Hoarseness and vocal tract discomfort and associated risk factors in air traffic controllers

Introduction An air traffic controller is a professional who performs air traffic control functions in air traffic control units and is responsible for controlling the various stages of a flight. Objective To compare hoarseness and vocal tract discomfort and their risk factors among air traffic controllers in the approach control of São Paulo. Methods In a cross-sectional survey, a voice self-evaluation adapted from to self-evaluation prepared by the Brazilian Ministry of Labor for teachers was administered to 76 air traffic controllers at approach control of São Paulo, Brazil. Results The percentage of hoarseness and vocal tract discomfort was 19.7% and 38.2%, respectively. In relation to air pollution, the percentages of hoarseness and vocal tract discomfort were higher among those who consider their working environment to be intolerable than among those in a comfortable or disturbing environment. The percentage of hoarseness was higher among those who seek medical advice due to vocal complaints and among those who experience difficulty using their voice at work than among those who experience mild or no difficulty. The percentage of vocal tract discomfort was higher among those in a very tense and stressful environment than among those who consider their work environment to be mild or moderately tense and stressful. The percentage of vocal tract discomfort was higher among those who describe themselves as very tense and stressed or tense and stressed than among those who describe themselves as calm. Additionally, the percentage of vocal tract discomfort was higher among those who care about their health. Conclusion Among air traffic controllers, the percentage of vocal tract discomfort was almost twice that of hoarseness. Both symptoms are prevalent among air traffic controllers who considered their workplace intolerable in terms of air pollution. Vocal tract discomfort was related to a tense and stressful environment, and hoarseness was related to difficulty using the voice at work.


Introduction
Professional voice use is defined as oral communication by people who depend on their voice to perform their working activities. 1 Approximately one-third of current professions use the voice to varying degrees. 2 Among professionals who rely on their voices, teachers are the focus of most studies on professional voice use. 3---10 As another professional voice user, Air Traffic Controllers (ATCs) have been the focus of few studies on voice problems and communicative competence. 11 An ATC is a professional who performs air traffic control functions in air traffic control units under the Brazilian Aeronautics Command. These professionals are responsible for controlling the various stages of a flight. 12 An aircraft normally passes through three levels of traffic control between takeoff and landing. The tower is responsible for the aircraft until it loses visual contact with the aircraft, while the Approach Control (APP) and the Area Control Center (ACC) are both responsible for the direction of the plane in the air. 11 The function of APP controllers is to ensure a minimum distance between planes under their command near the airport and to indicate by radio the coordinates (headings), speeds, and altitudes that the pilot must adopt to fly with maximum safety and avoid collisions. 12 This is a highly dynamic task that requires the special attention of these controllers because in addition to providing the final sequence for landing, ATCs must separate the aircraft that are landing from those that are taking off. Their voice is therefore of the utmost importance, and any vocal alterations that influence the transmission of their voice to pilots, even if temporary, may put hundreds of lives at risk. 11 The São Paulo Approach Control (APP-SP) is responsible for an area of approximately 260 km and responsible for the movement of 320,179 aircraft in 2015, which represents 17.6% of the annual aircraft movement at airports administered by the Brazilian Company of Airport Infrastructure. 13 The ATCs who work at this control area therefore tend to be at a higher risk for dysphonia because in addition to the natural stress of their work, they are subject to greater demands being placed on their voices than those experienced by ATCs from other operating bodies. 11 We recently used a voice self-evaluation survey, designed by the Brazilian Ministry of Labor for teachers, 14 to obtain an epidemiological profile of voice complaints (hoarseness and vocal tract discomfort) and risk factors in university teachers. 6---8 University teachers show a high percentage of hoarseness and vocal tract discomfort (39.6% and 50.8%, respectively). Factors such as time of teaching, gender, work organization, workplace conditions, as well as personal habits and style/quality of life are related to these self-related symptoms. 7,8 In another recent study on the APP-SP, Villar et al. 11 used a perceptual-auditory analysis of the /a/ vowel and observed that a high percentage of ATCs exhibited vocal alterations (44%), even among a group of subjects without vocal complaints.
We did not find any study about a self-evaluation survey in CTA. The use of this voice self-evaluation adapted to ATCs could provide information about the prevalence of hoarseness and vocal tract discomfort and related risk factors in this important group of professional voice users.
The aim of this study is to compare the self perceived hoarseness and vocal tract discomfort and risk factors in ATC in the APP-SP.

