Anemia Linked with Higher Dementia Risk

August 1, 2013

News Review From Harvard Medical School -- Anemia Linked with Higher Dementia Risk

Older adults with anemia may be more likely to develop dementia. That's the finding of  a new study. Researchers looked at blood samples for more than 2,500 men and women in their 70s. About 400 had anemia. This means they had lower than normal levels of red blood cells. The study lasted 11 years. In that time, about 23% of those with anemia developed dementia. So did 17% of those without anemia. Researchers also adjusted their numbers to account for differences in age, race, sex, education and other factors between the 2 groups. They found that people with anemia were 41% more likely to develop dementia than those without anemia.  The study does not prove that anemia causes dementia. Some other condition or lifestyle factor could increase the risk of both. The journal Neurology published the study online. HealthDay News wrote about it July 31.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Dementia is common among the elderly.  But it doesn't always happen.   

Consider the example of my grandmothers.  My mother's mother reached age 90 while continuing to work, living alone and taking care of herself.  We all described her as "sharp as a tack."  Meanwhile, my father’s mother had advanced dementia well before her 75^th birthday. 

Both lived long lives.  But why did their brain function differ so much?

Genes clearly affect the development of dementia.  Researchers have linked some genes with dementia.  And we know that dementia can run in families.  But even when it does, not everyone who is part of an affected family or carries a suspect gene becomes demented.   Many people with dementia have no family history of the disease.  Often, the development of dementia seems random, a matter of chance or bad luck.

Yet it's probably not random.  Much more likely is that we simply don't know enough to determine why some people develop dementia while others do not. In fact, this is a major focus of research.

A possible clue comes with news that anemia -- an abnormally low red blood cell count -- may increase the risk of dementia.  The journal Neurology published the study. It included more than 2,500 people between the ages of 70 and 79. During the following 11 years:

• About 18% developed dementia
• About 23% of those with anemia and 17% of those without anemia developed dementia

Researchers then accounted for differences between the two groups, such as age, race and gender. They found that the risk of dementia was 41% higher in the group with anemia.

It's hard to know how important these findings are.  It's possible that anemia actually causes dementia.  Red blood cells carry oxygen throughout the body.  A low red blood cell count might mean less oxygen will get to the brain. Perhaps that might lead to dementia. In that case, finding the cause of anemia and correcting it might prevent dementia.

But it's also possible that the anemia is an indication of other diseases (such as high blood pressure or diabetes) that may affect both blood counts and brain function.

What Changes Can I Make Now?

For most people, anemia is not a disease.  It's an effect of another disease or condition. These include:

• Loss of iron (caused by  menstrual bleeding, a bleeding ulcer or other causes)
• Poor kidney function
• A long-term (chronic) disease, such as rheumatoid arthritis

Many people think they can cure their anemia by taking iron pills or increasing their intake of iron (as in red meat).  But that only works if you don't have enough iron in your body.   And that approach may overlook an important cause of bleeding, such as a colon polyp or even colon cancer.  So, if you are anemic, talk to your doctor about the causes and treatments.

You also can make changes to reduce your chances of dementia in the future.  Here's what you can do:

• Exercise regularly.
• Maintain a healthy weight.
• Choose a diet that's high in fiber, fruits, vegetables and omega-3 fatty acids.
• Keep your blood pressure and blood lipids (such as cholesterol) in a healthy range.
• Don't smoke.
• Keep your mind active. For example, have a busy social life and hobbies, and engage in activities that challenge your mind.

It's important to recognize that symptoms that suggest dementia (such as poor memory) may have some other cause. Sometimes depression, thyroid disease or other treatable conditions may mimic dementia.  If you are concerned that you or a loved one may be developing dementia, it is important to have a thorough medical evaluation.

What Can I Expect Looking to the Future?

The findings of this new research raise several questions.  These include:

• Does the type of anemia matter and what is the role of related conditions?  It’s possible that some types of anemia increase the risk of dementia more than others.
• Does the severity of anemia matter?  We could learn that mild anemia does not have much effect on the risk of dementia but more significant anemia does.
• Does it matter how long anemia has been present? This new research did not determine how long people had anemia before they developed dementia.

You can expect future research to confirm (or refute) the idea that anemia increases the risk of dementia and to address these important questions.