Usual blood pressure, atrial fibrillation and vascular risk: evidence from 4.3 million adults

Abstract

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.

Keywords: Atrial fibrillation; blood pressure; cardiovascular disease; epidemiology.

Figure 1

Adjusted hazard ratios of systolic blood pressure and diastolic blood pressure for incident atrial fibrillation by age. Adjustments were for BMI, smoking status, sex, baseline diabetes and the interaction between age as a categorical variable and systolic and diastolic blood pressures as categorical variables, respectively (plotted). Confidence intervals are displayed as floating absolute risks with no reference category. Area of each square is proportional to the inverse variance of the estimate. Hazard ratios for each category are displayed relative to the reference category (individuals aged 30-40 with usual SBP < 115 mmHg). As a result, individuals aged 80-90 are at approximately 128 times the risk of AF compared with individuals aged 30-40 years.

Figure 2

Adjusted hazard ratios of 20 mmHg higher usual SBP for incident atrial fibrillation stratified by patient subgroup. Adjustments were for age, BMI, smoking status, sex and baseline diabetes. For subgroups of age, adjustment was also for age category and the interaction between systolic BP and age category (plotted). For subgroups of sex, adjustment was also for the interaction between sex and systolic BP (plotted). For subgroups of BMI, adjustments were also for BMI category and the interaction between systolic BP and BMI category (plotted). Area of each square is proportional to the inverse variance of the estimate.

Figure 3

Adjusted hazard ratios of baseline atrial fibrillation for nine different vascular events. Adjustments were for age, BMI, smoking status, sex, baseline diabetes, baseline antihypertensive use, baseline lipid-lowering drug (statin) use, baseline anticoagulant usage, baseline antiplatelet usage and baseline atrial fibrillation (plotted). Restricted to (A) fatal and non-fatal vascular events; and (B) only fatal vascular events. Area of each square is proportional to the inverse variance of the estimate.

Figure 4

Adjusted hazard ratios of baseline atrial fibrillation for nine different vascular events. Adjustments were for age, BMI, smoking status, sex, socioeconomic status, baseline diabetes, baseline antihypertensive use, baseline lipid-lowering drug (statin) use, baseline anticoagulant usage, baseline antiplatelet usage and the interaction between baseline atrial fibrillation and baseline anticoagulant or antiplatelet use (plotted). Restricted to: (A) fatal and non-fatal vascular events; and (B) only fatal vascular events. Area of each square is proportional to the inverse variance of the estimate.

Figure 5

Adjusted hazard ratios of baseline atrial fibrillation for stroke, ischaemic heart disease and heart failure. Adjustments were for age category, interaction between continuous age and age category, BMI, smoking status, sex, baseline diabetes, baseline antihypertensive use, baseline lipid- lowering drug (statin) use and the interaction between baseline atrial fibrillation, age category and baseline anticoagulant/antiplatelet usage (plotted). Area of each square is proportional to the inverse variance of the estimate.