Infections in early childhood and risk of atopic disease

Having more siblings has been shown to be associated with lower risk of ato pic diseases. This might be due to the higher number of infections in large r families. Because children attending day care centres have more respirato ry infections, we analysed the association of number of siblings and day ca re attendance in children aged 1-3 y with atopic disease in a cross section al survey of 8387 schoolchildren aged 13-14 y and their parents in four reg ions of Finland. Having no siblings, compared to three or more siblings, wa s associated with significantly higher risk of Lifetime history of hay feve r (odds ratios (OR) 1.53, 95% confidence interval (CI) 1.25-1.86) and atopi c eczema (OR 1.28, 95%CI 1.04-1.56), and higher risk (ns) of doctor-diagnos ed asthma ever (OR 1.26, 95%CI 0.85-1.88), Less strong associations were ob served with the number of older siblings (birth order). No associations wer e observed with current symptoms of these diseases during the last 12 mo. A ttending a day care centre at the age of 1-3 y was not associated with decr eased risk of any of the atopic diseases studied, but, in contrast to the h ypothesis, 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 o ther factors than early childhood respiratory infections explain the associ ation between number of siblings and future risk of atopic disease.