon of bystander suppresion or “polio” hypothesis. According to hygiene hypothesis increased hygiene may contribute to imbalance of the autoimmune system, facilitating autoimmune reactions leading to destruction of islet beta cells and lack of endogenous insulin.