Patient Profiling: Determining the Effects of Patient Factors on Vocal Fatigue

Summary:

Objectives.

The phenomenon of vocal fatigue and the types of patients that are at greatest risk for vocal fatigue are not fully understood. The goal was to investigate patient profiles such as voice disorder type, demographics (age and gender), singing identity, interoceptive awareness, and psychosocial impacts on the severity of vocal fatigue.

Study Design.

Prospective cohort study.

Methods.

Ninety-five subjects with voice disorders were asked to complete Part 1 of the Vocal Fatigue Index (VFI-Part1), the Voice Handicap Index-10 (VHI-10), and the Multidimensional Assessment of Interoceptive Awareness, version 2 (MAIA-2). The effects of voice disorder type (structural, neurological, functional), psychosocial impact, age, gender, self-reported singing identity, and interoceptive awareness on self-perceived vocal fatigue (VFI-Part1) were determined using multivariate linear regression.

Results.

Vocal fatigue had a significant psychosocial impact on patients with voice disorders, as measured by the VHI-10 (P < 0.001). However, there were no significant effects of vocal fatigue across any of the three voice disorder types (P’s > 0.05). Age (P = 0.220), gender (P = 0.430), and self-identified singing experience (P = 0. 360) also did not have significant effects on vocal fatigue. Additionally, there were no significant relationships between interoceptive awareness MAIA-2 sum scores (P = 0.056) or any of the MAIA-2 sub-scores (P’s > 0.05) and vocal fatigue severity (VFI-Part1).

Conclusion.

Vocal fatigue has a significant psychosocial impact on patients with voice disorders. However, patient profiles, including voice disorder type, patient age, gender, singing identity, and level of interoceptive awareness do not appear to play a major role in vocal fatigue symptom reporting. These findings suggest caution should be exercised when attributing patient profiles to vocal fatigue presentation and severity. Studying pathophysiological mechanisms underlying vocal fatigue may help better distinguish unconscious bias in patient profiling from the etiology and severity of vocal fatigue.

INTRODUCTION

Vocal fatigue is defined as tiring of the voice and is often associated with symptoms of increased vocal effort and paralaryngeal discomfort and tightness.^1,2 Aberrant vocal quality (eg, vocal strain, breathiness) and difficulties with vocal intensity may also be associated with symptoms of vocal fatigue, especially in the context of high vocal demands—although vocal fatigue may have more to do with the feel of the voice than the sound of the voice.^1,3,4 Vocal fatigue can be debilitating and has known occupational consequences.^5,6 Vocal demands are highly individualized to each patient making vocal fatigue notoriously heterogeneous in nature.^3,6

There has been extensive research on the consequences of occupational voice use and increased vocal demands in the context of vocal fatigue in professional voice users, with teachers being the population most commonly studied.^7,8 Relationships between environmental factors (eg, room acoustics, background noise) and implications of vocal production demands (eg, vocal pitch and intensity) have also been studied.^2,7 However, individual patient factors (ie, patient profiling) such as age, gender, voice disorder type, self-perceived severity of voice impact and quality of life, singing identity, and interoceptive awareness have been far less studied. These intrinsic patient factors could explain, at least in part, the heterogeneity in vocal fatigue onset, presentation, and perpetuation of vocal fatigue symptoms. Understanding the contribution of patient factors collected as personal health information during a voice evaluation to perceptions of vocal fatigue can facilitate the identification of the patients who are at greatest risk. Elucidating the relationships between patient profiles and self-perceived vocal fatigue can also assist clinicians in the anticipation of their effects, thus allowing clinicians to determine patients’ prognosis and need for treatment more accurately.

Although patient-specific factors like age and gender are often reported in research studies on vocal fatigue,^7,9 relationships between age, gender, and vocal fatigue severity have not been interpreted in patients with voice disorders. Considering fatigue coincides with the depletion of the body’s homeostatic reserves and has similar psychological and physical functional impairments to individuals with frailty and senescence,¹⁰ relationships between age and vocal fatigue severity are important to understand. Gender may also influence how patients perceive their vocal fatigue severity levels. Several studies have suggested that the severity of vocal fatigue may be higher in cisgender women,^11–14 but the majority of this work has been conducted in professional voice users and not in patients with voice disorders. Furthermore, although clinical wisdom suggests women are at higher risk for vocal fatigue, this claim is not well supported in the literature.

