Teachers’ Voice Disorders and Loss of Work Ability: A Case-Control Study rio Dias de Oliveira Latorre, kFrida Marina Fischer, *,†,‡Susana Pimentel Pinto Giannini, §Maria do Rosa  {Ana Carolina de Assis Moura Ghirardi, and #Leslie Piccolotto Ferreira, *yzxk{# S~ao Paulo, Brazil Summary: Background. Teachers constitute a profession with a high occurrence of voice disorders due to the occupation’s intense vocal demands and unfavorable work environment. Purpose. To identify the association between voice disorders and work ability among teachers from public schools in S~ao Paulo, Brazil. Methods. This is a case-control study. The case group comprised teachers with voice disorder complaints, vocal quality deviations in speech pathology evaluations, and vocal fold lesions according to an evaluation by an otorhinolaryngologist. The control group was randomly selected from the same schools as those in the case group. Both groups answered the following questionnaires: sociodemographic, lifestyles, working conditions, work organization, conditions of vocal production—teacher (CVP-T), and Work Ability Index (WAI). The analysis used the chi-square association test and univariate and multivariate regression models. Results. The analyses of both groups showed comparable populations with no significant differences in the demographic and control variables. The groups differed, as expected, in vocal symptoms. Analyzing associations with the WAI, there was an association between decreased work ability and voice disorder (P < 0.001). This association remained in multivariate analyses where decreased (OR ¼ 9.5, P ¼ 0.001) and moderate (OR ¼ 6.7, P < 0.001) work ability were also associated with voice disorders. Analyzing the ability to work, age, and acoustics; decreased (OR ¼ 12.2, P < 0.001) and moderate (OR ¼ 7.7, P < 0.001) work ability, age 50–65 years (OR ¼ 3.7, P ¼ 0.006) and poor acoustics (OR ¼ 2.7, P ¼ 0.007) were factors associated with voice disorders. Conclusions. The occurrence of voice disorders is significantly associated with work ability, which may eventually compromise teachers’ ability to continue working. Key Words: Occupational health–Voice disorders–Work ability index evaluation–Teachers. INTRODUCTION Teachers occupy a privileged position in society, playing an important role in human development and the educational process. However, this occupation has been undergoing a loss of prestige over the past years and as a result there is a growing association between teaching and various illnesses. Mental and vocal disorders are the main causes of temporary absences or permanently leaving work.1–3 Teachers report multiple symptoms that negatively affect their performance during teaching activities and voice disorders are a source of stress and frustration.4 The social importance of withdrawal from work is not restricted to the economic aspects, which are not to be ignored, but being removed from teaching activities leads to faculty members feeling insecure and isolated.5 When the teacher loses his or her voice, he or she is unable to perform

Accepted for publication June 5, 2014. This study was presented at the 18th Brazilian Speech-Language Pathology and Audiology Congress (September 22–25, 2010, in Curitiba, Parana, Brazil) (http://www.sbfa. org.br/fono2010/pdf/trabahospremiadoscongresso2010.pdf). From the *Public Health—Epidemiology at the School of Public Health, University of S~ao Paulo (FSP-USP), S~ao Paulo, Brazil; yCity Public Health Care System, Brazil; zEducation and Rehabilitation Division of Communication Disorders (DERDIC-PUCSP), S~ao Paulo, Brazil; xDepartment of Environmental Health, School of Public Health, University of S~ao Paulo (FSP-USP), S~ao Paulo, Brazil; kSchool of Public Health, Department of Epidemiology, University of S~ao Paulo (FSP-USP), S~ao Paulo, Brazil; {Program in Speech-Language Pathology, Pontifical Catholic University of S~ao Paulo, S~ao Paulo, Brazil; and the #Program in Speech-Language Pathology and Audiology, Pontifical Catholic University of Sao Paulo (PUC-SP), S~ao Paulo, Brazil. Address correspondence and reprint requests to Susana Pimentel Pinto Giannini, Avenida Nhandu, 334—Planalto Paulista, CEP 04059-000, S~ao Paulo, Brazil. E-mail: [email protected] Journal of Voice, Vol. -, No. -, pp. 1-9 0892-1997/$36.00 Ó 2014 The Voice Foundation http://dx.doi.org/10.1016/j.jvoice.2014.06.004

