Heterogeneity in asthma medication adherence measurement

Medication non-adherence is strongly associated with poor asthma control and outcomes. Many studies use an aggregate measure of adherence, such as the percentage of prescribed doses that were taken, however this conceals variation between patients' medication-taking routines. Electronic monitoring devices, which precisely record the date and time of a dose being actuated from an inhaler, provide the means to objectively and remotely monitor adherence behavior patterns. This secondary analysis of a New Zealand audio-visual medication reminder intervention study visually explored the relationships, variation, and heterogeneity between multiple measures of adherence, in 211 children aged 6-15 years old who presented to an emergency department with an asthma attack. Our findings highlight the weakness of statistical relationships between measures of adherence, and the irregularity in patient medication-taking behavior. This demonstrates that a single aggregate adherence measure fails to detect asthma patients for whom their day-to-day medication taking (implementation) is inconsistent with their longitudinal medication taking (persistence).