Good prognosis for patients with mild asthma
medwireNews: Research findings can reassure patients with mild asthma that the long-term prognosis is good, with only a tenth of patients transitioning to more severe disease over 10 years.
Older age at asthma onset and inappropriate use of rescue medications – either excessive doses of acute reliever medications or inadequate doses of controller medications – were associated with an increased risk for transition, say Mohsen Sadatsafavi (University of British Columbia, Vancouver, Canada) and colleagues.
“There is a pressing need for clinicians to consider regular use of low-dose inhaled corticosteroids [ICS] in patients with mild asthma who require frequent rescuer therapy,” they stress.
A total of 70,829 patients with incident mild asthma, aged an average of 31 years, were identified from the administrative health data of British Columbia. On an annual basis over the 10 years of follow-up, each participant’s asthma severity was characterized as mild/dormant, moderate, or severe.
This was determined by the intensity of asthma medication use. Mild asthma was based on ICS use of up to an average of 500 µg/day of beclomethasone equivalent or 250 µg/day if receiving additional controller medications, needing no more than three doses per week of short-acting beta agonists (SABA), and no moderate-to-severe exacerbations requiring hospitalization, emergency room visit, or use of an oral corticosteroid.
Severe asthma was defined by the use of more than 1000 µg/day of an ICS or the presence of difficult to control asthma, with at least 10 doses a week of a SABA and experiencing at least one moderate-to-severe exacerbation.
Patients who had asthma medication use between the two and did not meet either the mild/dormant asthma or severe asthma criteria were classified as having moderate asthma.
The majority of patients, at 91.6%, continued to have mild asthma during the following 10 years, whereas 8.4% transitioned to more severe asthma – 6.7% to moderate asthma and 1.7% to severe asthma – by the end of follow-up.
“The proportion of patients transitioning to moderate and severe asthma […] slowly increased over time,” the researchers note in The Journal of Allergy and Clinical Immunology: In Practice.
Baseline factors that significantly increased the risk for transitioning to more severe asthma included inappropriate use of rescue medications, which was seen in 12% of patients, comorbidity, and older age, with respective odds ratios of 1.79, 1.07 to 1.25 (Charlson comorbidity index [CCI] score of 1–3 vs 0), and 1.24 (per 10-year increase).
By contrast, ICS and long-acting beta agonists (LABA) combined versus ICS monotherapy was associated with a significantly reduced risk for transitioning to more severe asthma, with an odds ratio of 0.92, while allergic rhinitis was not associated with transitioning.
Sadatsafavi and colleagues note that some of these factors are “potentially modifiable, signaling an opportunity for preventing adverse asthma outcomes through risk factor management and treatment.”
Indeed, they plotted 10-year trajectories of mild asthma according to these risk factors and found that for every 1000 patients, inappropriate SABA use compared with appropriate use would lead to 38 (4%) extra patients transitioning to more severe asthma. The corresponding figures would be 38 (4%) for 40-year-olds versus 20-year-olds, 15 (2%) for those with CCI scores of 1 or above relative to no comorbidities, and eight (1%) for the use of ICS monotherapy compared with ICS/LABA combination therapy.
The team concluded: “Because mild asthma represents most patients with asthma, focusing on modifiable factors that prevent its transition to severe states over time can provide substantial population-level benefits.”
By Lucy Piper
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