routine classroom functions, and loses his or her professional identity. Personal characteristics like excessive speaking or yelling and biological aspects like allergies or pharyngeal/laryngeal reflux, in addition to the inappropriate environmental characteristics of schools, are factors associated with voice disorders. On the other hand, aspects that originate in various patterns of work organization also play a preponderant role in determining teachers’ vocal illnesses.6,7 The decrease in work ability is the result of a process that involves multiple variables including sociodemographic aspects, lifestyles, mental resources, chronological age, work requirements, and health status, which are the main determinants.8,9 Voice disorders make teaching difficult or impossible, and characterize an inability to work as a teacher. This case-control study aims to advance the identification of factors related to teachers’ working conditions and work organizational aspects associated with work ability. The purpose of this study is to determine the association between voice disorders and loss of work ability among female teachers at public schools in S~ao Paulo. METHODS Study design This was a case-control study with cases and controls paired by school to control for exposure to physical, chemical, and biological environmental aspects. Sampling The study was conducted with female preschool, elementary, middle, and high school teachers working in the public school

2 system of S~ao Paulo (Brazil). Teachers with organic vocal fold disorders and those who were not actively performing classroom functions for medical reasons or who were performing administrative work at the time of data collection were excluded from the sample. Teachers who might have previously received guidance or treatment were not excluded because there is a current Vocal Health Program run by the city’s medical administration office. To determine the sample size, a type I error of 5% was assumed, and test power of 80%, maximum exposure frequency among the controls of 40%, and minimum odds ratio (OR) value of 2.5. Based on these assumptions, we estimated that 85 cases and 85 control subjects would be needed for the study. Definition of cases and controls The main methodological difficulty in this study was the definition of cases, because the dependent variable ‘‘voice disorder’’ is a dynamic and functional manifestation. Thus, it is quite difficult to create dichotomist definitions of illness and absence of illness. The definition of cases is crucial in case-control studies and, where voice disorders are concerned, it is difficult to define the illness (case) in opposition to the absence of any sign or symptom. This definition is found in different forms and classifications in the literature. Most studies rely solely on the presence of voice symptoms when considering the presence or absence of the disorder.10 However, such manifestations are not specific enough to distinguish healthy and unhealthy individuals. A number of authors11–13 have stated that the presence of symptoms and a professional evaluation, especially a laryngeal evaluation,5 should be included. However, there is presently no consensus on which evaluation procedure should be the gold standard to clearly define a case of voice disorder. In the present study, the case definition was based on the results of both vocal and laryngoscopic assessments. Considering the aspects regarding these evaluations, the case definition could have been done in three different ways: (1) teachers with disorders in the perceptive-auditory voice evaluation and without the disorder in the perceptive visual otolaryngology evaluation. In this situation, two possibilities may be considered: the existence of minimal structural disorders in the vocal folds that could not be seen during laryngoscopy, or an initial vocal manifestation without a corresponding organic sign; (2) subjects without a disorder in the perceptive-auditory vocal evaluation and a disorder in the perceptive visual evaluation. Even teachers who have a slight or moderate disorder on the medical examination who have a well-adapted voice could fit this category; (3) subjects with disorders in both perceptive-auditory and perceptive visual assessments. Although situations (1) and (2) could be considered cases of voice disorders from a clinical standpoint, the option in this study was to consider as cases only those teachers classified as (3); that is, those with a consensus between the voice and laryngeal evaluations, whereas those classified in the other categories were excluded from the analysis. The teachers considered cases were those with alteration in their vocal evaluations (GRBASI scale 2 or 3) and the presence of a lesion or irritative and/or structural disorder or chinks in the vocal folds during an ear, nose, and throat (ENT) perceptive and visual assessment. The control group comprised subjects with

