Adherence to asthma medication over time important for improving symptom control

In a new study, novel metrics showed that lower time adherence to asthma controller medications was associated with greater risk for decline in asthma symptom control.

“We currently have very simplistic ways to estimate how well an asthma patient takes their daily medication, based on averaged dosage taken over a period,” Cindy Thamrin, PhD, associate professor and principal research fellow at the University of Sydney and research leader of the Airway Physiology and Imaging Group, told Healio. “Working together with Helen Reddel, MD, PhD, we wanted to be able to capture specific aspects of medication taking, eg, skipping doses vs. taking less medication, and discovering if there are any patterns over time.”

For the retrospective analysis, the researchers used data on asthma controller medication adherence from a previously published cluster-randomized controlled trial of 143 patients with poorly controlled asthma despite treatment with a moderate-high dose of inhaled corticosteroid and long-acting beta agonist. The researchers calculated several novel metrics from the first 2 months of the study, including the “time adherence,” which captures cumulative gaps in adherence over time. The researchers then compared these patients in terms of symptom control and risk for asthma exacerbations over the 6-month study period.

“In this study, we used novel data analytics to capture patterns in daily medication-taking among patients with mild to moderate asthma. We found that taking medication faithfully over a cumulated period of time, rather than simply taking more medication, was more important for improving symptom control over 6 months,” Thamrin said.

Based on adherence metrics, the researchers identified two main patient clusters; one cluster included patients with high time adherence (n = 75) and the other cluster included patients with low time adherence (n = 23). Although both patients with high and low time adherence had similar asthma symptom control at the start of the study, patients with high time adherence had a lower subsequent decline in the Asthma Control Test score over 2 to 6 months (score, 1 vs. – 2; P = .012) and had better asthma symptom control by 6 months (score, 20 vs. 17; P = .034).

The researchers reported no significant differences in the proportion of patients with high and low time adherence with asthma exacerbations or time to asthma exacerbation.

“We weren’t able to show a difference in the rate of asthma attacks, but this may not be surprising because we only had a small dataset to work with,” Thamrin said. “What is interesting is that our previous work in patients with difficult-to-treat asthma showed that it was the irregularity of medication dosage-taking which related best to symptoms, suggesting that optimum medication-taking behavior may differ among patients with different types of asthma. Thus, these novel metrics will allow us to discover different types of medication-taking behavior and how they affect the patient’s asthma.”

The researchers noted several limitations of the study, including its modest sample size and potential for overestimation of adherence in a real-world scenario.

“These are small proof-of-concept studies, which need to be validated in larger data sets, as well as in other asthma populations,” Thamrin said. “This is something we are currently working on.”

Editor’s note: This article was updated on Jan. 24, 2022, with additional information from the authors.

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Cindy Thamrin, PhD, can be reached at cindy.thamrin@sydney.edu.au.