The type of voice disorder and its impact on quality of life also requires investigation. Patients with functional,^4,9 neurological,¹⁵ or structural^9,16 voice disorders may report vocal fatigue differently from each other due to disparate underlying pathophysiological mechanisms that can result in clinical presentations of vocal fatigue. However, relationships between voice disorders and vocal fatigue severity have not been investigated. Patients who report more severe psychosocial impacts of their voice disorder may also report vocal fatigue differently than those who do not experience debilitating effects.

Whether patients self-identify as a singer and whether they have a singing background, singing experience, or formal singing training may also influence vocal fatigue responses, especially in the context of interoception—or the individual’s consciousness of their physiological state.¹⁷ Singing experience or training may influence how in-tune the patient is with their vocal mechanism and their internal milieu with voice use. Vocally healthy singers were previously found to have higher interoceptive awareness compared to individuals with no singing background.¹⁸ An individual’s ability to assess their own physiological state regarding their assessment of their own voice symptoms (eg, interoceptive awareness) could have a powerful impact on how patients perceive their vocal fatigue as well. This question is especially relevant considering vocal fatigue has previously been proposed to be a self-perceptual sensory construct^3,7 and interoceptive awareness metrics assess relationships between body sensations and emotional appraisal. Furthermore, previous work found patients with certain types of voice disorders may differ in their sensory and emotional experiences within interoceptive awareness constructs.¹⁹

One of the most commonly used assessments of vocal fatigue severity is the Vocal Fatigue Index (VFI).²⁰ The VFI is a psychometrically validated 19-item self-administered questionnaire that asks individuals to rate the severity of their vocal fatigue symptoms. It is measured on a 5-point Likert scale with 0 = never, 1 = almost never, 2 = sometimes, 3 = almost always, and 4 = always. The VFI is divided into three parts (factors). Nanjundeswaran et al²⁰ found that Part 1 of the VFI (herein referred to as VFI-Part1) can distinguish pathological levels of vocal fatigue in disordered voices from typical vocal fatigue experienced by occupational voice users after heavy vocal demands. Because we were interested in pathological vocal fatigue in patients with voice disorders, VFI-Part1 was used to determine these relationships. Specifically, the effects of voice diagnosis type (neurological, structural, functional), voice disorder impact based on the Voice Handicap Index-10 (VHI-10), patient demographics (gender, age), singing identity (yes or no), and interoceptive awareness were all assessed potential factors that could impact VFI-Part1 responses.

The purpose of this study was to investigate the role of different patient factors on self-perceived severity of vocal fatigue and determine relationships between vocal fatigue severity and patient profiles. We aimed to answer the following questions: (1) Does the type of voice disorder (functional, neurological, and structural) impact vocal fatigue severity, as measured on the VFI-Part1? (2) Does the severity of the voice disorder impact (as measured on the VHI-10) predict how individuals respond on the VFI-Part1? (3) Do patient demographics (age and gender) influence responses on the VFI-Part1? and (4) Does singing experience and interoceptive awareness predict how patients will respond to the VFI-Part1?

METHODS

Study protocol

The study was approved by the University of Texas Southwestern Medical Center Institutional Review Board. Ninety-five (n = 95) participants who came to the UT Southwestern Center for Voice Care for their initial voice assessment completed three questionnaires: The VFI-Part1, the VHI-10, and the Multidimensional Assessment of Interoceptive Awareness, version 2 (MAIA-2). A speech-language pathologist and medical assistant at the UT Southwestern Center for Voice Care administered the three questionnaires at the beginning of each patient’s initial visit, prior to them receiving a diagnosis. Patients were provided with the forms on a clipboard, given a writing utensil, and instructed to fill out the questionnaires to the best of their ability as they related to their voice symptoms. Participants were informed that the VFI-Part1 and the VHI-10 indices are given to all new voice patients as part of standard-of-care procedures and that the goal of the MAIA-2 was to better understand patient experiences. Completing all three questionnaires took no more than 20 minutes, and thus mental fatigue potentially influencing how patients rated their vocal fatigue was of little concern.

The VHI-10 is a 10-item self-administered questionnaire that asks individuals to rate how their voice problems affect their quality of life and how frequently they experience it.²¹ The scale is measured on a 5-point Likert scale (0 = never, 1 = almost never, 2 = sometimes, 3 = almost always, and 4 = always). The MAIA-2 is an 8-scale state-trait questionnaire consisting of 37 items that measure an individual’s conscious awareness of interoception through self-reporting.²² The scale is measured on a 6-point Likert scale (0 = never; 5 = always), and includes eight subscales: (1) Noticing (Q1–4), (2) Non-Distracting (Q5–10), (3) Not-Worrying (Q11–15), (4) Attention Regulation (Q16–22), (5) Emotional Awareness (Q23–27), (6) Self-Regulation (Q28–31), (7) Body Listening (Q32–34), and (8) Trusting (Q35–37).

