SALT LAKE CITY — A new study shows that dementia rates increase when blood thinner treatment is put off for people with atrial fibrillation, the most common heart arrhythmia.

The first-of-its-kind study at the Intermountain Medical Center Heart Institute included more than 76,000 patients with no prior history of dementia who were treated with an antiplatelet or warfarin, a medication used to treat or prevent blood clots in veins or arteries.

Heart arrhythmia affects more than 2.7 million Americans.

"Our results reinforce the importance of starting anticoagulation treatment as early as possible after a patient is diagnosed with atrial fibrillation," said Dr. Jared Bunch, Intermountain director of heart rhythm research.

Bunch said one of the challenges with blood thinners is that they're often used late and inappropriately.

Researchers saw for the first time that waiting even 30 days to start anticoagulation treatment can increase a person’s long-term risk of developing dementia, he said.

The study results were presented Friday at Heart Rhythm 2017, the Heart Rhythm Society’s 38th annual Scientific Sessions in Chicago.

"We’d hope, moving forward, physicians would recognize that aspirin really is not an effective drug alone to prevent stroke and that they would start warfarin immediately and not wait," Bunch said.

Researchers studied patients from the time they were diagnosed with atrial fibrillation to when they were placed on blood thinners.

Patients were divided into two categories: those who received immediate treatment (started less than 30 days from diagnosis) and those who received delayed treatment (started after one year).

Using a measurement scale known as the CHADS2 Vasc score to predict stroke risks and identify those at highest risk of cognitive decline with a delay in therapy, researchers found the risk of dementia in low-risk patients was 30 percent higher for those who received delayed treatment, and a significant 136 percent higher for high-risk patients.

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“We want to ensure we’re doing everything possible to limit the risk of brain injury for our patients, and our study not only shows the importance of early therapy, but also shows the very limited role, if any, of aspirin for stroke prevention,” Bunch said.

Anticoagulants, or blood thinners, like antiplatelets and warfarin are powerful stroke prevention therapies and are prescribed to millions worldwide.

"Even if people aren't started on it immediately, there is benefit in starting it as soon as people hear the results of this study as far as protecting the brain down the road," Bunch said.

However, there’s often a delay in starting blood thinners after an initial diagnosis of atrial fibrillation for a variety of reasons, including low risk of stroke, exploration of other treatment options like aspirin, and older age.

"In this study, the benefit was derived from using warfarin, and we hope newer anticoagulants that perform better than warfarin and are easier to start and use will further improve dementia risk," Bunch said.

The authors of the study call for additional studies to increase understanding of how the risk of dementia increases over a longer period of time.

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