Patients with atrial fibrillation (AFib) who are treated with blood thinners are at a significantly reduced risk for developing dementia, according to research published Oct. 24 in the European Heart Journal. Individuals on oral anticoagulants (OACs) at baseline demonstrated a 29 percent lower risk of dementia compared to those not on blood thinners, while people treated with OACs throughout the study experienced a 48 percent risk reduction.
The study analyzed 444,106 patients diagnosed with AFib in Sweden between 2006 and 2014 who had no previous history of dementia. It included more than 1.5 million patient-years of follow-up, during which 26,210 patients received a new diagnosis of dementia. The strongest predictors of dementia were older age, Parkinson’s disease, absence of OAC treatment and alcohol abuse.
AFib increases the likelihood of stroke and dementia, and OACs have been shown to reduce the risk of stroke. However, the association between OACs and dementia risk in AFib patients was unclear when this study was undertaken, according to its authors. But they predicted there would be a connection.
“If OAC protects against large emboli which causes stroke, OAC treatment also ought to protect against small emboli which causes microinfarctions that eventually lead to cognitive deterioration,” wrote Leif Friberg, MD, PhD, and Marten Rosenqvist, MD, PhD, both with the Karolinska Institute in Stockholm.
The researchers noted the sooner OAC treatment was initiated after a diagnosis of AFib, the less likely a patient would be to develop dementia. Their findings also highlighted the importance of persistent OAC adherence.
"Patients start on oral anticoagulation for stroke prevention but they stop after a few years at an alarmingly high rate,” Friberg said in a press release. “In the first year, approximately 15% stop taking the drugs, then approximately 10% each year. In this study we found that only 54% of patients were on oral anticoagulant treatment.
“If you know that AF eats away your brain at a slow but steady pace and that you can prevent it by staying on treatment, I think most AF patients would find this a very strong argument for continuing treatment. … No brain can withstand a constant bombardment of microscopic clots in the long run.”
The study showed no difference in dementia prevention between warfarin and newer, non-vitamin K oral anticoagulants.
Friberg and Rosenqvist said their research couldn’t prove or disprove causality. In addition, some medical histories of patients were incomplete, although the authors attempted to adjust for known baseline characteristics in their analyses using propensity-score matching.