The eight subscales on the MAIA-2 provide further information about specific constructs within self-perceived interoceptive awareness. Noticing involves the awareness of bodily sensations. Non-distracting is when an individual tends to sensations of pain or discomfort in their body rather than ignore or distract from them. Not-Worrying is the tendency to not concern oneself with emotion or appraisal of pain or discomfort. Attention Regulation is the ability to attend to bodily sensations. Emotional Awareness is the capacity to connect body sensations to an emotional state. Self-Regulation involves the ability to regulate emotions that arise from attending to bodily sensations. Body Listening is the capacity to be tuned into one’s body for insight. Trusting is the ability to experience one’s body as safe and trustworthy.²²

Participants were asked to circle the number that best described the severity of each vocal fatigue-related experience for all 11 items on the VFI-Part1, the number that best aligned with the impact of their voice disorder on the VHI-10, and to complete answers related to their self-perceived interoceptive awareness on the MAIA-2. Sum scores for the VFI-Part1 and VHI-10 were added for each subject and inputted into an Excel spreadsheet. The total sum on the MAIA-2 and items from each subscale on the MAIA-2 were summed, averaged, and inputted into the same Excel spreadsheet. Items 5, 6, 7, 8, and 9 on Non-Distracting and items 11, 12, and 15 on Not-Worrying on the MAIA-2 were reverse-scored (5-x), per the MAIA-2 instructions.²²

Voice disorder diagnoses were based on case history and laryngoscopy, and provided by one of three fellowship-trained laryngologists at the UT Southwestern Center for Voice Care. In addition to data input for the VFI-Part1, VHI-10, and MAIA-2, the patient’s voice disorder type (neurological, structural, functional), demographics (age, gender), and self-reported singing identity (yes/no) were obtained from their initial voice assessment documentation found in their medical chart. Neurological voice disorders included sensorimotor disorders or disorders of the recurrent laryngeal nerve or superior laryngeal nerve (eg, vocal fold paralysis, vocal tremor, and laryngeal dystonias). Structural voice disorders included lesions in the vocal fold mucosa (eg, nodules, polyps, and cysts), sulcus, granulomas, edema, laryngeal cancers, subglottic stenosis, loss of lamina propria (atrophy), and fungal laryngitis. Functional voice disorders included primary muscle tension dysphonia, muscle tension aphonia, and odynophonia.

Statistical analysis

Multivariable linear regression models were used to assess the association between the VFI-Part1 and various patient factors. Predictors included in the models were gender, age at diagnosis, aggregated MAIA-2 sum score, and binary predictors that indicated whether the patient self-identified as a singer and their voice disorder type. Additional regression analyses were run with the aggregated MAIA-2 sum scores replaced by the eight MAIA-2 subscales to understand the effect of different self-perceived interoceptive awareness constructs on VFI-Part1 responses. Power calculations demonstrated an adequate sample size for the regression models (0.2 effect size, 87%, and 73% power when the MAIA-2 sum score and MAIA-2 subscales were used, respectively). Two-tailed tests were conducted with significance levels set at 0.05. All analyses were completed using R version 4.2.0.²³

RESULTS

The effect of voice disorder type (neurological, functional, structural) and psychosocial impact (VHI-10) on VFI-Part1 responses

Of the 95 participants, 37 had a functional voice disorder, 31 had a structural voice disorder, and 27 had a neurological voice disorder. Table 1 shows a breakdown of demographics and patient diagnosis by voice disorder type. Disorder type was included as a three-level factor in the model. There were no significant effects of vocal fatigue among different voice disorder types. Patients with structural voice disorders were expected to score 1.070 points higher on the VFI-Part1 compared to patients with functional voice disorders. Patients with neurological voice disorders were expected to score 1.445 points higher on the VFI-Part1 compared to patients with functional disorders. Patients with neurological voice disorders were expected to score only 0.375 points higher in VFI-Part1 responses compared to patients with structural voice disorders. However, none of these differences between the three group comparisons were statistically significant at the 0.05 significance level, with P-values of 0.533 for the difference between neurological and functional voice disorders, 0.487 for the difference between neurological and functional voice disorders, and 0.859 for the difference between neurological and structural voice disorders. Conversely, we found a significant positive association between VHI-10 ratings and VFI-Part1 responses (P < 0.001), with a one-unit increase in the VHI-10 rating corresponding to an expected 0.91 unit increase in the VFI-Part1 response.

