COHORT PROFILE Cohort Profile: The Leicester Respiratory Cohorts

Asthma and other wheezing disorders are the most common chronic health problems in childhood and place a large burden on children, their families and society. Prevalence is highest in infancy or early childhood and the aetiology is complex, with a strong influence of intrauterine and early life exposures. Clinical presentation, response to treatment and prognosis differ by age and the natural history is highly variable. It has been questioned whether asthma, especially in young children, should be regarded as one disease with a single underlying aetiology but a wide range of severity, or as a syndrome comprising several separate conditions. Furthermore, respiratory illness in early life is associated with adult respiratory disease and diminished lung function. Despite this, most epidemiological studies of asthma before the 1990s had focused on schoolchildren and adults, and there were sparse population-based data on infants and preschool children. The Leicester respiratory cohort studies were set up to fill this gap. The first Leicester cohort was established in 1990 by Hamish Simpson (with David Luyt and Adrian Brooke as principal fellows) as a community-based sample of 1650 children born between 1985 and 1990. This study provided the first data on prevalence and subsequently on natural history of preschool wheeze in Europe. The large agespread of the Leicester 1990 cohort permitted an overview of the prevalence and characteristics of wheeze in preschool children, but complicated studying the natural history. This cohort was relatively small and did not include ethnic minority groups. Therefore, Michael Silverman and Claudia Kuehni recruited a second cohort in 1998, consisting of 8700 children born between 1993 and 1997. A stratified sampling design was used to recruit 5400 children aged 1, and 3300 children aged 2–4 years. Of these, 6100 were white and 2600 were south Asians.