Journal of Voice, Vol. -, No. -, 2014

an absence of or mild vocal quality alterations in the perceptive-auditory assessment (GRBASI scale 0 or 1) and those with no observed alterations in the ENT assessment. Teachers who had disorders in only one of the two different assessments were removed from the study to obtain groups that were clearly distinct categorized by the illness focused on in this study. Instruments Two questionnaires were used: (1) the conditions of vocal production of teachers (CPV-P) instrument, which has been used in different studies in Brazil, can adequately characterize the conditions of school environments and the vocal profile of teachers. In this study, the answers provided sociodemographic, lifestyle, occupational, environmental, and school-work organization data.14,15 In the present study, the answers were given on a Likert scale (never, seldom, sometimes, always, and I don’t know) and provided data regarding the variables of sociodemographics, lifestyles, and occupational and work environment and organization. These variables were analyzed in two categories: no (never, seldom, I don’t know) and yes (sometimes, always). The answers to the question ‘‘what symptoms do you currently experience?’’ were the basis for determining the number and frequency of vocal symptoms. Likewise, subjects were deemed to be without symptoms (never, seldom, I don’t know) or with symptoms (sometimes, always). (2) The Work Ability Index (WAI) assesses a person’s work ability to suggest intervention measures and health promotions to prevent further losses and to maintain the person’s current work ability.16 The WAI originated from occupational health studies in Finland.17 The questionnaire may be completed from the time the subject enters the workforce to determine a reliable prognosis of changes in work ability of different professional groups. The WAI’s contribution in the study of work ability is owed to its predictive value for disability, health/illness, and death rate.18 The assessment considers the physical and mental requirements of the work, the worker’s health conditions, and his/her mental and physical resources.8 It has been translated and validated by researchers from the Public Health School of the University of S~ao Paulo and other Brazilian institutions.19 The WAI may detect early disorders associated with work ability and may be used to predict the risk of disability in the near future independently of age. It is composed of seven dimensions: current work ability compared with the best in life, work ability in relation to work demands, current number of illnesses diagnosed by a doctor from a list of 51 illnesses, estimated loss of work because of illnesses, and work absences because of illnesses. The score is calculated as the sum of points scored for each of the seven dimensions, and varies between 7 and 49, where 7–27 corresponds to low ability, 28–36 to moderate ability, 37–43 to good ability, and 44–49 to excellent work ability.17 Data collection The selection of participants took place in two phases. The participants in the first phase were all teachers attending the

Susana Pimentel Pinto Giannini, et al

Voice Disorders and Work Ability Among Teachers

Speech-Language Pathology service of the Public City Worker’s Hospital with vocal complaints between July 2007 and May 2009, and who underwent vocal and laryngoscopic assessments. In the second phase, researchers went to the schools where the case teachers worked and randomly selected teachers from the same schools for the control group. All selected teachers were subjected to the same procedures previously mentioned. Teachers who had a voice disorder were placed in the case group, and those classified as without a voice disorder were assigned to the control group. Speech examinations were performed by speech-language pathologists on the same day of the week (Friday mornings) so that a minimum of 12 hours of vocal rest was assured. Data were registered directly in a portable computer using a headset microphone. The option of conducting a perceptiveauditory analysis was given because this is the standard procedure in vocal assessments, and for using the GRBASI scale,20,21 an instrument that is widely used internationally and that has high agreement rates. Vocal evaluation was performed simultaneously using three speech-language pathologists experienced in the field. The pathologists had no knowledge of the subjects’ identities. Each voice was classified as altered (moderate or intense alteration, grades 2 or 3) or not altered (normal or mild, grades 0 or 1). All otorhinolaryngologic evaluations were performed by the same ENT doctor, experienced in laryngology on Fridays after voice sample collections. A video laryngoscopy was performed with both rigid and flexible laryngoscopes under local anesthesia (lidocaine spray) when needed. The assessment protocol included general ENT and specific laryngeal aspects. Subjects were classified as altered when lesions, irritative structural disorders, or chinks in the vocal folds were detected, or not altered in the absence of any lesions or disorders. The perceptual auditory voice assessment, which was performed by a speech-language pathologist, and the perceptive visual evaluation, which was performed by the ENT doctor, had a good agreement level (76.9%, P ¼ 0.525). Variables The dependent variable was the presence of voice disorder (yes ¼ case; no ¼ control), and the independent variable of interest was work ability (low, moderate, good, and excellent). Independent control variables included characteristics regarding sociodemographics (age, marital status, and education level); lifestyle (alcohol consumption and smoking), teaching (time in profession, type of work contract, number of teaching hours per week), environment (noise, echo, dust, humidity, classroom temperature, acoustics; classroom size and lighting, school cleanliness, use of harmful cleaning chemical products), and work organizational factors (quietness, presence of constant supervision, stressful work pace, time to accomplish all tasks at school, rest area, job satisfaction, school maintenance, monotonous work, repetitive work, stress and violence at work and how often, abuse of school property, theft of personal items, threats toward teachers, need for police intervention, racism, lack of discipline, fights, aggressions, insults, violence, drug issues, and graffiti).