TABLE 1.

Voice Disorder Type by Demographics and Diagnosis

	Neurological (n = 27)	Structural (n = 31)	Functional (n = 37)
Demographics
Age (years)	63.85 (17.20)	42.48 (18.49)	42.76 (16.98)
Gender	59% Women	71% Women	76% Women
	41% Men	29% Men	24% Men
% Self-identified singers	22	68	62
Voice disorder diagnosis*	Vocal fold atrophy (n = 10)	Vocal fold polyp (n = 14)	Primary muscle tension dysphonia (n = 35)
	Vocal fold paralysis (n = 8)	Vocal fold edema (n = 4)
	Vocal tremor (n = 5)	Vocal fold nodules (n = 3)	Odynophonia (n = 2)
	laryngeal dystonia (n = 4)	Vocal fold sulcus (n = 2)	Muscle tension aphonia (n = 2)
		Fungal laryngitis (n = 2)	Irritable larynx syndrome (n = 1)
		Phonotraumatic lesion (n = 2)
		Vocal fold scar (n = 1)
		Laryngeal carcinoma (n = 1)
		Reinke’s edema (n = 1)
		Granuloma (n = 1)
		Vocal fold hemorrhage (n = 1)
		Subglottic stenosis (n = 1)

^*Four subjects with neurological voice disorders, three subjects with structural voice disorders, and three subjects with functional voice disorders had multiple diagnoses within the same category.

The effect of patient demographics (age and gender) on VFI-Part1 responses in patients with voice disorders

Of the 95 participants with voice disorders, 66 identified as women and 29 identified as men. Mean age was 48.66 (SD: 19.74, range: 16–91). Age did not have a significant effect on the VFI-Part1 in patients with voice disorders (P = 0.220). Gender also did not have a significant effect on the VFI-Part1 in patients with voice disorders (P = 0.431).

The effect of singing experience and interoceptive awareness (MAIA-2) on VFI-Part1 responses in patients with voice disorders

Fifty-three percent (52.63%) of the patients self-identified as singers. The singing experience did not have a significant effect on VFI-Part1 responses (P = 0.360). Although there was a trend toward significance, there was no significant relationship between the MAIA-2 sum scores and responses on the VFI-Part1 (P = 0.056). There were also no significant relationships between the VFI-Part1 and MAIA-2 sub-scores: Noticing (P = 0.384), Non-distracting (P = 0.900), Not worrying (P = 0.630), Attention Regulation (P = 0.286), Emotional Awareness (P = 0.453), Self-Regulation (P = 0.338), Body Listening (P = 0.561), and Trusting (P = 0.176).

DISCUSSION

The objectives of this study were to determine the effects of psychosocial impact and patient profiles such as voice disorder type, demographics (age and gender), singing identity, and interoceptive awareness on self-perceived measures of vocal fatigue using the VFI-Part1 in patients with voice disorders. There were several patterns identified from these results. First, there were significant relationships between vocal fatigue and psychosocial impact as measured on the VHI-10. Results from this study parallel previous work demonstrating a strong correlation between the VFI and self-perceived severity of voice impact, including the VHI²⁴ and the Voice Related Quality of Life Index,²⁵ in participants with and without voice complaints.

Second, there were no significant relationships between voice disorder type, age, gender, singing experience, or level of self-perceived interoceptive awareness when compared to self-perceived vocal fatigue severity. Interestingly, although there were no significant differences in vocal fatigue severity across voice disorder types (neurological, structural, and functional), the results suggest patients with neurological and structural voice disorders tended to report slightly higher levels of vocal fatigue compared to those with functional voice disorders. Previous work found patients with primary muscle tension dysphonia had significantly greater vocal effort and vocal fatigue levels compared to vocally healthy voice users,^4,26 but to our knowledge, there have been no studies comparing vocal fatigue severity across different types of voice disorders. The lack of significant relationships between voice disorder types suggests patients with different types of voice disorders do not differ significantly in their self-perceived levels of vocal fatigue, regardless of the pathophysiological mechanisms underlying clinical presentations of vocal fatigue severity levels.

Third, age and gender also did not have significant relationships to vocal fatigue severity. This study parallels previous work that found no significant relationships between age on any of the three VFI factors.¹¹ Although previous literature suggests there may be a higher prevalence of voice disorders in women and that women may report more vocal health problems than men, study outcomes on the topic of gender and vocal fatigue have remained inconclusive within and across studies. Furthermore, the majority of these studies have omitted patients with voice disorders in their experimental designs,^12–14 making it challenging to deduce whether vocal fatigue is more prevalent in women with voice disorders.

