Nudging for Anticoagulation Adherence in Atrial Fibrillation

Study Design This is a prospective, randomized, parallel-group, controlled trial. A total of 84 adults with atrial fibrillation (AF) who are prescribed oral anticoagulants will be enrolled from a cardiology clinic. Participants will be randomly assigned to either the intervention group or the control group (usual care) in a 1:1 ratio using block randomization.

Intervention

The intervention group will receive a multi-component nudging program designed to support medication adherence. The program is based on behavioral economics principles (System 1 automatic processing) and includes:

A short educational video that uses vivid examples and social norms to raise awareness of stroke risk and the benefits of anticoagulation.

A personalized action plan (implementation intention) that links pill-taking to a daily routine (e.g., "after breakfast, I will take my pill").

A paper medication calendar with a check-off grid and visual cues (e.g., icons for brushing teeth or meals) to serve as an environmental reminder.

Tapered SMS reminders: 3 times/week during weeks 1-3, 2 times/week during weeks 4-6, and 1 time/week during weeks 7-8. Reminders are sent 30 minutes before the participant's chosen dosing time.

A mid-point telephone call (week 4) to address barriers and adjust the action plan if needed.

The control group will receive usual care, which includes standard discharge education and routine clinic visits. After the study ends, control participants will be given the same medication calendar and text message templates.

Outcome Measures The primary outcome is medication adherence, measured at baseline, week 8 (end of intervention), and week 12 (follow-up) using the Medication Adherence Estimation and Differentiation Scale (MEDS). MEDS is a 16-item, 5-level Likert scale that captures adherence across five dimensions: side effects, drug addiction, drug cost, lack of need/deliberate non-adherence, and unintentional non-adherence.

Secondary outcomes include:

Medication beliefs: measured by the Beliefs about Medicines Questionnaire (BMQ), which assesses perceived necessity and concerns about anticoagulants.

Illness perception: measured by the Revised Illness Perception Questionnaire in patients with atrial fibrillation（AF-IPQ-R）, a 36-item scale evaluating illness perception of atrial fibrillation.

Cost-effectiveness: assessed by collecting direct medical costs (medication, clinic visits, hospitalizations) and indirect costs (time lost, travel), combined with quality-of-life data from EQ-5D-5L to estimate incremental cost-effectiveness ratios.

Data Collection and Analysis All outcomes will be collected by a research assistant blinded to group assignment. Statistical analysis will follow the intention-to-treat principle. The primary analysis will use a mixed-effects linear model to compare changes in adherence between groups over time. Mediation analysis will test whether medication beliefs and habit strength mediate the intervention effect on adherence, using bootstrapping methods. Cost-effectiveness will be analyzed from a societal perspective.

Inclusion criteria

• Age ≥18 years

Diagnosed with non-valvular atrial fibrillation (AF) confirmed by medical records

Prescribed oral anticoagulants (e.g., warfarin, rivaroxaban, apixaban, dabigatran, edoxaban) for at least 3 months

Own a personal mobile phone capable of receiving SMS messages

Willing and able to provide written informed consent

Exclusion criteria

• Severe cognitive impairment or psychiatric disorder that would preclude completion of questionnaires or adherence to the intervention

Life expectancy <6 months due to comorbid conditions

Currently enrolled in another medication adherence intervention study

Unable to read or understand Chinese (since validated Chinese scales are used)