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What Causes Dementia? Anemia Is Part of the Puzzle

B0007649 Blood cells in a blood vessel
Wellcome Images

In yet another study linking healthy blood flow to brain health, new research finds that older adults with anemia - low levels of red blood cells - have an increased risk for dementia.

Previous research has linked uncontrolled high cholesterol and high blood pressure to increased risk of dementia. Now this large new study finds that anemia also increases dementia risk.

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Researchers tested 2,500 older dementia-free adults in Memphis, Tenn., and Pittsburgh, Pa., for anemia, memory and thinking skills. They then tested them for dementia 11 years later. They published results yesterday in the journal Neurology.

"People with anemia had a 60 percent increased risk of developing dementia," says lead author Kristine Yaffe, M.D., with the University of California, San Francisco. Even after researchers adjusted their statistics to account for other factors that might influence results, such as age, sex and education levels, they found those who had anemia at the start of the study had more than 40 percent higher risk of developing dementia than those who were not anemic.

A few previous studies have linked anemia to a higher risk of dementia, but researchers weren't sure whether the anemia was linked to dementia or that the condition causing the anemia - such as poor health or poor eating habits - was the culprit. Anemia is common in older people and occurs in up to 23 percent of adults ages 65 and older.

"This is the most convincing study linking anemia and dementia," Yaffe says. Because the study followed a large group of diverse older adults for more than a decade, these researchers are fairly certain that not having enough red blood cells is somehow linked to the disease. But why?

Yaffe suspects the link is related to lower oxygen levels to the brain caused by anemia. Red blood cells carry oxygen from our lungs to the rest of our body, including our brains, which need plenty of healthy blood to function properly. When we don't get enough of that oxygen-rich blood, this seems to compromise our brain health.

The important question, of course, is whether treating or preventing anemia will help protect the brain. Yaffe says scientists are working on answering that question, but until then she recommends that older adults ask their doctors to check for anemia and follow recommendations to treat it. Yaffe and other doctors caution against simply adding an iron supplement to your diet. There are 400 different types of anemia - caused by a vitamin B-12 deficiency, kidney disease and other conditions - and too much iron can be harmful to older people.

"We're concerned that when physicians see anemia in older patients they have a tendency to prescribe iron, or folate, or vitamin B-12, believing that it's safe. Actually, that may not be the case, particularly for iron," says Ashley Bush, M.D., director of the Oxidation Biology Laboratory at the Florey Institute of Neuroscience and Mental Health in Melbourne, Australia. He recommends that doctors discover the cause of the anemia - whether it's a nutritional deficiency or another problem - before deciding on a treatment.


Photo Credit: Wellcome Images


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