New evidence suggests that atrial fibrillation, in which the heart has an irregular beat, is linked to an increased risk of dementia. An irregular heartbeat speeds up the rate at which cognitive function deteriorates, but may be a way to address this, MedicalNewsToday reports. The new study paper on this topic was just published in the journal Neurology, researchers at the Karolinska Institute and Stockholm University, which are in Sweden.
In AFib, the heart’s atria–or the chambers that receive blood and then send it to the ventricles, which pump it out to the rest of the body–beat irregularly. Because of this, blood can pool inside the heart and form clots, which may later circulate to the brain, leading to a stroke.
The new study has found that AFib also increases the risk of another health problem as people age–namely, dementia. However, this warning also comes with an encouraging solution, the authors explain.
“Compromised blood flow caused by atrial fibrillation may affect the brain in a number of ways,” as study co-author Chengxuan Qiu explains. “We know [that] as people age, the chance of developing atrial fibrillation increases, as does the chance of developing dementia,” Qiu says, adding: “Our research showed a clear link between the two and found that taking blood thinners may actually decrease the risk of dementia.”
AFib is linked with faster cognitive decline
In the new study, the investigators analyzed data collected from 2,685 participants with an average age of 73. All of these participants were followed for an average period of 6 years. The team interviewed each person and administered a medical exam at baseline and then again after 6 years for participants younger than 78, or once every 3 years in the case of participants older than 78 at the beginning of the study. None of these volunteers had dementia at baseline, though 9% of all the participants (243 individuals) had been diagnosed with AFib.
Over the follow-up period, 11% of the total number of participants (279 individuals) developed AFib, and 15% of the cohort (399 individuals) received a diagnosis of dementia. After analyzing the data, the researchers revealed that the cognitive function–including thinking capacity and memory–of participants with AFib tended to deteriorate more rapidly than in the case of people with healthy cardiovascular systems.
Importantly, people with AFib had a 40% higher chance of developing dementia when compared with their healthy peers.
Of the 2,163 participants without AFib, 10% (278 individuals) were diagnosed with dementia throughout the course of the study.
As for the 522 people with AFib, 23% (121 individuals) developed dementia.
Blood thinners may counteract risk
However, the team also saw that participants with AFib who took blood thinners to prevent blood clots actually had a 60% lower risk of developing dementia, compared with those who did not take this medication.
Of the 342 people who did not take blood thinners, 22% (76 people) developed dementia, while among the 128 participants who did take blood thinners, only 11% (14 people) developed the neurodegenerative condition. At the same time, the researchers also note that participants who took antiplatelet drugs–which prevent clots from forming in the arteries-did not have a lower risk of dementia.
“Assuming that there was a cause-and-effect relationship between using blood thinners and the reduced risk of dementia,” explains Qui, “we estimated that about 54% of the dementia cases would have been hypothetically prevented if all of the people with atrial fibrillation had been taking blood thinners.” He added, “Additional efforts should be made to increase the use of blood thinners among older people with atrial fibrillation,” the researcher advises.
The investigators nevertheless admit that their study faced some limitations, such as the fact that it did not distinguish among different subtypes of AFib, or that certain participants with AFib may not have been diagnosed accordingly due to lack of symptoms.
This news really knocked me for a loop. Why? Because many of my friends have AFib but are not taking a “blood thinner.” According to the aforementioned study in Neurology, people with AFib have a 40% greater chance of getting dementia than their heart-healthy peers. That’s huge.
Of course I was skeptical about who funded the study thinking there must be a drug company with a blood thinner to sell somewhere in the picture, but I was wrong. The study was funded by the Swedish Ministry of Health and Social Affairs and the Swedish Research Council.
Lead author Mozhu Ding, of the Karolinska Institute in Stockholm, disclosed support from the China Scholarship Council, Konung Gustaf V:s och Drottning Victorias Frimurarestiftelse, Lindhés Foundation, Gamla Tjänarinnor, and National Graduate School on Ageing and Health. Co-authors disclosed support from the Swedish Research Council for Health, Working, Life and Welfare and the Swedish Research Council.
So, how scared should we actually be about these frightening statistical data with so many people apparently at risk for the onset of dementia due to AFib?
“Subclinical cerebral infarcts could contribute to the association between AFib and cognitive decline,” noted Luciano Sposato, MD, of Western University in London, Ontario, Canada and Lin Chen, MD, of the University of Minnesota in Minneapolis, in an accompanying editorial.
A brain infarction is when the brain is prevented from receiving blood, leading to tissue damage, stroke, and possible fatality. So there’s a distinct possibility that AFib alone isn’t always to blame for cognitive decline.
Well, I dug a little deeper and learned that the situation may not be as dire as it looks on a first pass.
MedPageToday points out that researchers admittedly have struggled to show a definite benefit of anticoagulants for dementia prevention in AFib patients: a randomized controlled trial may be unethical because of the substantial risk reduction in ischemic stroke associated with anticoagulation. That leaves observational studies, which are prone to bias, including confounding (unplanned factors) by indication.
“Patients with cognitive impairment are less likely to be prescribed oral anticoagulants, probably because of the physician’s perceived risk of potential noncompliance or because of potential patients’ medication errors,” Sposato and Chen observed.
And unlike a cerebrovascular event, identifying a clear time of dementia onset can be challenging. Unmeasured confounding is a major shortcoming of this study, which possibly resulted from the limited number of variables in propensity-matched regression analyses, they added.
Ding and colleagues reported other limitations: they could not distinguish between AFib subtypes, and the Mini Mental State Examination (MMSE) might have underestimated cognitive decline. The study included mostly highly educated Caucasians from an urban district and findings may not apply to other populations.
Clearly, dementia is extremely worrisome because its largest subclass is Alzheimer’s disease, for which there is no cure. Although the Swedish study’s findings are both problematic, yet mitigated by the potential benefit of blood thinner dosing, I will be spreading the word amongst my friends and colleagues who have AFib that there likely is a connection with early onset of dementia. And make certain our healthcare providers are aware of this study.