Cumulative incidence of asthma diagnosis at the age of seven in a birth cohort

Objectives: The aim of this study was to follow a cohort of children in a defined region from birth up to the age of seven for the occurrence of a doctor's diagnosis of asthma in the medical records in primary healthcare and hospital.Methods: In a defined region in Sweden with a population of about 150,000 inhabitants, all children (n=2104) born in the University Hospital in 1990 were recorded. Seven years later, 82% (n=1752) were still living in the region; their medical files at the Department of Paediatrics and all primary healthcare centres in the region were checked for an asthma diagnosis (ICD 9).Results: The results gave a total cumulative asthma incidence of 10.9% among seven-year-old children in the studied region. A significantly (p<0.01) higher number of boys (13.1%) than girls (8.5%) had this diagnosis. The incidence of asthma was highest (p<0.005) among boys living in urban areas at the age of seven. Increased relative risks for asthma were also found among children born in the autumn (p<0.05...