Adults with even mild forms of sickle cell disease scored lower on tests of brain function than their healthy cohorts, suggesting that the disorder has a bigger impact on the brain than had previously been recognized, researchers reported Tuesday. The effects were found to become more severe with increasing age and more severe presentations of the disorder. A recent report showed that children with the disorder can suffer mental impairment, but the new study reported in the Journal of the American Medical Assn. is the first to look at brain function in adults.
Sickle cell disease, which affects about one in every 350 African American children, is a genetic disorder that causes red blood cells to assume a sickle shape under stress, clogging blood vessels and producing episodes of excruciating pain, called crises. The clogged vessels can damage all internal organs and can be lethal if not treated. At least a quarter of victims suffer strokes. Most victims used to die in childhood or adolescence, but improvements in therapy have increased lifespans past the age of 50.
The primary treatment is the drug hydroxyurea, which reduces crises by 50% and mortality by 40%. The disease can be cured by bone marrow transplants, but those entail risks of their own and most patients do not have suitable donors. It is also treated with blood transfusions.
In the new study funded by the National Heart, Lung and Blood Institute, Dr. Elliott Vichinsky of Children's Hospital & Research Center in Oakland and his colleagues studied 149 adult sickle cell patients for whom imaging showed no significant impact on the brain and compared them with 47 healthy people from the same community. The patients were all considered to have a mild form of the disease because they had not suffered frequent pain, hospitalization, stroke, hypertension or other characteristic problems.
The subjects were given a variety of tests of mental functioning. On average, the sickle cell patients were in the normal range, but a third of them scored significantly below normal levels, compared with only 15% of the healthy controls. Those with the lowest scores were older and had the lowest levels of hemoglobin, the oxygen-carrying component of red blood cells.
"This study suggests that some adult patients who have sickle cell disease may develop cognitive problems, such as having difficulty organizing their thoughts, making decisions or learning, even if they do not have severe complications such as stroke," Dr. Susan B. Shurin, acting director of the NHLBI, said in a statement. "Such challenges can tremendously affect a patient's quality of life, and we need to address these concerns as part of an overall approach to effectively managing sickle cell disease."
Vichinsky is now testing new therapies for the disorder, such as blood transfusions every two to three months, to determine whether they can reduce the disorder's effect on the brain.
-- Thomas H. Maugh II
Blood transfusions are one treatment for sickle cell disease, which has been found to impair mental functioning in adults. Credit: Baltimore Sun / Jed Kirschbaum