Differentiating illiteracy from Alzheimer's disease by using neuropsychological assessments

In Asia, where illiteracy rates are high, determining the degree to which neuropsychological measures can be used to identify cognitive impairment in illiterate elders is important. The aim of this study was to evaluate the effectiveness of using formal neuropsychological assessments to distinguish healthy illiterate elders from dementia patients.

We compared the cognitive performance of healthy elders who were illiterate (illiterate NC, n = 25) with those who were literate (literate NC, n = 25), literate patients with mild Alzheimer's disease (literate AD, n = 25), and illiterate patients with mild AD (illiterate AD, n = 25). Neuropsychological measures included the Mini-Mental State Examination (MMSE), the verbal fluency test, the Boston naming test, the Rosen drawing test, and the verbal learning test.

In the between-group analyses, the scores on all tests, except verbal fluency and recognition memory, were lower for illiterate NC compared to the literate NC. The scores on the MMSE, Boston naming test, Rosen drawing test, and immediate free recall could not distinguish the illiterate NC from literate AD. However, the scores on all tests, except the Rosen drawing test, could distinguish illiterate NC from illiterate AD. ROC analyses showed the same pattern of results. In addition, age-, sex-, and education-matched cut-off scores of all tests, except immediate recall and delayed recall trials of the verbal learning test, showed good specificities in participants who were illiterate compared to those in participants who were literate.

These findings suggest that the impact of literacy on neuropsychological test performance is an important aspect of cognitive evaluations for elders who are illiterate.