The effect of selected risk factors, including the mode of delivery, on the development of allergic rhinitis and bronchial asthma

Introduction: Cesarean section affects the process of colonization by bacteria transferred from the mother's skin and hospital bacteria, which in turn contributes to development of allergic conditions. Aim: To assess selected risk factors, including the mode of delivery, parity, and the role of genetic factors for the development of allergic rhinitis and bronchial asthma. Material and methods: The study was conducted in 18,617 respondents aged 6-7, 13-14, and 20-44 years who completed the ECRHS II and ISSAC questionnaires. Thirty percent of the study population underwent complementary assessments in the form of skin-prick tests, serum IgE levels, lung function tests, and peak nasal inspiratory flow (PNIF). The study is a part of the Epidemiology of Allergic Disorders in Poland (ECAP) study conducted in 8 areas in Poland (Warsaw, Lublin, Bialystok, Gdansk, Poznan, Wroclaw, Katowice, Krakow, and two rural areas - Zamosc and Krasnystaw counties). Results: Respondents diagnosed with allergic rhinitis were at a significantly higher risk of inheriting the allergic condition if their mother (OR = 2.17; 95% CI: 1.98-2.39, p = 2.00 x 10(-16)) or father (OR = 2.20; 95% CI: 1.96-2.47; p = 2.00 x 10(-16)) suffers from this allergy. Conversely, in the group diagnosed with bronchial asthma, the highest risk of an inherited allergy was observed in situations where maternal (OR = 2.00; 95% CI: 1.57-2.55; p = 1.69 x 10(-5)) or paternal (OR = 1.94; 95% CI: 1.42-2.66; p = 3.61 x 10(-5)) grandparent was affected. Moreover, the risk of developing allergic rhinitis depended on the mode of delivery: i.e. it was higher for a Cesarean section (OR = 1.20; 95% CI: 1.01-1.43; p = 0.04) than vaginal delivery (OR = 0.88; 95% CI: 0.78-0.99; p = 0.03). The higher the number of siblings, the lower the risk of allergic rhinitis. Conclusions: Allergy risk factors, especially those predisposing to allergic rhinitis, include not only genetic factors but also the mode of delivery: vaginal delivery or Cesarean section.