Perinatal risk factors for atopic disease in conscripts

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Abstract
Background There is evidence to suggest that atopic disease in adulthood could be manifestations of events in early life. Objectives To investigate the relationship between perinatal risk factors and the prevalence of allergic rhinitis and asthma in conscripts. Methods A retrospective cohort study, where information from the Military Service Enrolment Register was linked to the national Medical Birth Register. The study included 149 398 male conscripts who were born in Sweden in 1973, 1974 and 1975. Outcome measures were current asthma and allergic rhinitis recognized at the compulsory military conscript examinations. Results Unifactorial analyses demonstrated that number of older siblings, young maternal age, multiple gestation, prematurity, low birth weight, growth retardation and perinatal asphyxia were all significantly related to a decreased risk of allergic rhinitis among male conscripts. The prevalence rates of allergic rhinitis among conscripts with and without older siblings were 14.1% and 16.2%, respectively (odds ratio 0.85; 95% confidence interval 0.82–0.87). The prevalence rates of allergic rhinitis among those with term birth (>36 weeks), moderately preterm birth (33–36 weeks) and very preterm birth (<33 weeks) were 15.2%, 13.1% and 11.6%, respectively. Older siblings, multiple gestation and young maternal age were highly significant independent determinants of allergic rhinitis. By contrast, the effects of prematurity, low birthweight and asphyxia were weaker and highly correlated. The only independent determinants of asthma were maternal age, birthweight and multiple gestation. Furthermore, maternal age and birthweight had opposite effects on asthma and allergic rhinitis. Conclusions In contrast to asthma, allergic rhinitis in young adult men was strongly associated with perinatal events. This may reflect the close relationship between allergic rhinitis and atopic sensitization, whereas asthma has a more multifactorial aetiology.