Language impairment in the moderate stage of dementia due to Alzheimer's disease.

Background: During the moderate stage of dementia due to Alzheimer's disease (AD), language disorder is more evident and it impacts on communication. An overview of language impairment could be helpful to find compensatory communication strategies for these patients.

Objective: To identify all language impairments among patients with moderate-stage of AD.

Methods: 20 patients diagnosed with probable AD based on the criteria of the NINCDS-ARDRA, with a MMSE score of 13-23 points and CDR=2, who were undergoing treatment for AD with therapeutic doses of acetyl cholinesterase inhibitors, were assessed using the Boston Diagnostic Aphasia Examination (BDAE), a test that provides a broad assessment of language. The results were compared with the performance of a normal population.

Results: The patients assessed in this study presented normal scores for oral and written word recognition, repetition, mechanics of writing, primer-level dictation and spelling to dictation but also had impairment at most levels of linguistic processing, in oral and written comprehension and production. In general, as expected, the tasks relying on access to the mental lexicon were most significantly affected. However, they performed well in the naming task, in which semantic cues were presented. Moreover, the patients assessed in this study had better performance in written comprehension tasks than in oral ones.

Conclusion: The severity of the language impairments was not homogenous, with some linguistic abilities more impaired than others. The abilities that were found to be preserved can help to guide strategies for aiding in communication at this stage of AD.