Methods
This cross-sectional study was reviewed by the Ethics Committee in Research of the Federal University of São Paulo (CAAE 49357115.6.0000.5505) and was authorized by the Brazilian Aeronautics Command, from which the data were collected.
Voice self-evaluation forms, which were prepared by the Brazilian Ministry of Labor for teachers, 14 and adapted to ATC, were completed by all 76 ATCs belonging to the APP-SP during a 1 month period in 2016.
The analyzed variables related to hoarseness and vocal tract discomfort were selected from the self-evaluation forms and grouped as follows: Identification variables ---age, gender, and time of work as an ATC (in years); Work organization variables ---professional activities other than ATC and professional activity that consumes the most time.
Workplace variables ---noise, air pollution, air conditioning (the ATC chose between three options: comfortable, tolerable, and intolerable); and stress and anxiety due to the activity (three options: mild, moderate and very tense and stressful).
Voice care variables ---care or medication for the throat or voice, seeking medical advice because of vocal symptoms, and the degree of difficulty of using the voice during work (none, mild, moderate, and severe).
Habits and style/quality of life outside the APP variables ---use of voice, stress and anxiety (calm, tense and anxious, and very tense and anxious), drinking water/hydration, diet, smoking, alcohol consumption, coffee consumption, and health care (absent-minded, controlled/cautious, or concerned).
Differences in hoarseness and vocal tract discomfort rates for each variable were considered. Statistical analyses were performed using the SPSS statistical package for Windows, version 13.0. Student's t-test was used to compare hoarseness and vocal tract discomfort rates with the numerical variables; the chi-square test was used to compare hoarseness and vocal tract discomfort with the categorical variables; and the Fisher's exact or likelihood ratio test was used when necessary. A significance level of 5% (p < 0.05) was used.

Results
The incidence of hoarseness and vocal tract discomfort in the sample of 76 ATCs was 19.7% and 38.2%, respectively. In total, 13.16% of ATCs presented both symptoms. The average and standard deviation time of those working as an ATC was 7.8 ± 6.6 years (between 1 and 37 years). The ATCs were 29.2 ± 6.5 years old and predominantly male (57.9%).

Identification and work organization variables
No statistically significant differences were observed in the rate of hoarseness and vocal tract discomfort for identification and work organization variables (Tables 1 and 2, respectively).

Workplace variables
In terms of air pollution, the percentage of vocal tract discomfort was higher among those who consider workplace intolerable than among those who considered their workplace comfortable and tolerable.
The percentage of vocal tract discomfort was also higher among those who considered their workplace to be a very tense and stressful environment than among those who considered their workplace to be a mild or moderately tense and stressful environment.
No statistically significant differences were observed in the rate of hoarseness and vocal tract discomfort for the other variables (Table 3).

Voice care variables
The percentage of hoarseness was higher among those who had sought medical advice because of hoarseness. The percentage of hoarseness was also higher among those who experienced moderate difficulty working because of vocal problems.
No statistically significant differences were observed in the rate of hoarseness and vocal tract discomfort for the other variables (Table 4).

Habits and style/quality of life variables
The percentage of vocal tract discomfort was higher among those who were stressed and anxious or very tense and anxious than among those who were calm. Moreover, the percentage of vocal tract discomfort was higher among those who were worried about health care.
No statistically significant differences were observed in the rate of hoarseness and vocal tract discomfort for the other variables (Table 5).

