Early wheezing phenotypes and cognitive development of 3-yr-olds. Community-recruited birth cohort study.

The main purpose of the study was to answer the question whether young children without clinical diagnosis of asthma but experiencing early wheezing disorders and therefore being at high risk of developing asthma may have cognitive deficits. In the ongoing birth cohort study wheezing symptoms were recorded postpartum over two first years of age and subsequently cognitive status of children at the age of 3 yr was assessed with the Bayley Mental Development Index (MDI). In the statistical analysis a wide range of modifying and confounding factors (maternal education, gender of children, prenatal exposure to lead and environmental tobacco smoke (ETS) were considered to assess the independent effect of early wheezing phenotypes on cognitive development of children. The MDI score correlated inversely with the number of wheezing days recorded over 24 months (r = -0.13, p = 0.007), lead cord blood concentration (r = -0.12, p = -0.02), number of siblings (r = -0.17, p = 0.0006) and the number of cigarettes smoked daily by other household members at home over the pregnancy period (r = -0.18, p = 0.0002). While the children who experienced wheezing over the first year of age showed deficit of 2 MDI scores (beta coeff. = -2.31, 95%CI: -4.63 to 0.02), those with persistent wheezing had the score deficit of 4 points (beta coeff. = -4.41, 95%CI: -8.27 to -0.55). To our knowledge, it is the first report in the iterature showing that early wheezing is associated the cognitive deficit in a community-recruited very young children. Observed cognitive deficit in early wheezers may be caused by RSV infections or can be related to lower lung function attributed to persistent wheezing, which reducing oxygen supply would affect rapidly developing brain.