Age at onset and visuocognitive disturbances in Alzheimer disease.

We examined the relation of age at onset and visuocognitive disturbances in Alzheimer disease (AD) using a large sample of patients, quantitative neuropsychological measures, and multivariate statistics controlling for gender, education, stage of dementia, and disease duration. Significant positive coefficients were obtained with forward and backward digit and visual spans, visual counting, copying Rey complex figure, and block design task. The results indicated that patients with early-onset AD performed worse than late-onset AD patients on these tasks. There was no significant effect of age at onset on identification of overlapping figures, visual form discrimination, or Raven's colored progressive matrices. These findings confirm the greater attentional and visuospatial impairments in early onset patients when these confounding factors were controlled for, although no significant effect of age at onset in visuoperceptual function was observed.