Early social mixing and childhood Type 1 diabetes mellitus: a case-control study in Yorkshire, UK

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Abstract
Aims Evidence from animal models shows an increased risk of Type 1 diabetes mellitus associated with the absence of early life exposure to pathogens. To test this ‘hygiene hypothesis’, patterns of social mixing and infections in the first year of life and the risk of developing autoimmune diabetes in childhood were examined. Methods Personal interviews were conducted with the mothers of 220 children with Type 1 diabetes (0–15 years) and 433 age/sex matched controls from a population-based case control study in Yorkshire, UK. Social mixing including attendance at daycare, and infections occurring under 1 year of age were measures of exposure. Adjusted odds ratios (OR) were derived using conditional logistic regression. Results Frequency of attendance at daycare during the 1st year of life was inversely associated with childhood diabetes (OR 0.71, 95% confidence interval 0.51–1.00, P = 0.05), a finding not explained by mother's age, level of education or maternal diabetes. Increasing numbers of children in the daycare setting and numbers of sessions attended were significantly associated with increasing protection from diabetes. The strongest effect was observed in children with diabetes diagnosed aged 0–4 years. Conclusions Social mixing through attendance at daycare in early infancy appears to confer protection against the development of childhood diabetes. This may be mediated through exposure to infectious agent(s) as a significant dose–response effect was evident with increasing numbers of child ‘contacts’. These findings suggest early infectious exposure may play a role in the development of immunoregulatory mechanisms which protect against diabetes and further work is warranted.