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Infections in early childhood and risk of atopic disease
J Pekkanen1, S Remes, M Kajosaari
1Unit of Environmental Epidemiology, National Public Health Institute, Kuopio, Finland. Juha.Pekkanen@ktl.fi
Insights
Having fewer siblings increases the risk of developing atopic diseases like hay fever and eczema. Early childhood daycare attendance did not reduce this risk and may slightly increase hay fever symptoms.
Area of Science:
- Epidemiology
- Allergology
- Pediatrics
Background:
- A larger number of siblings is linked to a reduced risk of atopic diseases.
- This protective effect is hypothesized to be due to increased infection exposure in larger families.
- Children in daycare centers experience more respiratory infections, prompting investigation into this factor.
Purpose of the Study:
- To analyze the association between the number of siblings and daycare attendance in early childhood (ages 1-3) with atopic disease risk.
- To examine the relationship between sibling number and lifetime history or current symptoms of atopic diseases in adolescents.
- To investigate if early childhood respiratory infections mediate the sibling-atopy association.
Main Methods:
- Cross-sectional survey of 8387 schoolchildren aged 13-14 years and their parents in Finland.
- Data collected on the number of siblings, daycare attendance (ages 1-3), and history of atopic diseases (hay fever, eczema, asthma).
- Statistical analysis using odds ratios (OR) and 95% confidence intervals (CI) to assess associations.
Main Results:
- Having no siblings was significantly associated with a higher risk of lifetime hay fever (OR 1.53) and atopic eczema (OR 1.28).
- A trend towards increased risk of doctor-diagnosed asthma was observed for children with no siblings (OR 1.26).
- Daycare attendance was not associated with reduced atopic disease risk; instead, it showed a slight increase in current hay fever symptoms (OR 1.34).
Conclusions:
- The findings suggest that factors other than early childhood respiratory infections explain the link between sibling number and atopic disease risk.
- The protective effect of having more siblings against atopic diseases may not be solely mediated by infection exposure.
- Further research is needed to elucidate the complex interplay of genetic and environmental factors influencing atopic disease development.
Abstract:
Having more siblings has been shown to be associated with lower risk of atopic diseases. This might be due to the higher number of infections in larger families. Because children attending day care centres have more respiratory infections, we analysed the association of number of siblings and day care attendance in children aged 1-3 y with atopic disease in a cross sectional survey of 8387 schoolchildren aged 13-14 y and their parents in four regions of Finland. Having no siblings, compared to three or more siblings, was associated with significantly higher risk of lifetime history of hay fever (odds ratios (OR) 1.53, 95% confidence interval (CI) 1.25-1.86) and atopic eczema (OR 1.28, 95%CI 1.04-1.56), and higher risk (ns) of doctor-diagnosed asthma ever (OR 1.26, 95%CI 0.85-1.88). Less strong associations were observed with the number of older siblings (birth order). No associations were observed with current symptoms of these diseases during the last 12 mo. Attending a day care centre at the age of 1-3 y was not associated with decreased risk of any of the atopic diseases studied, but, in contrast to the hypothesis, was associated with slightly increased risk of current symptoms of hay fever (OR 1.34, 95%CI 1.12-1.60). The present results suggest that other factors than early childhood respiratory infections explain the association between number of siblings and future risk of atopic disease.