To the Editor.
—We would like to comment on the interesting article of Filley et al1 concerning the neuropsychological features of early and lateonset Alzheimer's disease (AD).The authors interpreted their findings to mean that patients with onset of AD before age 65 years have more language impairment, and that those with onset at later ages have more impairment in visuoconstructive performance. We believe that these conclusions are not warranted. First, there is overrepresentation of verbal scores in their study; only three of 12 scores presented in their Table are measures of visuospatial performance. Also, of the seven language scores used, significant differences were found for only two tests. If Bonferroni corrections for multiple comparisons are applied, only one language score would yield significance. Furthermore, the visuospatial scores presented as "spatial relations" are a nonindependent composite of two subtests presented elsewhere in the Table. Thus, we believe that performance
Koss E, Friedland RP. Neuropsychological Features of Early and Late-Onset Alzheimer's Disease. Arch Neurol. 1987;44(8):797. doi:10.1001/archneur.1987.00520200005005
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