Objectives: This study aimed to evaluate some speech disorders in groups of patients with Lewy body spectrum disorders (LBSD), compare the groups in order to identify the possible causes of the disorders, and improve the given patients’ quality of life by helping them manage the development of speech disorders and rehabilitation of them. Methods: The present case-control study was performed to examine a total of 40 individuals, including 10 healthy people as controls and 30 patients with a range of LBSD diagnosed based on the criteria for cognitive neurological and motor disorders published by the University of Pennsylvania Department of Neurology. Results: The four groups were similar in age and sex distribution and were not statistically and significantly different. The highest score of short mental state test (MMSE) was obtained for the control group. Parkinson’s patients with dementia spent the longest time to tell the story. The highest number of sentences was also produced by the Parkinson’s disease (PD) group. The control group faced the least number of vocabulary retrieval problems when narrating the story. On the other hand, the most frequent word retrieval problem was observed in dementia with Lewy bodies, followed by Parkinson’s disease with dementia (PDD). There was a significant difference between the control group with dementia and the Lewy body in terms of frequency distribution of action and search theme. There were also significant differences among four groups regarding the global and local connectedness of storytelling as well as the number of keywords used. Conclusions: In sum, a considerable speech disorder was observed in patients with LBSD, which was more evident in two groups with dementia. Therefore, dementia may have been the main cause of these impairments.

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