Statistical analyses The WAI’s internal consistency was assessed by calculating Cronbach alpha coefficient. A descriptive analysis and a study of the association with the variable of interest to compare the case and control groups were conducted (chi-square association test with Yates correction coefficient). Logistic regression models were estimated to calculate the crude and adjusted OR to assess the risks in relation to the independent variable of interest. For multivariate analysis, independent control variables were selected with significance levels less than 0.10 (P < 0.10) in univariate analyses. The variables that remained significant after adjustment for the other variables were kept in the model. Evaluation of the adjustment of the final multiple models was done using the Hosmer-Lemeshow test. Ethical guidelines The study was approved by the Research Ethics Committees of the School of Public Health of the University of S~ao Paulo (protocol n 173/07) and the Public Servant Municipal Hospital (protocol n 101/07). All subjects were informed and voluntarily agreed to participate in the study by signing a free consent form. This study was funded by the Research Support Foundation of the State of S~ao Paulo (Fundac¸~ao de Amparo a Pesquisa do Estado de S~ao Paulo—FAPESP). RESULTS In total, 354 assessments were conducted. At the end of this process, the case group comprised 167 teachers, and the control group comprised 105 teachers. The group analysis showed that the samples were comparable because there was no difference between groups with regards to sociodemographic, lifestyle, and occupational characteristics as shown in Table 1. Age was identified as an independent control variable (P < 0.10) in the logistic regression analysis. There was also no difference between the case and control groups in the characterization of perceived work environment conditions (Table 2) and work organization (Table 3), which was expected because participants in both groups were paired by their work places. The only variable that showed a difference was acoustics, which was also added to the logistic regression analysis for adjustment. Regarding vocal and nonvocal symptoms, the groups were differentiated because all of the evaluated symptoms were associated as shown in Table 4. It should be noted that although symptoms such as hoarseness, tiredness while speaking, or strained speech may be associated with the case group, these manifestations were not proven to be specific enough to distinguish, in isolation, individuals who do and do not have a voice disorder. This was confirmed by observing that 51% (n ¼ 52) of the subjects in the control group reported hoarseness, 50% (n ¼ 51) tiredness when speaking, and 52.4% (n ¼ 54) strained speech. The WAI general score had a Cronbach alpha coefficient of 0.75 showing good reliability for the instrument in this study. An association was observed between work ability reduction


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TABLE 1. Distribution of Cases and Controls, According to Sociodemographic and Lifestyle Characteristics Controls (n ¼ 105) Sociodemographic Characteristics Age 20–29 years 30–39 years 40–49 years 50–65 years Married status Single Married Separated/widow Education Up to incomplete college degree College degree and over Working time as a teacher  10 y 11–15 y 16–20 y  21 y Contract Main teacher Substitute teacher Weekly working hours  10 11–20 21–30 31–40  41 Smoking habits Non-smoker Ex-smoker Smoker Alcohol consumption Never Seldom Sometimes


15 38 33 19

Cases (n ¼ 167) 


P Value (c2)

