Vocal dysfunction is well established in persons with older-onset Parkinson’s disease (PD), but has not been investigated in the young-onset PD (YOPD) population.  Voice deficits associated with older-onset PD mirror the characteristics of vocal aging, suggesting that our current knowledge base of laryngeal dysfunction in the PD population is confounded by aging effects.  The purpose of this study was threefold: (a) to examine perceptual voice characteristics and the potential impact of voice symptoms on quality of life; (b) to compare YOPD and healthy control (HC) speakers’ performance on two routinely used clinical tasks (sustained vowel phonation and laryngeal diadochokinesis); and (c) to experimentally manipulate and compare speakers’ performance in producing phonatory offset-onset gestures as reflected in four phonetic contexts (each eliciting a different mechanism)  across three speaking modes. Twelve YOPD speakers and twelve healthy control (HC) speakers participated. YOPD speakers reported voice symptoms of hypophonia, tremor, hoarseness, monotone, and impaired speech intelligibility. They demonstrated a mild to moderate voice handicap. Findings revealed no speaker group differences for speech intensity on sustained vowel phonation and reading tasks.  YOPD speakers demonstrated a significantly decreased rate of syllable repetition and used a significantly greater number of pauses during production of one of two laryngeal diadochokinetic tasks.  Acoustic measures associated with mechanisms of phonatory offset-onset demonstrated trends of speaker group differences, suggesting that YOPD speakers have impaired voicing control for mechanisms of phonatory offset-onset not associated with oral constriction. Intra-speaker group variability was observed for YOPD speakers. Inspection of speaker groups’ performance across speaking modes suggested a disruption in the habitual setting of laryngeal posture in YOPD speakers; namely, they use a laryngeal postural setting that is similar to that observed in HC speakers when speaking in an aspirant or breathy voice mode. Speech masking facilitated a speaking mode change in YOPD speakers and could provide an effective and efficient treatment method for training persons with YOPD to speak in a projected mode.  Vocal dysfunction is associated with YOPD and voice symptoms can appear early in the disease process, sometimes preceding onset of limb symptoms. Persons with YOPD should be routinely assessed for vocal dysfunction.


The word parkinsonism refers not to a particular disease but to a commonly recognized neurological condition marked by a characteristic set of features that include a resting tremor of the hands and legs, muscular stiffness (e.g., rigidity), and slowness of body movement (i.e. bradykinesia) (Duvosin & Sage, 1996).  The most prevalent type of parkinsonism is known as idiopathic Parkinson’s disease (PD) meaning the cause is unknown.  Typically the onset of PD occurs in adult life, having a peak incidence between 50-69 years of age with an average onset in the sixth decade (Hoehn & Yahr, 1967; Zetusky, Jankovic, & Pirozzolo, 1985).  It is, therefore, considered a disease of the elderly.  Giovannini et al. (1991) speculated that the concept of PD as a disease of the elderly was so widely accepted by physicians that patients younger than 50 years who presented with parkinsonian features were diagnosed with a parkinsonian-like syndrome, suggesting that it was a different disease.  Recent advancements in research have led to the diagnosis of PD in patients who develop parkinsonian symptoms or signs in young adulthood or prior to the age of 50 years.  These young patients have arbitrarily been diagnosed with early-onset Parkinson’s disease (Arevalo,

Jorge, Garcia, Scipioni, & Gershanki, 1997; Boxall, 1994; Giovannini et al., 1991;

Muthane, Satishchandra, & Subhash, 1993) or young-onset Parkinson’s disease

(Gibb & Lees, 1988; Pantelatos & Fornadi, 1993; Quinn, Critchley & Marsden,

1987; Schrag, Ben-Shlomo, Brown, Marsden & Quinn, 1999; Stern et al., 1991). 

Clinical studies differ in their definition of the age span inclusion of young-onset

Parkinson’s disease (YOPD). Some have defined their cohort to include patients whose initial symptoms developed prior to the age of 40 years (Gibb & Lee, 1988; Pantelatos & Fornadi, 1993; Quinn, Critchley & Marsden, 1987; Schrag et al., 1999; Stern et al., 1991), whereas others have investigated young onset and earlyonset using an upper age limit of prior to age of 50 years (Watts, 1997). Those who have symptoms appearing earlier than age of 50 years are referred to as juvenile parkinsonism; and when compared with other forms of parkinsonism, juvenile parkinsonism may represent a different clinical entity, presenting with dystonia (Muthane et al., 1994) and a higher familial incidence in comparison with idiopathic PD (Quinn et al., 1987).

