The African American elderly population in the US is projected to increase by 131% by year 2030 [1
]. There is growing interest in estimating who and how many within this population will be affected by cognitive impairment. The etiology of cognitive impairment has not been well studied in African Americans due, in part, to their lack of willingness to participate in research studies as well as the lack of ascertainment efforts to have them represented [2
]. Previous research on European Americans suggests that there is a strong genetic influence on Alzheimer’s Disease (AD) [3
]. AD and other types of dementia are usually preceded by cognitive impairment. Therefore, the assessment of cognitive impairment is central to timely dementia diagnosis.
Several popular measures designed to assess cognitive impairment in dementia, including the Orientation-Memory-Concentration test [5
], Storandt Battery [6
], Iowa Battery [7
], Mini-Mental State Examination (MMSE) [8
], and the Kahn-Goldfarb Mental Status Questionnaire [9
], have been found to have higher false positive rates in comparison to more in depth clinical diagnostic criteria such as the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer’s Disease and Related Disorders Association (NINCDS-ADRDA) guidelines [10
]. One of the major sources of inaccuracy stemmed from not taking race and educational levels into account [10
]. There has been an effort to establish revised cutoffs to make more accurate assessments using established cognitive screeners. For example, Kiddoe et al. [11
] compared prevalence of cognitive impairment in a sample of African American twin pairs when using the Telephone Interview of Cognitive Status (TICS; 12) as opposed to the Short Portable Mental Status Questionnaire (SPMSQ; 13), which has been found to be less biased toward African Americans than other cognitive tests [14
], and found that reducing the cutoff from 30 to 27 may improve the specificity of the instrument in this population. The TICS has been used in a prior study to estimate concordance rates in community dwelling female twin pairs [15
]. However, results showed very low incidence rates of cognitive impairment in this group and in addition, none of the pairs were found to have both twins affected.
In the present study, we examine the genetic and environmental proportions of variability in cognitive impairment by examining the concordance rates and heritability among older African American twins.