Comorbidity Associated with Atrial Fibrillation: a General Practice-based Study

Background: [corrected] Atrial fibrillation is an important risk factor for ischaemic stroke. Anticoagulation treatment with warfarin can substantially reduce the risk of stroke in people with atrial fibrillation but concerns about their side-effects have limited their use in clinical practice. However there has been little population-based research on the comorbidity associated with atrial fibrillation and on the prevalence of potential contraindications to anticoagulantion treatment among these patients.

Aim: To determine the prevalence of known risk factors for ischaemic stroke and possible contraindications to anticoagulant treatment among patients with atrial fibrillation.

Method: One-year prospective cohort study in 60 general practices in England and Wales with a total population of 502,493 people. Age and sex specific prevalence rates and relative risks of risk factors for ischaemic stroke and possible contraindications to antithrombotic treatment were calculated.

Results: The number of patients who had a diagnosis of atrial fibrillation during the year was 1,414 (0.3%) patients. The prevalence of other nsk factors for ischaemic stroke in patients with atrial fibrillation increased with age in men, from 48% (relative risk [RR] = 3.78, 95% confidence interval [95% CI] = 3.23-4.41) at 45 to 64 years to 64% (RR = 2.21, 95% CI = 2.00-2.44) at 75years and over A similar increase of 50% (RR = 4.36, 95% CI = 3.54-5.38) to 60% (RR = 2.07, 95% CI = 1.91-2.23) was seen in women. The percentage of men with atrial fibrillation with at least one contraindication to antithrombotic treatment was 5% at 45 to 64 years and 14% at 75 years and over. Among women with atrial fibrillation, 7% had a contraindication at 45 to 64 years and 16% at 75 years and over. The all-ages relative risk of a contraindication was 1.17 (95% CI = 0.92-1.48) in men and 1.53 (95% CI = 1.28-1.83) in women. Forty per cent (575) of patients with atrial fibrillation had at least one risk factor for ischaemic stroke and no contraindications to antithrombotic treatment.

Conclusion: Atrial fibrillation is associated with a substantial increase in the prevalence of risk factors for ischaemic stroke. By contrast, potential contraindications for antithrombotic treatment are more evenly distributed among patients with and without atrial fibrillation. Around 40% of patients with atrial fibrillation in primary care are at high risk of stroke and have no contraindicationsfor antithrombotic treatment.