The survey measures asthma levels among children

Most research on the growth of the condition dates back to the 1980s - but Aberdeen University led the way in 1964 when it surveyed primary school pupils.

The exercise was repeated in 1989 and is now carried out every five years.

The number of children with asthma has almost trebled since 1964. The latest questionnaire is issued next week.

It will target schools which fall within the 1960s city boundaries and mainly features the same questions asked four decades ago.

Research fellow Dr Geraldine McNeill said the study has identified a large increase in asthma levels between 1964 and 1989.

Asthma-like symptoms

"That is beginning to level off, but we would like to know whether that levelling-off has continued or whether it is going up again," she said.

In 1964, asthma-like symptoms were reported by an average of four pupils in a class of 40.

That had risen to 11 by the time of the survey in 1999.

The last survey found a quarter of children had experienced wheezing

Forty years ago boys with asthma outnumbered girls by two to one, but the latest figures suggested that the two sexes were almost equal.

Shona Haslam, from Asthma UK Scotland, said: "It's got huge implications for NHS planning over the next 20 to 30 years.

"If we have the highest rate of teenage asthma now, then we are going to have the highest rate of adult asthma in 20 years time."