Terry Quinn is the joint Stroke Association & Chief Scientist Office Senior Clinical Lecturer based in the Institute of Cardiovascular and Medical Sciences, University of Glasgow. In this blog Terry discusses his recent Age and Ageing paper looking at anticoagulants (blood thinners) and dementia. He tweets @DrTerryQuinn
Despite decades of research, an effective treatment to prevent or delay dementia remains elusive. This is in stark contrast to cardiovascular disease, where we have many evidence based treatments in the therapeutic toolbox. Certain cardiac diseases seem to be associated with cognitive decline and this begs the question, could cardiovascular medications prevent dementia?
We decided to look at a particularly common cardiac condition, atrial fibrillation (AF, an irregular heart beat). People with AF are at risk of stroke, a risk that can be substantially reduced with anticoagulant medication. People with AF are also at risk of dementia. In this project we wanted to describe the cognitive effects of anticoagulants in AF. In theory anticoagulants could reduce cognitive decline by preventing strokes, both strokes that are clinically apparent and so called “silent” strokes that are often only detected on brain scans. However, we also know that in some dementias brain blood vessels become abnormal with a propensity to bleed. Thus, an equally plausible theory would be that anticoagulants hasten cognitive decline by causing intracerebral haemorrhage.
We collated all published studies of anticoagulation in AF that included some measure of cognition or dementia. Papers describing dementia and AF were available in cardiology, neurology and psychology journals and so we had to “throw the net wide” to ensure we didn’t miss any relevant studies. We also contacted researchers working in the area and the manufacturers of anticoagulants to see if they knew of any studies we had not found.
The ideal study design to answer questions around anticoagulation and dementia, would take a group of people with AF and no dementia, randomly allocate some to receive anticoagulation and others to receive a placebo, and assess both groups for dementia several years later. We found several studies of anticoagulation in AF that also collected information on dementia. Unfortunately almost all did not report their findings in a way that allowed us to specifically look at the effects of anticoagulant medication. In the end, 19 papers were suitable for our analysis. Only one of these studies was close to our ideal study design.
Accepting the limitations, when we summarised the results of the available papers there were still some intriguing findings. In studies that looked at development of dementia, there was no sign of decreased or increased dementia rates in those taking anticoagulants. However, patients treated with anticoagulants had better scores on a memory tests than patients given alternative medications (usually aspirin). The difference in memory test scores was small and it is debatable whether it would be of any clinical significance to the individual.
So what have we learned from this study. The available studies are not perfect, but they do suggest that anticoagulants may have an effect on cognition. More broadly speaking, our study does suggest that treating cardiovascular disease may have beneficial cognitive effects. There is a need for large, well conducted studies looking at dementia and anticoagulation and the many other cardiovascular treatments.
Read his Age & Ageing paper Thromboprophylaxis in atrial fibrillation and association with cognitive decline: systematic review
Terry’s research is supported by a Stroke Association programme award; the work presented in this paper was supported by a British Geriatric Society Summer Scholarship awarded to Peter Moffitt.