gms | German Medical Science

Four main categories of risk factors for voice problems have been identified [1]

1.

Voice loading: e.g. the average daily speaking time

2.

General health condition: e.g. gastroesophageal reflux

3.

Environmental factors: e.g. dust, dry air, background noise.

4.

Psycho-emotional factors: e.g. Type D personality (described as the tendency to experience a high joint occurrence of negative affectivity and social inhibition).

On the basis of telephonic interviews Roy et al. [2] showed that being a teacher, being a women, having more than sixteen working years in education, being between 40 and 59 years old and a family history of voice problems are all associated with voice problems. These factors might be indicating a bigger chance to develop a voice problem.

A common characteristic of a majority of occupational voice users consists of the ‘intentionality’ of their voice (although this has not been really investigated from a scientific point of view): they need to « operate » on the listener, to reach a goal, to attain an end: consequently their voice use is a permanent challenge, with the risk to fall short of the mark, and this logically induces some kind of mental stress. Intentionality of voice supposes in general an enhanced dynamic range, as well in Fo as in intensity and in speech rate, simply in order to closier fit the underlying content and meaning. Physiologically it means an increase of muscular activity in all concerned anatomical structures [3]. Furthermore, in some of these categories of voice use, the performer chooses for specific resonance characteristics, as singing or acting formant, or formant tuning.

Monitoring these voicing conditions should be able to demonstrate the differences in prosody, speech rate, vocal attacks, formantic differentiation etc.

Most European contries handle a specific insurance system for occupational diseases, and this raises a double question of medico-legal expertise: on the one hand «Can the worker-patient who claims for compensation be considered as ‘at risk’ for the disease?», and on the other hand «Is the objectivated disease of the claimant related to the occupational activity?».

Defining the concept of being “at risk” is an important medico-legal issue: e.g. according to the Belgian law on occupational diseases “there is an occupational risk when

1.

the exposure to the harmful influence is inherent in the practice of the occupation,

2.

this exposure is distinctly higher than that of the general population,

3.

this exposure is, among the exposed persons, according to generally accepted medical knowledge, the main cause of the disease”.

The relative risk of occupational voice users for developing voice disorders, appears – as reported in the literature – curiously low from a point of view of insurance medicine. The relatively low (around 1–2) relative risk, as reported by Thibeault at al. [4] is contrasting with the percentage of occupational voice users treated in current clinical practice. However practically all the available publications are based on questionnaires, telephonic inquiries, self-reports, and not on objective findings. Furthermore these studies cannot make the difference between purely subjective experiences, as vocal fatigue, muscle tension dysphonia (the dysphonia being objectivable by acoustic analysis), and actual visible tissue reactions to phonotrauma, particularly vocal fold nodules.

Studies dealing with epidemiological aspects of vocal fold nodules are scarce [5]. There is an urgent need to focus on occupational voice patients with phonotraumatic lesions, and validly comparing them with controls (e.g. patients with seasonal allergic rhinitis, or occupational voice users without voice problems) from the point of view of occupational history, working conditions, psychological traits and possible biasing factors as gastro-esophageal reflux, smoking and non-occupational voicing habits.

In the past the relative failure to investigate voice use and the impact of overuse has resulted in a significant gap in the evidence base of occupational health and safety research [6]. Dosimetry and monitoring should currently fill this gap.

Within occupational voice users, particularly teachers, it is important to identify subgroups with higher relative risks, as e.g. music teachers and teachers of physical education / swimming. A few existing recent articles [7] seem to point out that this increased relative risk is relevant. Laryngoscopic investigations should be included. More data collected from dosimetry and monitoring in various countries and education contexts would make possible meta-analyses, as these strengthen the evidence and convince lawyers.