Comprehensive language testing shows a strong relationship between overall severity of cognitive decline and language deficit. Moreover, the language performance can be affected also by neuropsychiatric symptoms of dementia.

To detect the language deficits in sentence comprehension in patients with MCI and dementia and to determine the relationship between them, the severity and the structure of cognitive impairment and independently between them and BPSD.

In the sample of 46 cognitively declined patients (MCI and dementia, majority of them with Alzheimer's disease), we evaluated the severity and the structure of cognitive impairment by means of MoCA instrument, language deficits by our own sentence comprehension test and BPSD by means of NPI-Q.

The average performance in the sentence comprehension test was about 90% of normal in the group of MCI patients, about 75% in mild, about 60% in moderate and only about 20% in the group of severe dementias. According to individual cognitive domains, their impact on language performance was different. We found a strong correlation between the overall severity of BPSD and the language performance, too.

At earlier stages of cognitive disorders/dementias, the language specific test should be used to discover comprehension deficits, because at the simple level of word the language skills are preserved. BPSD are also associated with language deficits even when the severity of dementia is controlled for. Identification of these communication disturbances can help to detect cognitive decline earlier and to start preserving treatment in time.