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Sickle-cell anemia can lead to lower IQ scores, study shows

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sickle cell anemia cognitive function iqSymptoms of sickle-cell anemia often include severe pain and other major medical complications, but a new study shows that the disease might also decrease cognitive abilities in young and middle-aged adults.

About 70,000 people in the U.S. have sickle-cell anemia (SCA), but improved therapies are allowing most people with it to live well beyond the age of 50.

The disease causes the hemoglobin protein in oxygen-carrying red blood cells to be misshapen. This in turn makes the blood cells stiffer and more concave, shaped like a sickle rather than a round disc. These firmer, C-shaped cells are prone to jam together and block blood flow. The disease occurs most widely in people of African descent, and "its clinical presentation involves a multitude of complications involving all organs," Samir Ballas, of the Cardeza Foundation for Hematologic Research at Thomas Jefferson University’s Jefferson Medical College, wrote in an editorial accompanying the new study, published online May 11 in JAMA, the Journal of the American Medical Association.

But "brain dysfunction may be the most important and least studied problem affecting individuals with this disease," the authors of the new study noted in their abstract. Anemia in general has been associated with poor brain oxygenation and perfusion, but a controlled study of cognitive function in adults with SCA had not yet been done.

To test the disease’s relation to cognitive decline, 20 researchers, led by Elliott Vichinsky, of the Department of Hematology and Oncology at the Children’s Hospital & Research Center Oakland, submitted 149 adults ages 19 to 55 with SCA (and no history of brain injury, stroke, major organ dysfunction or other chronic conditions that might impact cognitive fitness) and 49 healthy African-American controls to an IQ test and other tasks to assess overall cognitive capabilities. Vichinsky and his team found those with SCA had "significantly lower" IQ scores than the healthy subjects (86.69 compared with 95.19 for the controls). Tests of memory, attention, language and executive function also revealed that the SCA group was lacking in mental capabilities relative to controls.

"Neurocognitive deficits may be overlooked in adult patients with SCA or discounted as a manifestation of maladaptive behavior rather than recognized as the result of an organic process," Ballas noted in his editorial.

To ascertain any changes in the brain itself, the researchers performed MRI (magnetic resonance imaging) of some SCA patients and healthy subjects. They found no difference in the size of the hippocampus or gray matter. But with age, total brain volume did appear to decrease along with cognitive ability in the SCA patients. Lower hemoglobin levels—as well as lower education levels—were also associated with poorer cognitive performance in the patient group.

The researchers did not test patients with other forms of anemia to determine whether this cognitive decline was specifically tied to sickle-cell disease or would likely be manifest in other types as well. Ballas also noted that the SCA patients in Vichinsky’s study were relatively healthy and more homogenous than the overall SCA patient population.

Vichinsky and the other authors are now working on a pilot study to see if a blood transfusion would help boost cognitive function among those with SCA who scored below 90 on the IQ test.

Image of sickle cells courtesy of Wikimedia Commons/NIH

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  1. 1. JamesDavis 8:53 am 05/12/2010

    I can see all the Republicans jumping on this banwagon. Now, they’ll say President Obama has Sickle Cells for brains.

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  2. 2. Dr.MeliD 11:34 am 05/12/2010

    They had my attention up to, "Lower hemoglobin levelsas well as lower education levelswere also associated with poorer cognitive performance in the patient group."… Oh, so… what you’re saying is the group that tested for a lower IQ also had a significantly lower level of education. Uh huh. But what we should really take home is that SCD decreased their IQ. …smh… NEXT!

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  3. 3. jtdwyer 3:49 pm 05/12/2010

    I don’t know about sickle cell anemia, but I happen to have a weakened heart and last year completed 11 mo. of chemo. producing severe anemia. I can tell you that reducing the level of oxygen and nutrients supplied to brain cells produces a wide variety of detrimental effects. I didn’t take any IQ tests during that period, but I spent a lot of time trying to figure out why I had gone to the kitchen and what I’d intended to do there… I was much better a few weeks after the chemo.

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  4. 4. Wayne Williamson 6:07 pm 05/12/2010

    Dr.MeliD…thanks for point that out…missed it on the first pass…they should have also used education levels on the control group when rating IQ….

    jtdwyer…i agree with the article and you…impaired oxygen & nutrients would impact brain function…hope your doing ok…

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  5. 5. rhodinsthinker 7:19 pm 05/12/2010

    I had seen somewhere, I believe in the Scientific American, that the same gene that causes susceptibility to sickle cell anemia also confers resistance to malaria.

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  6. 6. jtdwyer 10:44 pm 05/12/2010

    rhodinsthinker – I’ve heard that, too. Mosquitoes must be picky eaters… Would you eat those sickle-cells?

    Wayne Williamson – Much better, thanks. I’m spending less time staring at the refrigerator and more time eating stuff.

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  7. 7. supaumar 11:46 am 05/15/2010

    @ rhodinsthinker & jtdwyer

    Malaria cannot reproduce in sickled cells. This is why SCA is so prevalent in Africans. Africa obviously has/had a large occurrence of malaria. Those heterozygous for SCA survived not only malaria, but felt little effects of SCA.

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  8. 8. jtdwyer 2:09 pm 05/15/2010

    supaumar – Excellent point of SCA’a benefit in avoiding malaria, but I don’t understand how there’d be little effect from SCA.

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  9. 9. blue7053 9:14 pm 05/15/2010

    This African response to Malaria has been known for a hundred years but it’s never mentioned because it affects Blacks, African-Americans, Negroes?

    There is no greater prejudice than rejecting truth in favor of Political Correctness.

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  10. 10. supaumar 11:48 pm 05/15/2010


    Those that are heterozygous for SCA ("carriers") rarely exhibit symptoms of SCA. This is because the sickled cells essentially stop the pathogen until the immune system can destroy it. Since malaria was prevalent, evolution has resulted in a large amount of Africans heterozygous for the trait. And since heterozygotes have a 50% chance of having a heterozygote and a 25% chance of having a child with full blown SCA, it remains prevalent. If there were no evolutionary benefit in being heterozygous for SCA, it would have died out a long time ago and would be nowhere near as prevalent.


    I absolutely agree with you.

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  11. 11. jtdwyer 2:59 am 05/16/2010

    supaumar – Thanks for explaining. Unless I’m misunderstanding though, you explained how the malaria symptoms are avoided, improving the survivability of those with Sickle Cell Anemia.

    However, they should still suffer the affects of anemia, correct? As I understand, they result from the reduced ability of sickled red blood cells to transport oxygen, nutrients and cellular waste product throughout the body for processing.

    So, while SCA can prevent malaria infection, it has its own symptoms produced by the cellular effects, correct? Thanks for your patience.

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