Parkinson's Disease Patients' Singing Improves Voice and Swallow Impairment
Engaging in a music therapy-based singing intervention can significantly improve voice, respiratory control, and swallow while enhancing quality of life for persons with Parkinson's disease.
Parkinson's disease (PD) is the second most common neurodegenerative disorder in the United States and is estimated to affect 1% to 2% of people over the age of 65. The financial costs of PD to families, communities, and the nation, including treatment, social security payments, and lost income from the inability to work, are currently estimated at $25 billion annually. Most alarming is that over the next 20 years, the diagnosed prevalence of PD is likely to double, magnifying the economic impact of PD.1
The costs associated with PD are related to many factors, which include both motor and nonmotor aspects of the disease. The motor symptoms are the most well-known symptoms of PD. These include tremor, bradykinesia (slow movement), rigidity, postural instability, and gait disturbance. However, there are many additional motor and nonmotor symptoms, such as swallow impairment, speech impairment, cognitive impairment, depression, and autonomic dysfunction that have repeatedly been shown to have a tremendous impact on quality of life (QOL).2,3 All of these symptoms in combination limit independence and social and recreational activities, and lead to increased reliance on the health care system.4
Unfortunately, nearly 200 years after PD was discovered, the struggle to find a cure continues. Current pharmacological and surgical treatments are rooted in a physiological approach to disease and therapy, are not without risks or side effects, and do not fully address all of the problems associated with PD, such as voice and swallow impairment. Indeed, nearly 90% of individuals with PD have voice impairments, and difficulties in breathing, airway protection, and swallowing are the primary factors leading to death in patients with PD.5,6 There is a need to explore new therapies in efforts to reduce the economic burden of PD, as well as to treat significant symptoms of PD, such as voice and swallow, that do not respond to current treatments.
Voice and Swallow in PD
In particular, laryngeal muscle control is involved in voice production, respiratory control, and swallowing. To produce a vocal sound, the laryngeal muscles are involved in keeping the vocal folds in the midline so that vibration can occur, and a sound is produced. In addition, the accurate timing of the laryngeal muscle group is involved in the rapid and precise control of voice onsets and offsets. Laryngeal muscles also play a role in respiratory control. These muscles provide active vocal fold opening to enhance airflow during inspiration and partial closing to reduce airflow during expiration. Finally, for swallow, the laryngeal muscles elevate the larynx to protect the airway and allow food or liquid to pass through the pharynx.8 Thus, altered control of this muscle group may lead to many complications in persons with PD.
Along with altered neural control of the laryngeal muscle group, research has revealed impaired neural control of additional muscle groups that also contribute to impairments in voice, respiratory control, and swallow in persons with PD. Previous research has revealed decreased lip and tongue range of motion, reduced amplitude and peak velocity of jaw movements, and reduced respiratory capacity and coordination of respiratory muscles in persons with PD. Taken together, altered neural control of the laryngeal, facial, and respiratory muscles may result in reduced vocal intensity, monopitch, monoloudness, reduced vocal pitch, a harsh breathy voice, prosodic insufficiency, and imprecision with consonants, all of which are characteristics of voice impairment in persons with PD.9-11
Individuals with PD may also develop orpharangeal dysphagia—difficulty swallowing—due to altered neural control of the laryngeal, facial, and respiratory muscle groups. Due to decreased laryngeal elevation and glottis closure, foreign material such as thin liquid enters the lungs, often undetected by the patient. This is further complicated by the lack of respiratory muscular strength and reduced vital capacity (the maximum amount of air a person can expel from the lungs) needed to cough and remove foreign material from the lungs. The result is life-threatening pneumonia, a leading cause of death in PD.6,12-14
While research has well characterized the impairments in voice and swallow in persons with PD, what remains most alarming is that there is a high prevalence of voice and swallow impairment in persons with PD (up to 90%).15 Yet medication and surgical intervention (eg, deep brain stimulation) do not effectively treat voice and swallow impairments found in individuals with PD. Furthermore, while there are several speech therapy options available, it is estimated that only 3% to 4% of patients with PD undergo speech therapy.16,17 It may be that current therapy approaches have been impairment focused, treating either voice only or swallow only but not both. In addition, other areas such as QOL are sometimes overlooked.18 Progressive voice, respiratory control, and swallow impairment negatively influence QOL and can thus contribute to reduced adherence to continued therapy exercises following treatment. There remains a need for a treatment that simultaneously targets voice impairment, respiratory control, and swallow function while impacting QOL and is engaging for persons with PD to increase compliance.
Singing in PD
Previous studies investigating singing in persons with PD are limited and equivocal. Some results have demonstrated improvements in speech intelligibility and increased vocal intensity as well as singing quality and vocal range, while others found no significant effects of singing on vocal outcome measures or voice-related QOL.25-27 Differences in the dosage of the group singing sessions (60 to 90 minutes for one to three times per week), small sample size, and approach (music therapy or choral singing) may have contributed to these variable results. Moreover, no previous study has examined the effect of singing on swallow function in persons with PD.
However, research has recently been completed to determine the effects of singing on voice, respiratory control, and swallow in persons with PD. Thirty participants with PD completed eight weeks of singing therapy led by board-certified music therapists. Singing sessions included various vocal exercises targeting breath control, vocal range and intensity, and articulation, as well as group singing of familiar songs. Measures of vocal range, intensity, respiratory control, and muscle activity associated with swallow were obtained prior to and after the singing intervention. Results revealed significant improvements in both respiratory control and muscle activity associated with swallow after eight weeks of group singing therapy. While voice measures did not reach significance, there were improvements in these measures, and this remains a promising result given that PD is a progressive neurodegenerative disease. Taken together, engaging in singing may be a viable therapy to delay the progression of the disease and its impact on voice, respiratory control, and swallow in persons with PD; the author has been published on this subject.28,29
Why Music Therapy?
In addition to the focus on nonmusic behaviors that are symptomatic needs for persons with PD, the use of music therapy in rehabilitation may have additional benefits. Engaging in preferred music increases dopaminergic production in the brain, activating the reward system.30 Thus, compliance and adherence may be increased due to the reward of music. Indeed, there was a 100% compliance rate in the most recent study examining singing in PD. Finally, results from the music therapy singing intervention revealed improvements in whole health QOL along with reports from participants of feeling less depressed and stressed in a subsequent qualitative study.31 Thus, engaging in a music therapy-based singing intervention has a much broader impact improving the voice, respiratory control, and swallow while also improving compliance and QOL for persons with PD.
The Future of Care in PD
— Elizabeth Stegemöller, PhD, MT-BC, is an assistant professor in the department of kinesiology at Iowa State University in Ames. She is a neuroscientist and music therapist whose work focuses on understanding the use of music to facilitate movement and associated neurophysiology in persons with Parkinson's disease.
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