Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial

Background Asthma places huge demands on healthcare services, and its preva lence is increasing. Reduction of exposure to environmental allergens could offer a realistic chance for primary prevention. Our aim was to ascertain whether or not living in a low-allergen environment reduces the risk of ast hma and atopic diseases in infants. Methods We assigned infants to four risk groups according to parental atopi c status. We enrolled 291 high-risk couples (both parents atopic, no pets) into a prospective, prenatally randomised, cohort study, and allocated them to environmental manipulation, in which measures to reduce prenatal and po stnatal allergen exposure were undertaken (active HRA) (n=145) or no interv ention (control HRC) (n=146). Two further prospective groups were studied: 161 high-risk infants with pets in the home (HRP group) and 168 low-risk in fants, whose parents were both non-atopic (LR group). The main outcome meas ures were signs and symptoms of atopic disease at 1 year of age. Findings 103 families dropped out or were lost to follow up. At age 1 year we followed-up 133 HRA, 118 HRC, 140 HRP, and 126 LR infants. Children in t he HRA group were less likely to have respiratory symptoms during the first year of life than those in the HRC group. The most pronounced differences were in the relative risks for severe wheeze with shortness of breath (rela tive risk 0.44 [95% CI 0.20-1.00]), prescribed medication for the treatment of wheezy attacks (0.58 [0.36-0.95]), and wheezing after vigorous playing, crying, or exertion (0.18 [0.04-0.79]). Probability of respiratory symptom s in HRC and HRP infants was similar, whereas it was much lower in the LR t han in the HRC group. Cat ownership was significantly associated with sensi tisation to cats (24.6 [3.04-199.05]; p=0.003). Interpretation Environmental manipulation reduces some respiratory symptoms in the first year of life in high-risk infants. Further follow up is neede d, however, to ascertain whether living in a low-allergen environment reduc es allergy and asthma in later life.