Discussion
In their systematic review, Cantor Cutiva et al. 15 found wide variation in the prevalence of voice disorders and suggested that this variation may be due to the use of generic terms such as 'vocal complaints' and 'vocal symptoms' to describe these disorders. Thus, we were interested in using the voice self-assessment survey reformulated by the Ministry of Labor of Brazil, which examines symptoms such as hoarseness and vocal tract discomfort, to obtain an epidemiological profile of vocal complaints and risk factors in an ATC setting. In the present study, the incidence of vocal tract discomfort was almost twice that of hoarseness, at 38.2% and 19.7%, respectively.
Compared to university teachers using almost the same voice self-evaluation, in ATCs the prevalence of hoarseness  and vocal tract discomfort was lower (19.7% vs. 39.6% and 38.2% vs. 50.8%, respectively). 6,7 Effective communication is essential between the pilot and ATCs. Moreover, ATCs work in a profession in which any disturbance in the communication provided during flights may lead to misunderstandings and compromise important flight information.
A previous study reported the presence of dysphonia in 44% of ATCs who were not always aware of the presence of this vocal deviation. The work environment and presence of risk factors, in addition to high levels of stress and great vocal demand, are combinations that can lead to the occurrence of dysphonia. If the main reason to seek medical care is the awareness of a problem, it must be considered that ATCs may not understand the seriousness of the presence of dysphonia, which postpones the diagnosis and increases the risk of a misleading communication between ATCs and pilots.
In this study, no statistically significant differences were observed in the rate of hoarseness and vocal tract discomfort for the variables ''time of working as an ATC'', ''age'', ''gender'', ''professional activities other than ATC'' and ''professional activities that consumes the most time''. Approximately 15% of ATCs reported other professional activities, which is far less than that among a sample of university teachers from a private institution in São Paulo (Brazil). 6 With regard to the workplace, the percentage of both symptoms was higher among ATCs who considered their air pollution intolerable. Many studies have observed correlations between vocal complaints and air quality in teachers 16---19 ; this was specifically noted in a pilot study with an inhalation challenge test. 20 Furthermore, the percentage of vocal tract discomfort was higher among those who considered their workplace a very tense and stressful environment. Nerrière et al. found an association between psychological distress and voice issues. 21 Indeed, it should be noted that stress is associated with a phonation pattern due to greater effort by the laryngeal muscles, which is usually associated with vocal tract constriction, and poor vocal fold vibration, which reduces the efficiency of voice production and projection. Vocal tract compensation can be frequent, contributing to voice production worsening.
Although there was no association between vocal symptoms and workplace in terms of noise, Ishikawa et al. 22 observed that dysphonic speech is relatively harder do understand in the presence of background noise as compared with normal speech.
Among ATCs, a small percentage (14.8%) reported receiving care or taking medications for their throat and/or voice. Additionally, only 9.2% sought medical advice because of vocal symptoms. Moreover, the percentage of hoarseness was higher among those who experienced moderate difficulty working because of vocal problems, which may explain the higher percentage of hoarseness among those who seek medical advice because of hoarseness. As stated before in the studies with university teachers, 7 it is interesting how specific vocal symptoms markedly influence whether individuals seek medical care.
In contrast, the percentage of vocal tract discomfort was higher among those who were stressed and anxious and among those worried about their health care.
These findings justify increasing the care and guidance given to ATCs, not only in the workplace but in any environment.
The limitations of this study include the fact that the sample came from a single APP; thus, these data cannot be generalized to ATC in other APPs around the country.

Conclusion
Among ATCs, the percentage of vocal tract discomfort was almost twice that of hoarseness. Both symptoms were present in ATCs who considered their workplace as having an intolerably polluted environment. Vocal tract discomfort was related to tense and stressful environments, and hoarseness was related to difficulty in using the voice at work.