Asthma causes remain a mystery

By MARTIN JOHNSTON and ANGELA GREGORY

The number of people with asthma is expanding explosively, but researchers are without answers to what causes the disease.

A Herald series this week has shown how asthma is widely mismanaged in New Zealand and has failed to make it into the top rank of Government health priorities.

One in six people in New Zealand has asthma. It is the most common cause of children's hospital admissions and the number of sufferers is expected to rise by half in the next 10 to 15 years.

It costs the country an estimated $825 million a year - $125 million in direct medical costs and $700 million for indirect costs including days of work lost.

Asthma prevalence is highest in Western countries, giving weight to the "hygiene hypothesis", one of the leading theories on the causes of the disease.

It suggests that as life in the West has become more hygienic and the rate of childhood infections has declined, people's immune systems have been primed to become allergic to otherwise harmless substances such as minute dust-mite faeces.

What is known is that an asthmatic's symptoms can be triggered by a huge range of substances and conditions, from cat fur to cigarette smoke and a change in the weather. Researchers can offer little advice on how to prevent people developing asthma, but some have found a diet rich in plant-based foods may be protective.

Drug companies, lung doctors and asthma groups say access to newer types of inhaled drugs to prevent and control symptoms is too restrictive.

Dr Jeff Garret, clinical director of medicine at Middlemore Hospital, said asthmatics paid 25 to 30 per cent of their own treatment costs in New Zealand, compared with 5 to 10 per cent in Australia and Britain. Consequently, New Zealand's hospital admission rate for asthma treatment was among the world's highest.

Asthma and Respiratory Foundation medical director Professor Ian Town said New Zealand was complacent about asthma, because the disease's falling death rate created the mis-perception that it was being well managed.

But the high rate of hospital admissions and the 550,000 school days lost a year revealed the true picture.

Asthma New Zealand executive director Gerry Hanna said 25 per cent of Auckland asthmatics were without a GP, partly because of the cost. "That's why they come here [to local asthma societies], because we're free. They're looking to us to prescribe, but we can't."

Some jobs can cause breathing problems: 20 per cent of asthmatics suffer symptoms associated with their work. Jobs ranging from welding to seafood processing have been found to trigger asthma symptoms.

The Council of Trade Unions fears workers have not been told of their rights to compensation for occupational illnesses, which can include asthma.

Air pollution is a known asthma trigger and the Auckland Regional Council this week renewed pressure on the Government to lower pollutants in diesel and petrol.

nzherald.co.nz/health