Background/Aims: Dabigatran is widely used for stroke prevention in atrial fibrillation (AF), but its effectiveness in patients with class III obesity (body mass index [BMI] ≥ 40kg/m²) remains uncertain. We evaluated whether BMI modifies the association between dabigatran use and risk of ischaemic stroke (IS) or transient ischaemic attack (TIA) in a multiethnic New Zealand population.
Methods: We conducted a retrospective nested case-control study. Cases with incident IS/TIA were identified from the fifth Auckland Regional Community Stroke Study (ARCOS V - 1st September 2020–31st August 2021), with event-free controls randomly selected from the National Minimum Dataset. Multivariable logistic regression was used to estimate adjusted odds ratios (aORs) for IS/TIA. Effect modification by BMI (<30, 30-39.9, ≥40 kg/m²) was assessed using an interaction term.
Results: Among 1,854 patients with AF (295 cases, 1,559 controls), dabigatran use was associated with lower odds of IS/TIA (aOR 0.50, 95% CI 0.38–0.68). BMI was not independently associated with IS/TIA after adjustment. The association between dabigatran use and lower IS/TIA risk was directionally consistent across BMI categories, including BMI ≥40 kg/m², although estimates in this subgroup were imprecise. There was no statistical evidence of interaction between dabigatran use and BMI (p=0.49).
Conclusion: Dabigatran use was associated with reduced odds of IS/TIA across BMI categories. However, limited precision in patients with class III obesity means clinically important differences in this subgroup cannot be excluded.