Abstract Objective: The use of cohesive devices makes discourse comprehend. However, in the discourse of senile dementia of the Alzheimer's type (SDAT) participants, the lack of the use of cohesive devices hinders effective communication. The present study aims to investigate cohesion in the discourse of SDAT participants. Understanding how these people manage their interactions may lead to suitable approaches for them. Method: The methodology of this quantitative research was ex post facto type. The present study has been performed in one of the nursing home in Kermanshah in 2019. And also, the statistic population of this study included 20 participants (10 SDAT participants and 10 normal elderly participants (NE)) who were matched based on age (63-75 years old), gender, illiteracy, and Kurdish language (Kalhori dialect) speaker. To determine the severity of dementia, the Clinical Dementia Rating Scale (CDR) was performed. Then, the collected interviews were transcribed and coded. The data were analyzed based on Halliday and Hasan's theory (1976) and independent t-test was used to obtain the statistic results. Results: The findings indicate significant differences between groups using grammatical cohesive devices, such as reference (p=0.006), conjunction (p=0.004), ellipsis (p=0.007), and substitution (p=0.426) and lexical cohesive devices such as the same word (p=0.006), synonym (p=0.012), superordinate (p=0.001), general word (p=0.002), and collocation (p=0.387). Conclusion: The results show that grammatical and lexical cohesive devices are used less in the discourse of SDAT Kurdish speakers. However, in the discourse of both SDAT and NE groups, grammatical cohesive devices have more frequency than lexical cohesive devices.