In one study, although 38% of women self-reported a voice problem compared to 26% of men and there was a higher prevalence of women reporting vocal fatigue compared to men, results were not statistically significant.¹³ There were also no relationships between gender and level of vocal fatigue on the impact of teaching activities in this study.¹³ Another study found that although women reported greater psychological distress, gender did not seem to influence physical symptoms in health reporting.²⁷ These findings could explain the lack of gender differences in vocal fatigue symptom reporting by the patients with voice disorders in this study—especially in the context of Part 1, which measures physical tiredness associated with vocal fatigue and voice avoidance symptoms.²⁰

Fourth, the lack of significant findings on self-perceived interoceptive awareness measures is both intriguing and informative in the context of symptom reporting. Previous work found that patients with functional voice and upper airway disorders who reported higher symptom ratings on the VHI-10 and VFI-Part1 had significantly lower Attention Regulation ratings on the MAIA-2 sub-scale.¹⁹ Patients with primary muscle tension dysphonia also had significantly lower scores on the Emotional Awareness MAIA-2 sub-scale compared to typical voice users in this study.¹⁹ These findings suggest patients with functional voice and upper airway disorders who score higher on the VHI-10 and who also score higher on the VFI-Part1 may have lower capabilities to attend to body sensations. Patients with primary muscle tension dysphonia, a type of functional voice disorder, may also have more difficulties processing body sensations, at least compared to typical voice users. Although we did see significant relationships between VHI-10 and VFI-Part1 reporting in this study, which parallels this previous work, there were no significant differences in interoceptive awareness levels across patients with different types of voice disorders as it relates to vocal fatigue found in this study. This study also parallels previous work that did not find significant relationships between singing experience and interoceptive awareness in subjects with and without voice disorders.¹⁹

Summary of the impact of patient profiling in voice patients with vocal fatigue

Taken together, these findings suggest that although vocal fatigue has a significant psychosocial impact, caution should be exercised when attributing demographics (eg, gender), health status (eg, voice disorder type), or identity (eg, singer), to clinical presentations of vocal fatigue in patients with voice disorders. Although patient profiling can provide cognitive shortcuts in how we diagnose and determine the prognosis of a voice disorder, when we see patients as a collection of risk factors based on who they are as individuals, their appearance, identity, or health status, we run the risk of extrapolating information about a person based on perceived traits or tendencies. The act of patient profiling can result in biased assumptions about our patients and may even lead to presumptions, fractured patient-provider relationships, and inequitable care. Those who are professional providers to patients with various voice disorders should be responsive and sensitive to patient reporting. Furthermore, highlighting the relationship between psychosocial impact and vocal fatigue calls for voice professionals to employ interventions that tackle these psychosocial elements in an effort to take a holistic approach to patient-centered care.

Limitations

Measuring vocal fatigue using the VFI does have some inherent limitations. The first is that the VFI is just a snapshot of a patient’s daily experiences at that moment. How patients respond to questions on the VFI may depend on varying factors such as current mood, time of day, or the types of vocal demands the patient experienced prior to their clinical appointment. The second is that the VFI instructions ask the patient to rate the frequency of their vocal fatigue symptoms but do not provide a set time point for reference. As such, patients may complete the VFI based on their vocal fatigue experience at that moment, during that day, within the past week or month, or indefinitely. These factors should be taken into account in the future when assessing severity levels of vocal fatigue in patients with voice disorders.

Future directions

While the specific patient factors that were investigated in this study did not play a significant role in vocal fatigue symptom reporting, it is important to note that other factors that were not explored in this study could play a role. Future studies investigating relationships between vocal fatigue perceptions, different types of occupational demands, or other psychosocial influences like emotional or physical trauma in patients with voice disorders, could provide novel insights into ways in which other psychosocial and occupational factors influence how patients perceive their vocal fatigue. Additionally, future studies investigating the role of mindfulness, meditation, or psychotherapy alongside traditional voice therapy, may help us provide more specialized treatment approaches for patients with vocal fatigue.

CONCLUSION

Vocal fatigue has a significant psychosocial impact on patients with voice disorders. However, disorder type, patient age, gender, singing identity, and level of interoceptive awareness do not appear to play a major role in vocal fatigue symptom reporting across patients with different types of voice disorders. These findings suggest other, likely biophysiological mechanisms, underlie symptoms of vocal fatigue beyond the patient’s clinical profile.