From a studies carried out on 12 year olds in a region of Wales in 1973 and 1988.

The prevalence of a history of wheeze at any time had increased from
17% to 22%, while that of a history of asthma at any time had increased from 6% to 12%.
Current asthma had increased from 4% to 9%, but wheezing in the past year not attributed to
asthma had remained at 6%. The exercise provocation tests suggested that both mild and severe
asthma had become more common. Increases had also occurred in the frequencies of a history of
eczema (from 5% to 16%) and of hay fever (from 9% to 15%).