Effect of hypertension duration and blood pressure level on ischaemic stroke risk in atrial fibrillation: nationwide data covering the entire Korean population

Aims There are a paucity of data on the association of duration of hypertension and blood pressure (BP) level with risk of ischaemic stroke in patients with atrial fibrillation (AF). Our objective was to investigate the association between duration of hypertension and secondly, BP levels with risk of ischaemic stroke among patients with AF. Methods and results A total of 246459 oral anticoagulant-naive non-valvular AF patients were enrolled from Korea National Health Insurance Service (NHIS) database (2005-2015). The risk of ischaemic stroke according to the duration of hypertension and systolic BP (SBP) levels were assessed. One-year increase of hypertension duration continuously increased the adjusted risk of ischaemic stroke (95% confidence interval 1.07-1.09) until 7 years, and reached a plateau with adjusted hazard ratio of 1.6. Risk of ischaemic stroke increased linearly with the increase of hypertension duration in patients younger than 65years of age, whereas the risk reached a plateau in patients aged 65years or older. In all baseline and pre-AF average SBP subgroups, longer duration of hypertension before AF was associated with higher ischaemic stroke risk than shorter duration of hypertension (all P-values for trends <0.01). However, the effect of long-term hypertension was not observed in patients with strictly well-controlled pre-AF average SBP of less than 120mmHg. Conclusion The increase of hypertension duration was associated with the increased risk of ischaemic stroke. However, this long-term effect of hypertension duration can be attenuated by long-term strict SBP control throughout the entire duration of hypertension.