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Background: Diadochokinetic rates tasks are frequently used for the assessment of diadochokinesia (DKK) in young and elderly adults. However, there is scarce research on healthy elderly adults over 65 years old, and little is known about the effect of different types of stimuli (non-words/real words) in this specific population. Furthermore, the current research supports significant language variations, highlighting the need for language-specific norms. Aims: To investigate the effect of age, gender and type of stimuli (non-words versus real words) in DDK rates in healthy elderly adults of over 65 years of age, and to provide normative data for the Greek language. Methods & Procedures: The participants were 791 healthy monolingual Greek-speaking adults (531 adults, aged 20-39 years; 157 participants aged 65-74 years; and 103 participants aged over 75 years). All participants were monolingual speakers of Greek and had normal hearing acuity, which allowed them to understand and follow instructions. Participants with a medical condition, which would affect DDK rates' performance, were excluded from the study. The time-by-count method was used, and all participants had to repeat as accurately and fast as possible: (1) four disyllabic non-words (/'gaba/, /'taka/, /'kata/, /'baga/); (2) four disyllabic real words (/'kapa/, /'tapa/, /ka'la/, /'paka/); and (3) two trisyllabic non-words (/'pataka/, /'badaga/). All responses were recorded and the speech samples that did not include at least 5 s of correct repetitions were excluded from the analysis. Outcomes & Results: Age affected DDK rates significantly, with older adults achieving slower DDK rates for all speech stimuli (non-words/real words). Gender did not have an effect on the performance of DDK rates. The type of speech stimuli affected DDK rates significantly for all age groups. Analytically, trisyllabic non-word stimuli were articulated more slowly than disyllabic non-word stimuli, and real words were produced faster than non-words. A linear regression analysis revealed that only the repetition of non-words predicted 68.4% of the performance on the repetition of trisyllabic non-words. Conclusions & Implications: The above results complement prior research, which supports that real word stimuli yield faster performance than non-word stimuli. Clinicians should keep in mind that age, language and type of stimuli (non-words/real words) affect significantly the performance of DDK rates, as well as the fact that different types of stimuli tap distinct underlying levels of speech. The current research highlights the need for language-specific norms for different populations.

Background: Diadochokinetic (DDK) rate tasks are extensively used in the evaluation of speech disorders; however, it is unclear how the different types of speech stimuli affect DDK rate performance. Aims: To investigate the effect of age, gender and type of stimuli (non‐words versus real words) on the DDK rates in individuals across the lifespan and to provide normative data for Greek. Also to examine the discrimination ability of the speech DDK stimuli administered (non‐words and real words) based on a dual DDK assessment protocol using a polytomous item response theory (IRT) model. Methods & Procedure: The participants were 1747 monolingual Greek speakers (376 children, aged 4–17 years; and 1371 adults, aged 18–90+ years). All participants had normal hearing acuity which allowed them to understand and follow instructions. Participants with a medical condition or a language disorder which would affect DDK rate performance were excluded from the study. The time‐by‐count method was used, and all participants had to repeat as accurately and fast as possible: (1) four disyllabic non‐words (/'gaba/, /'taka/, /'kata/, /'baga/), (2) four disyllabic real words (/'kapa/, /'tapa/, /ka'la/, /'paka/) and (3) two trisyllabic non‐words (/'pataka/, /'badaga/). All responses were recorded and the speech samples that did not include at least 5 s of correct repetitions were excluded from the analysis. Outcomes & Results: Age affected significantly DDK rates with performance increasing gradually until approximately the age of 40 and then gradually decreasing. Gender had no effect. Overall, there was a significant advantage of disyllabic real word stimuli over disyllabic non‐word stimuli and of trisyllabic non‐word stimuli over disyllabic non‐word stimuli on DDK rates performance. IRT analysis suggested that the data fit the polytomous model reasonably well and all DDK stimuli (real words and non‐words) showed a strong relationship (loadings > 0.50) with the latent trait. Conclusions & Implications: The current study complements prior research which supports that age and type of stimuli significantly affect DDK rates performance. It is the first study, that testifies to the benefit of real‐word stimuli over non‐word stimuli on DDK rates across the lifespan in a large representative sample. The implementation of IRT analysis provides empirical evidence about the discrimination ability of the DDK stimuli administered and confirms the reliability of this dual DDK assessment protocol. These findings are valuable for clinicians who work with motor speech disorders. WHAT THIS PAPER ADDS: What is already known on this subject: Age, type of stimuli (real words versus non‐words) and language significantly affect DDK rates performance. Current research strongly suggests the administration of language‐specific norms since language‐dependent features seem to have a noteworthy effect on the DDK rates, but scarce evidence exists about the discriminatory ability of the DDK speech stimuli commonly administered. What this study adds to the existing knowledge: Conflicting findings have been reported about the effect of different types of DDK speech stimuli (real words and non‐words) but no study to date has evaluated their discriminatory abilities. The current study is the first to implement a polytomous IRT model to examine this issue. This is also the first study to attempt an investigation of the effect of types of stimuli (real words versus non‐words) on a large representative sample across the lifespan (4–90+ years) and to provide normative data for Greek. What are the practical and clinical implications of this work?: The present study offers concrete evidence about the advantage of real‐word stimuli over non‐word stimuli in Greek, as well as normative data for the Greek‐speaking populations. Moreover, the IRT analysis testifies to the discriminatory ability of real‐word and non‐word stimuli affirming the reliability of the present dual DDK assessment protocol as a psychometrically sound measure of DDK ability. The above has significant value for clinicians who work with individuals with motor speech disorders as the protocol can help them with the diagnosis and differential diagnosis of motor speech disorders. [ABSTRACT FROM AUTHOR]