Atrial fibrillation is a common heart rhythm condition in older adults and affects many people living with Alzheimer’s disease. Doctors often prescribe anticoagulants, or blood thinners, to reduce the risk of blood clots and stroke.

Previous research has suggested that anticoagulant treatment may lower the risk of developing dementia. However, less is known about whether these medications affect cognitive decline after Alzheimer’s disease has already been diagnosed.

“There is reason to believe that this treatment may have positive effects on cognition, such as improving blood flow and reducing small-scale brain damage,” says Maria Eriksdotter, professor at the Department of Neurobiology, Care Sciences and Sociology at Karolinska Institutet and senior consultant in geriatric medicine at Karolinska University Hospital, who led the study.

Study compared NOACs, warfarin and no anticoagulant treatment

Researchers analyzed data from SveDem, the Swedish Cognitive Impairment/Dementia Registry. The study included 7,308 people diagnosed with both atrial fibrillation and Alzheimer’s disease.

Participants were divided into three groups:

• People treated with a newer anticoagulant known as a NOAC
• People treated with the older blood thinner warfarin, also known as Waran
• People who did not receive anticoagulant treatment

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

NOAC treatment was associated with slower cognitive decline

People taking NOACs experienced a significantly slower decline in cognitive function than those treated with warfarin or those who did not receive anticoagulants.

The difference was slightly more than 0.2 MMSE points per year. Although the difference was relatively small over a single year, the researchers said it could become more meaningful over a longer period.

“For individual patients, year-to-year differences are small, but over the long term, even such effects can influence cognitive development. Our results suggest that NOAC treatment may also be important for cognition in this patient group,” says Nanbo Zhu, a researcher at Karolinska Institutet’s Department of Neurobiology, Care Sciences and Society.

NOACs were also linked to lower risks of stroke and death

The potential benefits associated with NOAC treatment were not limited to cognitive function. Compared with people who did not receive anticoagulants, people treated with NOACs also had lower risks of death, stroke, blood clots and bone 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.

Study limitations mean the results do not prove cause and effect

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

The researchers could not fully assess all the factors that may influence which treatment a patient receives or how the patient’s health changes over time. They also noted that some participants may have switched from one anticoagulant to another during the follow-up period.

The research was funded by the Swedish Research Council, the Swedish Brain Foundation, CIMED, ALF project funds, Karolinska Institutet funds and other organizations.

Maria Eriksdotter has participated as a consultant in one-off meetings with BioArctic AB, Roche, Eli Lilly, Biogen/Eisai and Novo Nordisk, and has presented at symposiums sponsored by Roche and BioArctic/Eisai. No other conflicts of interest were reported.