Oral anticoagulants are associated with a significant reduction in the risk of dementia in patients with atrial fibrillation (AF), according to a study published in the European Heart Journal (online, 24 October 2017)
The retrospective study examined data from all patients (444,106) in Sweden with a hospital diagnosis of AF and no previous diagnosis of dementia between 2006 and 2014.
When the patients were analysed according to the treatment they were taking when enrolled in the study, it was found that those patients assigned anticoagulant treatment to reduce their risk of stroke had a 29% lower risk of dementia than patients not taking anticoagulant treatment.
In an analysis of the events that happened while patients were on anticoagulant treatment, the researchers found a 48% reduction in the risk of dementia compared with those who did not take anticoagulants.
Patients who developed dementia were found to be older and had more comorbidities than patients who did not develop dementia. The researchers concluded that absence of oral anticoagulant was an independent risk factor for dementia, along with age, Parkinson’s disease and alcohol abuse.
“Our study showed a strong relationship between absence of anticoagulant treatment and dementia when analysed according to medication at baseline, which became even stronger when we took the actual exposure of anticoagulants during the study period into account,” said Leif Friberg, associate professor in cardiology at the Karolinska Institute and author of the study.
“We used all available methods to adjust for cofactors, and even for the detection of hidden confounding,” he said, adding that although a randomised control trial would prove or disprove a causal relationship, such a study could not be carried out due to ethical reasons.
“You can’t give patients with atrial fibrillation and risk of stroke placebo in order to see if they develop dementia or not.
“I am as certain as one can be within the limitations of a retrospective observational study, that we have detected a causal relationship.”
In addition, no difference in risk reduction was found between warfarin and newer oral anticoagulants.
According to Friberg the results are important because patients frequently stop taking their anticoagulant drugs.
“In Sweden, we are getting pretty good at starting patients on anticoagulants when they get their diagnosis, but then 10–15% drop off from treatment each year.”
“If patients (and doctors) were made aware of [the link between anticoagulants and dementia] I am convinced that far more patients than now would hang on to their protective treatment.”