Dementia risk and AFib: Some blood thinners may help lower risk

  • The use of direct oral anticoagulants, or ‘DOACs,’ is associated with a significantly lower incidence of dementia in a new study, compared to the use of traditional blood thinner warfarin.
  • The study is primarily concerned with people living in Asia, and the lower incidence of dementia did not apply to other populations.
  • Blood thinners prescribed for cardiovascular conditions such as atrial fibrillation may prevent dementia that results from years of mini-blood clots in the brain.

The use of direct oral anticoagulants (DOACs), a form of direct blood thinners, instead of the traditional blood thinner warfarin, was associated with a significantly lower risk of dementia in Asian people receiving treatment for atrial fibrillation (AFib), according to a new study, which appears in JACC: Asia.

The risk of dementia in those treated with DOACs was 12% lower than in those treated with warfarin.

Blood thinners, or anticoagulants, thin the blood to help prevent blood clots and break down any existing clots.

While blood clotting is vital to healing external injuries, when clots form in the bloodstream, they may break loose and cause life-threatening blockages in the brain, heart, or lungs.

Physicians prescribe anticoagulants to prevent strokes, pulmonary embolisms, and heart attacks. They are also indicated for AFib in order to prevent such cardiovascular events.

The current research was a meta-analysis of 10 previous studies, one of which was conducted in the United States. The studies totalled 342,624 participants between them, and nine out of the 10 studies indicated that DOACs were associated with lower rates of dementia.

When the researchers factored in different geographic locations, the greater benefit of DOACs applied only to Asian populations.

The study also found that while DOACs were linked to less dementia in people younger than 75 years, there was no such association for people older than that.

Blood clots and dementia

There are numerous forms of dementia, including Alzheimer’s disease and vascular dementia.

Dr. Cheng-Han Chen, an interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, not involved in the current research, characterized vascular dementia as “lots of small blood vessels that get blocked over time.“

“You could even call them micro-blockages that we normally wouldn’t even know about until 20 years later when [a person has] dementia. It’s coming from the brain having all this small damage over the long term,” he explained.

Anticoagulants may help prevent vascular dementia, Dr. Chen noted, saying that “[i]t’s possible that if someone’s on blood thinners for atrial fibrillation to protect them from ischemic stroke from AFib, and the blood thinner is also helping prevent a lot of the really small stuff.”

Why DOACs won over warfarin

Given the delicate balancing act between thinning a person’s blood for preventive reasons without impacting their ability to form clots for external wounds, one of the risks of anticoagulants is excessive bleeding.

“Warfarin used to be the only option we had. It’s a very old drug. It’s a blood thinner that is kind of, let’s just say, annoying to use,” said Dr. Chen, referring to the dietary restrictions and regular blood tests that accompany its use.

To help warfarin work, explained Dr. Chen, “You have to watch your diet very carefully, and what you can eat, and also you have to measure your blood every once in a while to measure how thin your blood is, and then adjust your dose based on that.”

People on warfarin are not allowed foods that contain vitamin K, which helps blood clots form for healing. These foods include green leafy vegetables. Vitamin K is actually the opposite of warfarin, undoing its blood-thinning.

Dr. Chen hypothesized that the inability to eat such an important category of food may have influenced the reduced health of people in the study who took warfarin.

However, he continued, “[a]bout 10, 20 years ago, the drug companies invented this new class called ‘DOACs.’ And those you just [take them], and you don’t have to measure your blood or have to watch your diet. So you can imagine that those kind of took over.”

DOAC not without downsides

Still, DOACs are not without their own problems. Dr. Chen raised the lack of a readily accessible antidote to DOACs as a significant problem. He said ”they’re super-expensive and they’re not very common.”

Cost is also an issue with DOACs. “The drug companies charge a lot more, and even if the insurance covers it, there’s usually a high copay for a lot of insurance plans. So, you know, if they were the same price, I think almost everybody would be on DOACs instead of warfarin nowadays.”

Nonetheless, cardiologist Dr. Jayne Morgan — executive director of Health and Community Education AT Piedmont Healthcare, and adjunct associate professor of medicine at The Morehouse School of Medicine in Atlanta, GA, also not involved in the study — raised some serious issues regarding DOACs.

She said:

“There are considerations with prosthetic heart valves, as well as some types of antiphospholipid syndromes — especially if triple-positive for the lupus anticoagulant, anticardiolipin antibodies, and anti-beta 2 glycoprotein 1 antibodies — as DOACs could be associated with increased thrombosis as compared with warfarin, a vitamin K antagonist.”

Dr. Morgan noted, even so, that the current trend in prosthetic heart valves is leaning toward an increasing use of DOACs instead of warfarin in patients with AFib. She said that current data suggests similar mortality rates.

Do the findings apply to different populations?

The authors of the study hypothesized that Asians’ relatively smaller body sizes might allow anticoagulants to achieve a stronger effect at standard doses that helped reduce the development of dementia.

“This particular paper,” said Dr. Morgan, “compiled studies that included data subjects specific to Korea and Taiwan. It is therefore unclear whether this can be extrapolated to all Asians.”

It may also not apply to Asians living in the United States, said Dr. Chen. “Asian populations are not necessarily the same thing as Asian-American populations,” he emphasized.

“If you’re an Asian person,” said Dr. Chen, speaking as a cardiologist, “but you grow up eating an American diet, your heart disease risk is going to be much more close to an American white person than your Asian grandfather living in Asia, or your Asian cousins still living in Asia.”

“If you’re talking about a person who just moved here from Asia, then that study would be applicable to them,” said Dr. Chen.

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