Dabigatran Persistence and Adherence in New Zealand: a Nationwide Retrospective Observational Study

Objective: To determine the effect of age and gender on persistence and adherence in patients taking dabigatran for atrial fibrillation.

Design: A retrospective observational study over 4 years using refill prescription data from the National Pharmaceutical Database.

Setting: All patients in New Zealand who received dabigatran from July 2011 to September 2015.

Population: 43 339 people filled at least one prescription of dabigatran.

Main Outcome Measures: The proportion of patients with good adherence (treatment available at least 80% of the time), and the proportion at risk of thrombosis (a break in treatment of more than 2 days) measured 6-monthly for 3 years. Medication persistence recorded over 3 years.

Results: Persistence was highest in older patients and showed a significant correlation with age (p<0.001); 24% over 70 years had discontinued treatment by 6 months compared with 50% under 50 years. Adherence was highest in the elderly (p<0.001) with 90% of patients over 80 years with good adherence at 12 months compared with 70% in patients aged 50-60 years and less than 60% in those under 50 years. The time at risk of thrombosis showed a similar pattern with 25% below 60 years with inadequate anticoagulation more than 20% of the time. Adherence dropped during the first 18 months of treatment with the most marked fall in those under 50 years. Adherence shows that breaks in treatment are common with 30% of men under 60 years with a break in treatment of at least 28 days during the first 12 months.

Conclusion: Adherence and persistence correlate with the patient's age. Those over 70 years have high adherence consistent over time whereas younger patients have significantly worse adherence which declines over the first 18 months, with the lowest rate in those under 50 years. Adherence in our study is lower than reported in clinical trials, therefore the benefit of dabigatran in stroke prevention may not be realised in clinical practice especially in younger patients.