Participants were sourced from the Tasmanian Longitudinal
Health Study (TAHS) (previously known as the Tasmanian Asthma
Study), which began in 1968 with the recruitment of 8583 children
then aged 7 and enrolled in Tasmanian primary schools. The aim of
the original study was to examine determinants of childhood
respiratory health. Since the original survey in 1968, there have
been several follow-up studies on this cohort to investigate the
lifetime risk factors for chronic respiratory diseases in middle-age,
including the role of childhood respiratory diseases. The most recent
TAHS follow-up was completed in 2004–2005, when 88% (n=7,562)
of the original 1968 cohort was traced (Wharton et al., 2006) with a
response rate of 78% (n=5,729) to a postal survey.