The majority of individuals with Parkinson’s disease develop voice and speech abnormalities during the course of their disease progression. The reported incidence of voice and speech disorders in PD ranges from 73% to 89%  (Hirose,

Kiritani, Ushijima, Yoshioka, & Sawashima, 1981; Logemann, Fisher, Boshes, & Blonsky, 1978; Ramig, Countryman, Thompson, & Horii, 1995).  Logemann and colleagues studied 200 nonmedicated individuals with PD who were mostly of idiopathic onset but included some post encephalitic cases who developed PD subsequent to a viral flu epidemic ( Logemann, Blonsky, & Boshes, 1973;

Logemann, Boshes, Blonskey, & Fisher, 1977; Logemann, Fisher, Boshes, &

Blonsky, 1978).  The cohort represented all five stages of disease progression (Hoehn & Yahr, 1967). The investigators noted a high incidence (89%) of early onset of voice disorders in individuals with PD, while only forty-five percent had abnormal articulation.   Other speech abnormalities such as hypernasality and fluency disorders (e.g., repetition of syllables, abnormally long pauses, and abnormally long syllables) were present but less frequent. They did not measure prosodic disturbances involving intonation nor did they indicate the age of the individuals studied.   Although published studies do not report quantitative data to estimate the functional impact of these PD disorders, anecdotal accounts suggest that these voice and speech deficits have adverse effects on the individual’s communicative effectiveness, as well as economic, social, and psychological wellbeing (Barbeau, Dushay & Spiegel, 1965; Habermann, 1996; Marr, 1991;

MacCarthy, & Brown, 1989; Mutch, Strudwick, Roy & Downie, 1986; Ramig,

Countryman, O’Brien, Hoehn, & Thompson, 1996; Yorkston, Bombardier, & Hammen, 1994). 

 Other studies have corroborated the high incidence of voice disorders and early appearance of voice disorders.  Stewart et al. (1995) reported that 12 persons, assessed in the early stages of the disease, had at least two characteristics of a voice disorder. Interestingly, 8 of the 12 individuals were not aware of their vocal dysfunction.  Hanson, Gerratt, and Ward (1984) reported that 30 of their 32 PD participants had vocal dysfunction (described as weakness), and that the degree of articulatory dysfunction did not correlate with voice abnormalities.  Furthermore, the occurrence of voice symptoms preceded the onset of limb symptoms in some individuals (Hanson et al, 1984; Tetrud, 1991).  In fact, Tetrud (1991, p. 70) reported, “long before the disease is diagnosed, family members and friends of a prospective patient may notice the voice has become softer or slightly hoarse.”   He advocated  the development of an automated voice and speech analysis technique to provide a method of identifying individuals with pre-clinical disease.  “This would permit the institution of protective therapy before the disease becomes clinically manifest. “ (Tetrud, 1991, p. 71). In summary, voice disorders are a frequently occurring problem in PD.  The effects of age on PD-related voice disorders are uncertain.

Typical vocal manifestations of PD include (a) breathy or rough voice quality (Logemann et al., 1978; Hanson, Gerratt, & Ward, 1984); (b) reduced loudness (hypophonia) (Ramig et al.);  (c) voicing control deficits that include difficulty producing rapid phonatory offset-onset during speech (Ackermann &

Ziegler, 1991; Canter, 1965; Forrest et al., 1989; Kent & Finley Kent, 2000); and (d) reduced pitch inflection and reduced control in altering pitch during speech segments (hypoprosodia) (Caekebeke, Jenneknes -Schinkel, van der Linden,

Buruma & Roos, 1991; Robertson & Thompson, 1984; Scott & Caird, 1984). Speech timing deficits involving speech rate disturbances and the use of longer and more frequent pauses have been reported by several investigators (Hammen &

Yorkston, 1996; Metter & Hanson, 1986; Pitcairn, Clemie, Gray, & Pentland, 1990; Solomon & Hixon, 1993) and are most likely attributed to phonatory deficits. Vocal tremor may also occur but is frequently not audible (Gath & Yair, 1988).  Taken together, investigations of speech deficits in PD suggest that a large portion of these deficits involve the phonatory system.

Voice deficits associated with PD markedly mirror the characteristics of vocal aging, suggesting that our current knowledge base of laryngeal dysfunction in the PD population is confounded by aging effects (Hori & Ryan, 1981; Huntley,

Hollien, & Shipp, 1987; Linville & Korabic, 1986; Ptacek et al., 1966).  Perceptual characteristics of the aged voice have included (a) inappropriate pitch levels, (b) hoarseness/roughness, (c) vocal tremor and increased phonatory breaks, (d) breathiness, and (e) reduced loudness (Linville, 1996; Mysak & Hanley, 1958; Shipp & Hollien, 1969).  These perceptual features have been further documented with parallel acoustic observations of (a) changes in fundamental frequency (Fo), whereby males show an increase in Fo and females show a decrease (Higgins &

Saxman, 1991; Hollien & Shipp, 1972; Linville, 1987, 1992; Mueller, Sweeney, & Baribeau, 1984; Ramig & Ringel, 1983; Stoicheff, 1981); (b) increased short-term acoustic perturbations of jitter and shimmer (Brown, Morris, & Michel, 1989; Decoster & Debruyne, 1997; Ramig, 1983; Ramig & Ringel, 1983); (c) increased phonatory instability or long-term acoustic perturbations (i.e. tremor, subharmonics) (Decoster & Debruyne, 1997; Linville, 1996; Mysak & Hanley,

1958; Ramig & Shipp, 1987; Shipp & Hollien, 1969); (d) increased spectral noise 

(Decoster and Debruyne, 1997); and (e) reduced vocal intensity (Baker, Ramig, Sapir, Luschei, & Smith, 2001; Stathopoulos & Sapienza, 1993). Although respiratory and supraglottal systems contribute to these changes, tissue changes in the composition of the extracellular matrix, the muscular changes in the larynx, and a loss of neural control  are believed to be the primary contributors to vocal aging (Hoit & Hixon, 1987; Sonies, Stone, & Shauwker, 1984).  Therefore, separating disease-related versus age-related changes in phonatory function is difficult when one studies only an older-onset cohort of PD persons.

