CHEST ILLNESS IN INFANCY AND CHRONIC RESPIRATORY-DISEASE IN LATER LIFE - AN ANALYSIS BY MONTH OF BIRTH

Background. Cohorts born at different times of year differ in their risk of exposure to seasonal respiratory infections in early life, but are likely to have similar socioeconomic status and lifestyle thereafter. Methods. We investigated the long-term consequences of acute chest illness in infancy for later development of chronic respiratory disease by analysing variations by month of birth in hospital admissions for respiratory illness (total n = 49 866), chronic respiratory symptoms and ventilatory function among British school children (n = 11 482) and middle-aged adults (total n = 55 829). Results. Admission for bronchiolitis in the first year of life was three times more common for infants born September to November (autumn) than those born March to May, yet people born in the autumn experienced fewer respiratory symptoms and had better ventilatory function. In two surveys of middle-aged men, forced expiratory volume in one second/forced ventilatory capacity (FEV(1)/FVC) was significantly (P = 0.025) higher among autumn births. Hospital admissions for chronic bronchitis/emphysema and pneumonia varied little with season of birth. Admissions for asthma were significantly (P < 0.05) more common among children and young adults born in the autumn. Conclusions. These findings do not support the hypothesis of a causal link between chest illness in infancy and the later development of chronic bronchitis and emphysema. The variation in asthma admissions with month of birth deserves further investigation.