Wide geographical variations in rates of difficult-to-treat asthma in Australia have been revealed by a ‘heatmap’ study showing high rates of corticosteroid use among people living in regional areas of WA and country New South Wales.
Professor Peter Wark’s analysis of 2018-2019 PBS data found 48% of people living with asthma in central and southern Western Australia had difficult-to-treat asthma, followed by 43% in central and southern parts of NSW, and 30% across northern parts of the Northern Territory.
Difficult-to-treat asthma was defined as having two or more high-dosage inhaled corticosteroids, and long-acting beta-agonist prescriptions within six months. Across the country, about 24% of the 1.85 million people living with asthma were characterised as having difficult-to-treat condition, with prevalence ranging from 14% to 48%.
Further, between 26% and 67% of people with difficult-to-treat asthma were deemed to have “uncontrolled” asthma, significantly higher than international figures, after receiving four or more high-dose medications.
Professor Wark, a chief investigator in the NHMRC Centre of Excellence in Severe Asthma, Hunter Medical Research Institute, Newcastle NSW, said there was “clearly a lot of variation”.
“The million-dollar question is why is there that variation and I don’t think there is a single answer to that question either,” he told the limbic.
“There clearly does appear to be a signal that people in rural and remote areas overall are really in the group who are using a lot of corticosteroids.”
He said the results indicated the system of prescription of oral corticosteroids should be considered.
“We should consider how we are allowing oral corticosteroids to be prescribed and dispensed,” he said. “At the moment prescription allow up to 60 tablets and four repeats. This is a huge number of tablets and should be required by very few people with asthma.
“Options that limit smaller volumes of medications to reflect short courses for exacerbations or that flag the number of prescriptions being used back to the prescriber would safely limit use and flag those at most risk.”
Professor Wark noted there were also pockets of high corticosteroid use in urban areas, and said it may represent socioeconomic impacts as well as access to healthcare and specialist care, geographic and environmental factors.
The high use of oral corticosteroids in some communities, he said, reflected suboptimal asthma control, but also increased a burden of illness associated with increased risk of infection, osteoporosis and cardiovascular disease.
“Despite all the things we do with asthma, we still have quite a large proportion of people who require the use of oral corticosteroids,” he said. “That’s is something we should be working towards reducing, if not minimising as much as we possibly can.”
The study, published in the Journal of Asthma, drew on dispensing data from 81.8% of Australian pharmacies, cross-referencing deidentified patient data with prescription medicines for chronic airway obstruction. It screened out long-acting muscarinic agonists alone or with concomitant long-acting beta-agonist to exclude people with chronic obstructive pulmonary disease.
Oral corticosteroid exposures were analysed for cumulative exposure of more than 1g over six months. The data was then matched to ABS statistics areas to produce the prevalence heatmaps.
The analyses revealed 1,851,129 individuals could be classified as living with asthma. Of these, 440,800 (24%) patients with asthma had difficult-to-treat asthma, and 96,338 (22%) had uncontrolled disease based on their oral corticosteroid use.
Western Australia recorded high rates of difficult-to-treat asthma, ranging from 22% in the lowest statistical area to 48% in the highest. In NSW, the highest prevalence was 43%, while two local areas in Tasmania recorded 31%. The lowest rates were recorded in Queensland (14% in the lowest local area), NSW (14%), Queensland (15%), and Victoria (18%).