Changes in the prevalence of asthma, eczema and hay fever in pre-pubertal children: a 40-year perspective.

Surveys of primary schools children in Aberdeen carried out in 1964, 1989, 1994 and 1999 suggested a slowing of the increase in parent-reported wheeze between 1994 and 1999. To assess whether this pattern had continued, questionnaires were distributed to 5712 children aged 7-12 years in the same schools in 2004. A total of 3271 (57.3%) completed questionnaires were returned. As in earlier surveys the results were divided into those for younger children (school years 3-4; age 7-9 years) and older children (school years 5-7; age 9-12 years). Compared with 1999, the 2004 results showed a decrease in the proportion of children with wheeze in the last 3 years from 30.1% to 23.3% (P < 0.001) in the younger group and from 27.6% to 25.1% (P = 0.052) in the older group. There was no significant change in the lifetime prevalence of asthma in either the younger or the older group, but the lifetime prevalence of eczema and hay fever increased by around 10% in both the younger and older groups (all P < 0.001). The differences in the time trends for the different conditions suggest that the causal factors for wheeze and asthma differ from those for other allergic diseases of childhood.