Researchers studying a school-based programme credited with reducing the rates of obese and overweight 7-year-olds have now found a reduction in asthma symptoms.
Asthma is a potentially serious breathing disorder in which airways become inflamed. Its causes are not known, but in many cases it is linked to allergies.
Project Energize, a healthy-nutrition and physical activity scheme, began as a trial in Waikato in 2004 and was later converted to an intervention funded at all Waikato primary schools by the area's district health board.
In five years, the proportion of 7-year-olds who were overweight - the group in which the greatest change in body mass index occurred - declined by 4 percentage points. There was a smaller fall in the obesity rate for 7-year-olds and the picture was more mixed for older children.
Now, data has been made public on the prevalence of asthma as counted in Project Energize surveys from 2004 to last year.
The researchers found a drop in asthma symptoms for several demographic groups, including 7-year-old girls, European New Zealanders and those attending schools serving wealthier areas.
They also found that 17.7 per cent of the 7-year-olds were experiencing asthmatic wheezing when their parents responded to last year's survey, compared with 22.2 per cent of children aged 6 or 7 in several regions nationally when last checked in 2001-2003 as part of a multi-country survey.
That survey, published in 2008, found that although the prevalence of reported asthma in New Zealand had risen to nearly one in three for children and adolescents, there had been a reduction in the prevalence of asthma symptoms, such as "current wheeze", and also the severity of symptoms.
A researcher involved in Project Energize, Professor Elaine Rush of Auckland University of Technology, noted that its children could run 13 per cent faster than other youngsters in Canterbury.
"If they have more physical fitness and better nutrition we hope that the severity of asthma might be less because unless we have good nourishment, any disease is going to be worse. Food is your first medicine."
Professor Julian Crane, head of the Wellington Asthma Research Group at Otago University, said the Waikato findings were interesting, although the changes within Waikato over time were more informative than the comparison with the multi-region rate.
"There is evidence that exercise does help asthma control. It won't stop you getting asthma, but if you have it, exercise can improve management - so this finding is perfectly possible.
"However, an observational study like theirs can never prove it; for that you would need a randomised trial."
Dunedin respiratory physician Professor Robin Taylor agreed the Waikato findings were not conclusive, but said the significance of the difference from the multi-region rate for current wheeze was "striking".
"Lifestyle issues may be important and appear to have influenced the prevalence of asthma symptoms for the better."
How many experiencing wheezing:
17.7 per cent of 7-year-olds from Waikato schools last year
22.2 per cent of 6- to 7-year-olds from other regions 2001-03