People being treated for both atrial fibrillation and Alzheimer's disease showed modestly slower cognitive decline when taking newer blood thinners rather than the decades-old drug warfarin, according to a large Swedish registry study published this week. The research, led by scientists at Karolinska Institutet and published in the European Heart Journal, is among the largest efforts yet to examine how anticoagulant choice relates to memory and thinking in patients who have both conditions.
Researchers drew on SveDem, Sweden's national dementia registry, to track 7,308 people diagnosed with both atrial fibrillation and Alzheimer's. They compared cognitive test scores — measured with the standard Mini-Mental State Examination, or MMSE — among patients taking newer non-vitamin K anticoagulants (NOACs), those on warfarin, and those on no blood thinner at all. Patients on NOACs declined roughly 0.2 MMSE points per year more slowly than those on warfarin or no treatment. NOAC use was also associated with lower rates of death, stroke, blood clots and fractures compared with no anticoagulant; warfarin showed similar benefits on those outcomes but carried a higher risk of major bleeding.
An association, not proof of cause
The researchers were careful to frame the result as a correlation, not a demonstrated cause-and-effect. Because the study was observational — following real-world patients rather than randomly assigning them to a treatment — it cannot rule out that healthier patients were simply more likely to be prescribed NOACs in the first place, or that other unmeasured factors explain the gap. Patients also could have switched medications during the follow-up period, further complicating the picture. A 0.2-point annual difference on the MMSE, a 30-point scale, is also small in absolute terms, though the authors note it could compound meaningfully over several years.
"There are reasons to believe that the treatment could have a positive effect on cognition, for example by improving blood flow and reducing small-scale damage in the brain."
Maria Eriksdotter, Professor, Karolinska Institutet
Atrial fibrillation and Alzheimer's disease frequently occur together in older adults, and doctors have long faced a difficult balance in treating both: anticoagulants cut stroke risk in patients with irregular heartbeats, but clinicians sometimes hesitate to prescribe them for people with dementia because of fall and bleeding concerns. If the cognitive benefit associated with NOACs is confirmed, it could tip that calculation further in favor of treatment rather than against it.
The authors are calling for randomized controlled trials to test whether the association reflects a genuine protective effect, since registry data alone cannot settle the question.
