New Zealand-led research on asthma treatment is being called a "game changer" for stopping mild asthmatics from having severe attacks, an author of the study says.
The four-country study conducted by the Medical Research Institute of New Zealand was published in the New England Journal of Medicine.
It involved 675 people who had been taking medication to relieve their symptoms, and divided them into three groups: one just using a reliever inhaler when they had symptom, one using preventer and reliever inhalers and one using a combined preventer-reliever inhaler only when they had symptoms.
Study co-author Richard Beasley said the third group had half the risk of a severe attack compared to using the reliever inhaler alone.
"What this does is when a patient is having worse asthma, and they're taking more of their reliever, they're actually getting more of their preventer at the same time.
"And this turns off the asthma attack before it becomes severe."
Prof Beasley said a single inhaler would make life simpler for adults with mild asthma who would not have to take medication when they did not need it.
"It doesn't require patients to take a preventer inhaler twice daily even when they have no symptoms.
"It also addresses two key problems in asthma management; the reluctance of doctors to prescribe regular preventer inhaler therapy and the reluctance of patients to use it when they feel well."
He said pharmaceutical firms would have to work on combinations of medications, and more studies would be needed on children.
About 10 percent to 15 per cent of the world's adult population suffer from asthma, and the prevalence is high in New Zealand - one in every six adults live with the disease.