A principle objective of the National Institute of Health’s Strategic Plan and Budget to Reduce Health Disparities is “developing new and improved approaches for detecting, diagnosing, preventing, treating or delaying onset or progression of diseases and disabilities that contribute to health disparities (U.S. DHHS, 2002
).” For clinicians and cognitive scientists, it is essential that appropriate normative test data be available to screen for cognitive impairment and to better understand disease process versus bias artifact in conducting research with diverse and representative U.S. populations (Lampley-Dallas, 2001
The Symbol Digit Modalities Test (SDMT) is a widely used, brief screening test for neurologic disorders (Smith, 1968
). The cognitive demands of the SDMT include attention, visual scanning, and motor and psychomotor speed. The SDMT is purportedly sensitive to a wide-range of neurologic and neuropsychiatric disorders, but may lack disorder specificity (Lezak, Howieson, & Loring, 2004
). Impaired SDMT performance has been reported in otherwise healthy adults with white matter hyperintensities, and a variety of pathologic conditions, such as traumatic brain injury, and subtypes of multiple sclerosis (Felmingham, Baguley, & Green, 2004; Huijbregts et al., 2004; Sachdev, Wen, Christensen, & Jorm, 2005). Thus, the SDMT is a useful screening test provided that it is appropriately calibrated to the population of intended use.
A recent review of published SDMT normative data indicates that it is widely used; however, normative data is lacking for adult racial/ethnic minority groups (Sheridan et al., 2005
). In recent years, more normative data for African Americans have become available for neuropsychological tests (e.g., (Byrd, Touradji, Tang, & Manly, 2004
; Moering, Schinka, Mortimer, & Graves, 2004). Most studies have focused on adults over age 60, which may be of limited utility to clinicians and investigators working with a wider range of adults (Fillenbaum, Heyman, Huber, Ganguli, & Unverzagt, 2001; Friedman, Schinka, Mortimer, & Graves, 2002; Lucas et al., 2005; Manly, Byrd, Touradji, & Stern, 2004
; Mast, Fitzgerald, Steinberg, MacNeill, & Lichtenberg, 2001). Additionally, ethnicity among Blacks and test performance has rarely been examined (Byrd, Sanchez, & Manly, 2005
). Currently, normative data is unavailable for younger Caribbean Blacks who, some argue, may be culturally and socioeconomically distinct from other Blacks (Williams & Jackson, 2000
). The purposes of this study were to determine significant correlates of a modified version of the SDMT performance and provide normative data for clinical and research use from a large, nationally representative sample of African Americans, Blacks of Caribbean ancestry, and non-Latino Whites (NLW) living in areas with large populations of Blacks.