Effect of dopaminergic medication on speech dysfluency in Parkinson’s disease: a longitudinal study

Abstract

Although speech dysfluencies have been hypothesized to be associated with abnormal function of dopaminergic system, the effects of dopaminergic medication on speech fluency in Parkinson's disease (PD) have not been systematically studied. The aim of the present study was, therefore, to investigate the long-term effect of dopaminergic medication on speech fluency in PD. Fourteen de novo PD patients with no history of developmental stuttering and 14 age- and sex-matched healthy controls (HC) were recruited. PD subjects were examined three times; before the initiation of dopaminergic treatment and twice in following 6 years. The percentage of dysfluent words was calculated from reading passage and monolog. The amount of medication was expressed by cumulative doses of L-dopa equivalent. After 3-6 years of dopaminergic therapy, PD patients exhibited significantly more dysfluent events compared to healthy subjects as well as to their own speech performance before the introduction of dopaminergic therapy (p < 0.05). In addition, we found a strong positive correlation between the increased occurrence of dysfluent words and the total cumulative dose of L-dopa equivalent (r = 0.75, p = 0.002). Our findings indicate an adverse effect of prolonged dopaminergic therapy contributing to the development of stuttering-like dysfluencies in PD. These findings may have important implication in clinical practice, where speech fluency should be taken into account to optimize dopaminergic therapy.

Perfil da fluência da fala em diferentes tarefas para indivíduos com Doença de Parkinson

“…With respect to stuttering dysfluencies, the findings of this study indicated that individuals with PD presented a larger number of this type of disruption compared with those in the control group, corroborating abundant research found in the literature (1)(2)(3)(4)(5)(6)(7)(8)(9)16,(18)(19)(20)23) . Despite the consensus reported in the literature on the existence of stuttering-like dysfluencies in PD, the reasons for their occurrence are still controversial and not sufficiently clarified.…”

“…The presence of dysfluencies in the speech of individuals with PD has been discussed in several studies in the specific scientific literature (1)(2)(3)(4)(5)(6)(7)(8)(9)16,(18)(19)(20)23) . The results of the present study corroborate the findings of a study (4) which reported that individuals with PD presented a larger number of stuttering-like dysfluencies and lower speech rate when compared with those of a control group.…”

“…Some studies have suggested that speech dysfluencies are exacerbated by levodopa -a medicine used to control the motor symptoms of PD (2,3,18,19) . Another study emphasizes that the increase in speech dysfluency in PD is more closely associated with disease progression than with levodopa levels (20) .…”

“…The most common manifestations cited in these studies were repetition of sounds, syllables, and words; prolongation of sounds; inappropriate and/or excessively long pauses. Another abnormality observed was palilalia, a disorder characterized by compulsive repetition of a statement in a context of increased rate and decreased loudness (1)(2)(3)(4)(5)(6)(7)(8)(9) . In some studies, the number of stuttering disruptions presented by individuals with PD was greater than 3% of stuttered syllables, characterizing a stuttering disorder (4,6,8,10) .…”

“…Regarding speech, hypokinetic dysarthria is present in more than 90% of PD cases. The main symptoms are decreased vocal stress, monotony, hoarse and/or breathy vocal quality, reduction in spoken voice, articulatory inaccuracy, hypernasal resonance, and fluency alterations (1,3,4) . Speech dysfluencies have been reported in several studies conducted with individuals who presented hypokinetic dysarthria owing to PD.…”