Need for Study

Studies of vocal dysfunction associated with PD have included only aged persons or have grouped data for both  aged individuals and persons with youngonset Parkinson’s disease (YOPD).  There are no published studies reporting vocal dysfunction in a cohort limited only to individuals with YOPD who are nongeriatric (under the age of 60 years). Therefore, it is uncertain if the vocal dysfunction observed in PD is attributable solely to the disease process or is confounded by aging effects.

It is important to assess the functional impact of vocal dysfunction in persons with YOPD to determine the need for voice treatment. Previous studies have not employed sensitive psychometric tools to probe psychosocial consequences of voice disorders, such as emotional, functional, and physical restrictions placed on daily living.  In comparison with an older-onset cohort, it is likely that this YOPD cohort views their vocal dysfunction as having greater negative impact on their quality of life, given the economic need of the younger person to maintain employment.

Exploration of hypotheses regarding underlying mechanisms that may influence the vocal dysfunction in PD is critical to the development of effective treatment programs.  One hypothesis is that the multidimensional changes of breathy voice quality and hypophonia reported in PD speakers suggests a change in the speaker’s voice mode or habitual setting of the laryngeal posture. Recent evidence suggests that sensory processing deficits associated with the neural degenerative process in PD may disrupt the internal regulation of vocal loudness in PD participants (Ho, Bradshaw, Iansek, & Alfredson, 1999; Ho, Iansek, & Bradshaw, 1999).  That is, people with PD perceive their normal conversational voice as loud when it actually is soft because of a deficit in their internal regulation of speech volume. As such, their resulting speech intensity is insufficient for effective communication. Furthermore, evidence suggests that PD speakers use greater respiratory drive and oral constriction to compensate for glottal insufficiency.  This results in a greater effort than that used by healthy speakers (Baker et al., 2001). To avoid the sense of a greater effort, speakers with PD may adjust their habitual laryngeal setting or mode to one that healthy speakers use when they are talking in a quiet or confidential voice (e.g., talking in a library or telling a secret so as not to be overheard by others). 

Recent behavioral treatments for PD-related voice disorders have focused on altering voice mode by increasing loudness or physical effort when talking

(Ramig, 1995a, 1995b; Ramig, 1997, 1999; Ramig, Bonitati, Lemke, & Horri,

1994; Ramig, Countryman, O'Brien, Hoehn, & Thompson, 1996; Ramig,

Countryman, Thompson, & Horri, 1995; Ramig & Dromey, 1996; Ramig & Verdolini, 1998). In the Lee Silverman Voice Treatment    (LSVT            ), the clinician cues the patient to “think loud.” However, external cueing like “think loud” may impose a cognitive load that is difficult for the person with PD to remember.  Although the efficacy data in one study comparing pre- to post-treatment changes in vocal intensity showed a significant increase for sustained phonation (14 dB) and reading (12 dB), changes in conversational speech (although statistically significant) were substantially less (5 dB) (Ramig et al., 1995).  These results and anecdotal comments from persons who are treated with the LSVT          , and have stated they have difficulty generalizing their ‘loud speech’ outside of the clinical setting, suggests a need for alternative cueing mechanisms to facilitate normal loudness when speaking. Speech masking also serves as an external cueing technique for increased vocal effort in PD, and may impose fewer cognitive constraints (Adams & Lang, 1992). However, research evidence pertaining to the use of masking noise has been limited, and the efficacy of masking noise in treating vocal dysfunction in speakers with PD is uncertain because prior studies have been confounded by aging and hearing loss (Adams & Lang, 1992; Ho, Bradshaw et al., 1999). Therefore, further studies are needed to determine the effectiveness of speech masking in speakers with PD.

Statement of Purpose

Vocal dysfunction has not been investigated in a cohort of YOPD individuals. Therefore, the main purpose of this study was to delineate the multidimensional changes in voice characteristics in these individuals, who represent a form of PD uncontaminated by aging effects, and to determine the impact of such dysfunction on quality of life.  Additionally, this study sought to identify underlying vocal deficits as evidenced in traditional clinical tasks of sustained phonation and laryngeal diadochokinesis (L-DDK).  Finally, this study manipulated speaking contexts by comparing a speaker’s habitual or conversational voice to use of (a) a confidential voice elicited by external verbal cueing to speak in a breathy, aspirant voice,  and (b) a projected voice elicited by external cueing with speech masking (to elicit changes in vocal effort associated with speaking in a loud, projected voice). The purpose of this experimental manipulation was to determine the effects of voice mode manipulation on speech intensity and phonatory offset-onset control.