These blood thinners may have an unexpected benefit for Alzheimer’s patients

Atrial fibrillation is a common heart rhythm condition in older adults and also affects many people living with Alzheimer's disease. Doctors often prescribe blood thinners to these patients to reduce the chance of blood clots and stroke. Earlier research has suggested that anticoagulant treatment may lower the risk of developing dementia, but far less is known about whether these drugs influence cognitive decline after Alzheimer's disease has already been diagnosed.

"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," says Maria Eriksdotter, professor at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, and senior consultant in geriatric medicine at Karolinska University Hospital, who led the study.

Comparing Newer and Older Blood Thinners

Researchers analyzed information from SveDem (Swedish Register for Cognitive Disorders/Dementia), a national quality registry, and included 7,308 people diagnosed with both atrial fibrillation and Alzheimer's disease.

Participants were placed into three matched groups. One group received newer anticoagulants known as NOACs, another was treated with the older blood thinner warfarin (Waran), and the third did not receive any anticoagulant medication.

To track changes in thinking and memory over time, researchers used the standardized Mini-Mental State Examination (MMSE).

Slower Cognitive Decline With NOACs

People taking NOACs showed a significantly slower decline in cognitive function than those treated with warfarin or those who received no anticoagulant medication.

The difference amounted to slightly more than 0.2 MMSE points per year. While that change is relatively small over a single year, the researchers say it could become more meaningful if it continues over a longer period.

"The difference is modest for an individual patient from one year to the next, but over a longer period even such an effect could influence how cognitive function develops. Our findings suggest that NOAC treatment may also be significant for cognition in this patient group," says Nanbo Zhu, researcher at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet.

Lower Risks of Stroke and Other Complications

The potential benefits were not limited to cognition. Compared with people who did not receive anticoagulants, those treated with NOACs also had lower risks of death, stroke, blood clots and fractures.

Warfarin was also associated with lower risks of death, stroke, and blood clots. However, people taking warfarin had a higher risk of major bleeding.

Why the Findings Need Caution

The researchers emphasize that the study has important limitations. Because it was observational, the results cannot prove that NOACs directly caused the slower cognitive decline or the other health benefits seen in the data.

Some factors that could affect both which treatment a patient received and how their health changed over time could not be fully evaluated. The researchers also note that some participants may have switched from one medication to another during the follow-up period.

The study was funded by, amongst others, the Swedish Research Council, the Swedish Brain Foundation, CIMED, ALF project funding and Karolinska Institutet funds. Maria Eriksdotter has participated as a consultant in one-off meetings with BioArctic AB, Roche, Eli Lilly, Biogen/Eisai and Novo Nordisk, and has given lectures at symposia sponsored by Roche and BioArctic/Eisai. No other conflicts of interest are reported.