Early life risk factors for asthma from childhood until age 28 years

Background: There is a lack of longitudinal studies about asthma where cohorts have been followed from childhood up to adult age. Aim: to evaluate risk factors in early childhood in relation to asthma onset at different ages. Method: The first pediatric cohort within the Obstructive Lung Disease in Northern Sweden (OLIN) was recruited in 1996. Parents of 8 year old children completed a questionnaire about asthma, allergic diseases and risk factors and n=3430 (97%) participated and 2148 performed skin prick test. The cohort was followed with annual questionnaires from 8 to 19y and by postal questionnaire at 28y (67% of the original cohort). Age at onset: pre-school (<8y), pre-teenage (8 to 13y), teenage (13 to 19y), or young adulthood (19 to 28y). Risk factors were analyzed by multinomial regression analyses. Results: Throughout the cohort study, 675/3430 (19.7%) reported asthma in any of the surveys, females 20.2% and males 19.2%. Female sex was a protective factor against pre-school onset asthma (OR 0.6) and a risk factor for teenage onset asthma (OR 1.7). Family history of asthma (ORs 1.6-3.3) and allergic sensitization at 8 years (ORs 2.1-3.1) was consistently significantly associated with asthma-onset at all ages. Low birthweight and breastfeeding <3months were of importance for asthma onset in childhood and in young adulthood, while maternal smoking during pregnancy, severe respiratory infection, rhinoconjunctivitis and eczema were associated with pre-school and pre-teenage asthma onset. Conclusion: In this prospective cohort study with long-term follow-up, risk factors occurring both before and after birth were associated with asthma onset throughout childhood until young adulthood.