Background: Although elevated blood pressure is associated with an increased risk of atrial fibrillation (AF), it is unclear if this association varies by individual characteristics. Furthermore, the associations between AF and a range of different vascular events are yet to be reliably quantified.

Methods: Using linked electronic health records, we examined the time to first diagnosis of AF and time to first diagnosis of nine vascular events in a cohort of 4.3 million adults, aged 30 to 90 years, in the UK.

Results: A 20-mmHg higher usual systolic blood pressure was associated with a higher risk of AF [hazard ratio (HR) 1.21, 95% confidence interval (CI) 1.19, 1.22]. The strength of the association declined with increasing age, from an HR of 1.91 (CI 1.75, 2.09) at age 30-40 to an HR of 1.01 (CI 0.97, 1.04) at age 80-90 years. AF without antithrombotic use at baseline was associated with a greater risk of any vascular event than AF with antithrombotic usage (P interaction < 0.0001). AF without baseline antithrombotic usage was associated with an increased risk of ischaemic heart disease (HR 2.52, CI 2.23, 2.84), heart failure (HR 3.80, CI 3.50, 4.12), ischaemic stroke (HR 2.72, CI 2.19, 3.38), unspecified stroke (HR 2.59, CI 2.25, 2.99), haemorrhagic stroke, chronic kidney disease, peripheral arterial disease and vascular dementia, but not aortic aneurysm.

Conclusions: The association between elevated blood pressure and AF attenuates with increasing age. AF without antithrombotic usage is associated with an increased risk of eight vascular events.