Study Finds Poorer Cognitive Performance Among Adults With Sickle Cell Anemia
Compared with a group of healthy study participants, adults with sickle cell anemia showed poorer performance on neurocognitive tests, which was associated with anemia and age, according to a study in the May 12 issue of JAMA.
While the average life span for patients with sickle cell anemia (SCA) now exceeds 50 years, SCA has become a chronic illness associated with progressive deterioration in quality of life, according to background information in the article. “Neurocognitive dysfunction may be the most important and least studÃ‚ied problem affecting this aging popuÃ‚lation,” the authors write. “To our knowledge, conÃ‚trolled studies of neurocognitive funcÃ‚tion in adult patients have not been reported, and routine screening after childhood is not performed.”
Elliott P. Vichinsky, M.D., of Children’s HosÃ‚pital & Research Center Oakland, Calif., and colleagues conducted a study to measure neurocognitive dysfunction in neurologically asymptomatic adults with SCA vs. healthy control individuals. The study included a comparison of neuropsyÃ‚chological function and neuroimaging findings between adults with SCA and controls from 12 SCA centers, conducted between December 2004 and May 2008. Participants were patients with SCA, ages 19 to 55 years, and of African descent (n = 149) or comÃ‚munity controls (n = 47). Participants were stratified on age, sex, and education.
The primary outcome measured was nonverbal function, as assessed by the Wechsler Adult Intelligence Scale, third edition (WAIS-III) PerÃ‚formance IQ Index.
The researchers found that after adjusting for age, sex, and eduÃ‚cation level, the SCA patients had statistically significant lower average nonverbal funcÃ‚tion scores than controls. The WAIS-III PIQ score was more than 1 standard deviation below the normaÃ‚tive average for 33 percent of patients and 15 percent of controls, compared with an exÃ‚pected 16 percent from the national norms. The authors suggest that patients with scores in the below-average range may have challenges in skills of daily life such as employment, financial management, medication adherence, use of community resources and soÃ‚cial functioning.
SCA patients also had lower average scores for measures of proÃ‚cessing speed, working memory, global cogniÃ‚tive function, and the maÃ‚jority of measures of executive function. Difficulties with selective attention in SCA patients were illustrated by lower average scores for tests regarding visual scanning and atÃ‚tention.
MRI findings did not exÃ‚plain the performance differences in the subset of patients with neuroimaging studies, as no differÃ‚ences in total gray matter or hippocampal volume were observed. Anemia was associated with poorer neurocognitive function in older patients.
“Adult patients with SCA who are neuÃ‚rologically asymptomatic are still at risk for neurocognitive performance defiÃ‚cits, because their anemia may be inÃ‚ducing neurocognitive impairment secondary to cerebral hypoxemia [deficient oxygen in the blood] unÃ‚detectable by standard neuroimaging studies. Several practical steps can be taken. First, early identification of paÃ‚tients with difficulties on specific measures of neurocognitive function may allow these patients to enroll in and benefit from cognitive rehabilitation programs. Additionally, longitudiÃ‚nal studies are necessary to underÃ‚stand and evaluate disease progression. These studies can be linked to biological components to improve unÃ‚derstanding of neurocognitive funcÃ‚tion in SCA,” the authors write.
“Overall, the results of this study sugÃ‚gest that neurocognitive performance is not adequately explained by findÃ‚ings on standard neuroimaging studÃ‚ies and support the need for intervention studies evaluating transfusion therapy, neuroprotective agents, hydroxyurea [a sickle cell anemia treatment], and oxygenation to deterÃ‚mine whether such treatments will improve cognition.”
Editorial: Neurocognitive Complications of Sickle Cell Anemia in Adults
In an accompanying editorial, Samir K. Ballas, M.D., of Thomas JefÃ‚ferson University, Philadelphia, comments on the findings of this study.
“Neurocognitive deficits may be overlooked in adult paÃ‚tients with SCA or discounted as a manifestation of malÃ‚adaptive behavior rather than recognized as the result of an organic process. This study suggests that standardized and comprehensive neuropsychological assessment may be a valuable tool in the management of adult patients with sickle cell disease [SCD].”
“Like neurocognitive deficits, chronic sickle cell pain does not fit into either pathogenetic pathway and is difficult to diagnose. During the transition from acute to chronic pain, significant changes occur within the central nervous sysÃ‚tem, indicating that chronic pain evolves into a neurologic disorder. Neurocognitive deficits and chronic pain are both neurologic disorders of SCD, and both do not maniÃ‚fest with objective signs.”
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