14.3 36.2 31.4 18.1

21 50 77 19

12.6 29.9 46.1 11.4


27 62 16

25.7 59.0 15.2

49 100 18

29.3 59.9 10.8


4 101

3.8 96.2

13 154

7.8 92.2


33 23 29 19

31.7 22.1 27.9 18.3

40 29 62 36

24 17.4 37.1 21.5


101 4

96.2 3.8

158 9

94.6 5.4


14 16 32 24 19

13.3 15.2 30.5 22.9 18.1

29 22 31 48 37

17.4 13.2 18.6 28.7 22.2


84 11 10

74.1 10.5 9.5

132 16 19

79.0 9.6 11.4


45 43 16

43.3 41.3 15.4

78 60 29

46.7 35.9 17.4



and voice disorder (P < 0.001). In the control group, 66.6% (n ¼ 58) of subjects considered their work ability good or excellent, whereas 67.4% (n ¼ 99) of subjects in the case group considered their work ability either poor or moderate. Two multivariate analysis models of the variable of interest and the presence of a voice disorder were studied, with the results shown in Table 5. Model 1 shows the univariate analysis of voice disorder and the WAI categories. Low and moderate work ability was associated with having a voice disorder. Model 2 looked at the association between voice disorder and the WAI after adjusting for the control variables that met the P < 0.10 requirement in the chi-square association test (age and acoustics). The categories of poor and moderate work abilities remain significant independently of the age group and the presence of unfavorable acoustics in the school. These were also independent factors associated with voice disorders.


DISCUSSION This paired case-control study assessed the association between having a voice disorder and loss of work ability among female teachers working at public schools in S~ao Paulo. The case and control groups were similar with regard to practically all sociodemographic, lifestyle, occupation, work environment, and organization factors. Regarding vocal aspects, all vocal symptoms evaluated were associated with the presence of a voice disorder, which confirms that the groups were differentiated specifically by the presence of a voice disorder. It should be noted that although symptoms such as hoarseness, tiredness when speaking, and strained speech were associated with the case group, these manifestations were not specific enough to distinguish between those with or without a voice disorder. The only environmental exposure variable associated with voice disorder was acoustics (P ¼ 0.010). When selected in multivariate analyses, acoustics remained significant in the

Susana Pimentel Pinto Giannini, et al


Voice Disorders and Work Ability Among Teachers

TABLE 2. Distribution of Cases and Controls, According to Physical Work Environment Characteristics Controls (n ¼ 105) Physical Work Environment Aspects Presence of disturbing noise No Yes Unfavorable acoustics No Yes Presence of echos No Yes Dusty environment No Yes Humidity No Yes Pleasant classroom temperature No Yes Adequate classroom size No Yes Adequate lighting No Yes Satisfactory cleanliness No Yes Satisfactory cleanliness in restrooms No Yes Irritative cleaning products No Yes

Cases (n ¼ 167) 




P Value (c2)

3 99

2.9 97.1

4 162

2.4 97.6


20 85

19.0 81.0

55 109

33.5 66.5


19 85

18.3 81.7

35 129

21.3 78.7


10 94

9.6 90.4

1 155

7.2 92.8


24 78

23.5 76.5

39 123

24.1 75.9


22 80

21.6 78.4

41 125

24.7 75.3


53 51

51.0 49.0

91 76

54.5 45.5


7 98

6.7 93.3

9 94.6

16 89

15.2 84.8

21 146

12.6 87.4


6 99

5.7 94.3

20 147

12.0 88.0


24 81

22.9 77.1

31 135

18.7 81.3



multiple regression model and was independent of age and work ability. Unfavorable acoustics at school is one of the main environmental factors associated with teachers’ voice disorders.10,22,23 Background noise during teaching activities was reported by 75% of teachers, and elevated and unbearable noise perception in the classroom and school is strongly associated with and has a positive intensity gradient with the presence of mental disorders.7 Regarding sociodemographic aspects, the variable ‘‘age’’ met the P < 0.010 requirement and was further tested in multiple regression models as an adjustment variable. The 50–65 year age bracket was associated with having a voice disorder independent of work ability. There is no consensus regarding when the process of vocal aging begins, but the voice undergoes changes with age,24 with a greater chance of having a vocal disorder increasing with the teacher’s age.1 Likewise, duration of exposure time to teaching functions is associated with a greater frequency of negative, acute, or

