Abstract
Background. The hygiene hypothesis attributes the increased incidence of type 1 diabetes (T1D) to a decrease of immune system stimuli from infections. We evaluated this prospectively in the Diabetes Autoimmunity Study in the Young (DAISY) by examining daycare attendance during the first two years of life (as a proxy for infections) and the risk of T1D. Methods. DAISY is a prospective cohort of children at increased T1D risk. Analyses were limited to 1783 children with complete daycare and breastfeeding data from birth to 2 years of age; 58 children developed T1D. Daycare was defined as supervised time with at least one other child at least 3 times a week. Breastfeeding duration was evaluated as a modifier of the effect of daycare. Cox proportional hazards regression was used for analyses. Results. Attending daycare before the age of 2 years was not associated with T1D risk (HR: 0.89; CI: 0.54–1.47) after adjusting for HLA, first degree relative with T1D, ethnicity, and breastfeeding duration. Breastfeeding duration modified this association, where daycare attendance was associated with increased T1D risk in nonbreastfed children and a decreasing T1D risk with increasing breastfeeding duration (interaction P value = 0.02). Conclusions. These preliminary data suggest breastfeeding may modify the effect of daycare on T1D risk.
Highlights
The hygiene hypothesis attributes the increased incidence of type 1 diabetes (T1D) to a decrease of immune system stimuli from infections
Our analyses showed that breastfeeding duration interacted with daycare attendance, where daycare attendance was associated with increased risk of T1D in nonbreastfed children and a decreasing risk of T1D with increasing breastfeeding duration (Table 2)
We found that breastfeeding modified the effect of daycare, where daycare attendance was associated with increased risk of T1D in nonbreastfed children and a decreasing risk of T1D with increasing breastfeeding duration
Summary
The hygiene hypothesis attributes the increased incidence of type 1 diabetes (T1D) to a decrease of immune system stimuli from infections. We evaluated this prospectively in the Diabetes Autoimmunity Study in the Young (DAISY) by examining daycare attendance during the first two years of life (as a proxy for infections) and the risk of T1D. Attending daycare before the age of 2 years was not associated with T1D risk (HR: 0.89; CI: 0.54–1.47) after adjusting for HLA, first degree relative with T1D, ethnicity, and breastfeeding duration. Parslow et al observed a significant association with higher incidence of T1D for children 0–14 years of age in areas with low levels of social mixing [7]. In Austria, Schober et al examined social mixing through population density and observed protection from T1D in areas with high percentages of children less than 15 years of age [5]
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