Atrial fibrillation, an irregular heartbeat, is the most common heart rhythm disorder in daily clinical practice with about 33.5 million people with atrial fibrillation worldwide. This heart rhythm disorder has been associated with cognitive impairment and/or dementia.
Cognitive impairment refers to a decrease in functions such as learning, memory, and decision-making, which is greater than expected in the normal process of ageing. Dementia refers to memory loss, decision-making difficulties, and/or learning difficulties, which gradually become worse over time and that significantly affects daily life.
People with atrial fibrillation have a 5 times higher risk of suffering stroke, a blockage of blood flow to portions of the brain, often caused by blood clots. Thus, people with this irregular rhythm are often prescribed a type of medication called anticoagulants, which reduces the change of blood clots forming in the heart that might then travel to the brain and cause stroke. People with atrial fibrillation and stroke have twice risk of suffering from cognitive impairment and/or dementia compared to people without atrial fibrillation or stroke.
The relationship between atrial fibrillation, cognitive impairment, and/or dementia is not well understood. Research on people who have not had a stroke has shown that use of an anticoagulant may decrease the occurrence of dementia, but this research only focusses on people with dementia and not those with cognitive decline.
This study will investigate the association between atrial fibrillation, cognitive impairment and/or dementia, and the effect of anticoagulant (antithrombotic) therapy.
Technical summary
In the United Kingdom (UK), there are approximately 11.9 million people aged 65 and over. With a prevalence of 1.985%, about 1.2 million (10%) of them have atrial fibrillation. In addition, there are between 0.6 and 2.4 million people with cognitive impairment and around 850,000 with dementia people in the UK.
Research suggests that there may be a link between atrial fibrillation and increased risk of cognitive impairment and/or dementia. There is some evidence that antithrombotic therapy (aspirin, warfarin, non-vitamin K antagonist oral anticoagulants (NOACs)etc.) used to prevent stroke in people with atrial fibrillation may help to avert and/or reduce the development of, and progression of, cognitive impairment. However, there are very few studies that have examined the link between atrial fibrillation and cognitive decline and the impact of anticoagulation on this relationship, and most have looked at small samples or samples that might not be representative.
Our study will use the Clinical Practice Research Datalink (CPRD), which is a representative sample of the primary care population in England. We will extract information on a sample of adults aged over 65 years. We plan to use this database to investigate the following research questions: (1) Is there a higher risk of cognitive impairment and/or dementia for people with atrial fibrillation? and (2) Does the use of antithrombotic therapy reduce the risk of cognitive impairment and/or dementia for people with atrial fibrillation?
Hazard ratios of the association between atrial fibrillation, cognitive impairment and/or dementia, overall and stratified by antithrombotic therapy (anticoagulants and antiplatelets), stroke risk determined with the CHA2DS2-VASc score, Charlson Comorbidity Index, and Frailty Index will be estimated using Cox regression. Sensitivity analyses will be performed excluding patients who are taking antidepressants as depression may represent a prodrome of dementia and with a history of stroke.
1. Cognitive impairment. It will be defined by Read medical codes, with no recording of identified Alzheimer’s disease on or before the date recording the mild cognitive impairment.
2. Dementia. It will be defined using Read medical codes, with no recording of an identified non-Alzheimer’s disease or non-vascular cause of dementia on or before the date when dementia was recorded.
Deirdre Lane - Chief Investigator - University of Liverpool
Jose Ignacio Cuitun Coronado - Corresponding Applicant - University of Liverpool
Deirdre Lane - Collaborator - University of Liverpool
Gregory Lip - Collaborator - University of Liverpool
Iain Buchan - Collaborator - University of Liverpool
Pieta Schofield - Collaborator - University of Liverpool
Stephanie Harrison - Collaborator - University of Liverpool
HES Admitted Patient Care;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation