Reading ability as an estimator of premorbid intelligence: Does it remain stable in emergent dementia?

The 6-year stability of reading performance was investigated in subjects who were normal at baseline but suspect for dementia at follow-up (MMSE score less than or equal to 23; n = 197). and in a cognitively intact control group (n = 117). The Dutch version of the National Adult Reading Test (DART) was used. The DART-based estimate of IQ appeared to be very stable in healthy elderly. In the "suspect" group, the decline after 6 years was about 3 IQ-points in subjects who were still nor demented, minimally demented, or mildly demented. Reliability remained satisfactory in these subgroups. In cases with moderate and severe dementia, the decline was considerable (greater than or equal to 15 IQ points). The decline of DART IQ was related to deterioration of semantic memory as reflected in verbal abstraction and category fluency. It is concluded that the DART remains a valid estimator of premorbid verbal intelligence in mild and questionable dementia. A formula is presented which can correct the underestimation on the basis of the MMSE store.