9 158


chronic effects on the voice.25 Teachers with five or more years of work experience have a 35% greater chance of having dysphonia than those with less years of experience in the occupation.26 Previous studies also showed that the voice disorder favors a change in occupation or untimely removal from classroom functions.27 The present study verified an association between reduced work ability and having a voice disorder. In the association analysis conducted with all the independent variables of interest, poor and moderate work ability were statistically associated with having a voice disorder, regardless of age and acoustics (Table 5, Model two). In all WAI analyses, the presence of a dose-response is observed; that is, the longer the exposure, the greater the chance of having the outcome and the greater the observed outcome (Table 5). This is one of the strongest indicators of a causal relationship. The concept of work ability is anchored in the interaction between work demands and the worker’s physical and mental resources, representing a measurement of functional aging.8 In


Journal of Voice, Vol. -, No. -, 2014

TABLE 3. Distribution of Cases and Controls, According to Work Organization Characteristics Controls (n ¼ 105) Aspects of Work Organization


Calm environment No 37 Yes 67 Constant supervision No 11 Yes 90 Stressful work pace No 1 Yes 104 Enough time to accomplish work activities No 19 Yes 86 Able to leave the classroom No 32 Yes 73 Satisfaction with position No 4 Yes 101 Monotonous work No 26 Yes 69 Repetitive work No 19 Yes 84 Violence at work School property abuse No 23 Yes 81 Theft of personal belongings No 36 Yes 68 Threats to the teacher No 28 Yes 76 Racist manifestations No 31 Yes 72 Lack of discipline No 7 Yes 98 Fights No 18 Yes 87 Violence against employees No 34 Yes 71 Drug abuse issues No 29 Yes 76

this study, the WAI proved to be a marker strongly associated with having a voice disorder. It also illustrates the repercussions of vocal illnesses on teachers’ lives and careers. The results point toward early functional aging in teachers with voice disorders, regardless of the decline associated with

Cases (n ¼ 167) 




P Value (c2)

35.6 64.4

60 100

37.5 62.5


13.2 89.1

22 145

13.2 86.8


1.0 99.0

2 163

1.2 98.8


18.1 81.9

37 127

22.6 77.4


30.5 69.5

68 41

41.0 59.0


3.8 96.2

6 160

3.6 96.4


27.4 72.6

41 117

25.9 74.1


18.4 81.6

32 132

19.5 80.5


22.1 77.9

42 124

25.3 74.7


34.6 65.4

60 107

35.9 64.1


26.9 73.1

51 116

30.5 69.5


30.1 69.9

56 111

33.5 66.5


6.7 93.3

10 156

6.0 94.0


17.1 82.9

28 137

17.0 83.0


32.4 67.6

52 114

31.3 68.7


27.6 72.4

38 129

22.8 77.2


age. Aspects referring to health are determinants of work ability and, in this case, the vocal symptoms play a pivotal role. Educators essentially depend on their voices for their ability to work, and the development of a voice disorder leads to self-distancing from the active work of teaching.

Susana Pimentel Pinto Giannini, et al


Voice Disorders and Work Ability Among Teachers

TABLE 4. Distribution of Cases and Controls, According to Vocal Symptoms Controls (n ¼ 105) Vocal and Nonvocal Symptoms Hoarseness No Yes Voice loss No Yes Shortage of breath when speaking No Yes Pain when speaking No Yes Tiredness when speaking No Yes Strained speech No Yes Dry throat No Yes Stingy throat No Yes Phlegm No Yes

Cases (n ¼ 167)





P Value (c2)

50 52

49.0 51.0

11 156

6.6 93.4

Teachers' voice disorders and loss of work ability: a case-control study.

Teachers constitute a profession with a high occurrence of voice disorders due to the occupation's intense vocal demands and unfavorable work environm...
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