Low adherence to controller medications and the preventable burden of asthma

Zafar Zafari, PhD student at the Centre for Clinical Epidemiology and Evaluation

Low adherence to controller therapies is an important contributor to the fact that asthma remains uncontrolled in a large proportion of patients—despite the fact that for most patients, effective and inexpensive controller therapies are readily available. Evidence-based strategies towards improving adherence to asthma therapies have been advocated as a means of reducing the burden of this common chronic disease.

However, to what extent such strategies can be beneficial has not yet been rigorously studied.

In a study recently published in The Journal of Allergy & Clinical Immunology (JACI), “Economic and health impact of full adherence to controller therapy in adults with uncontrolled asthma: a simulation study” Zafar Zafari and colleagues attempted to quantify the extent of the asthma burden that can be attributed to low adherence. The authors created a computer model of asthma that simulated a representative cohort of adults with uncontrolled asthma in the US. Individuals were followed for ten years in the model, and their future level of asthma control, rate of exacerbations, as well as costs and quality of life were predicted under different scenarios. These scenarios included when the current “real-world” level of adherence remains the same for the future, when all patients have achieved full adherence, and when a hypothetical adherence intervention with a given annual cost and effectiveness profile is implemented.

The model predicted that while assuring full adherence to controller therapies will increase the total costs of asthma, it will be associated with a significant improvement in quality of life, and with a more than 30% reduction in person-time with uncontrolled asthma and the rate of asthma exacerbations. In terms of the cost-effectiveness thresholds for adherence intervention programs, the authors concluded that if the value of one healthy year is $100,000, an adherence intervention should cost no more than $100 per year for each 10% improvement in adherence in order to be cost-effective.

The current study leaves no doubt that there is a tremendous care gap in asthma due to low adherence, resulting in a preventable economic and health burden. This study should be a reminder to clinicians and patients of the missed opportunities in improving asthma outcomes due to low adherence. On the other hand, this study also shows that potential adherence interventions have to meet strict cost and effectiveness thresholds to be of value to society. Investigators and policy makers should be aware of such thresholds, and carefully evaluate the cost-effectiveness of potential adherence interventions before their large scale implementation.

The authors of the paper are Zafar Zafari, J Mark FitzGerald, Larry Lynd, and Mohsen Sadatsafavi