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Year : 2005  |  Volume : 7  |  Issue : 27  |  Page : 27--37

Noise exposure and subjective hearing symptoms among school children in Sweden

KM Holgers1, B Pettersson2,  
1 Department of Audiology, Sahlgrenska University Hospital, Sahlgrenska Academy, Göteborg, Sweden
2 National Board of Health and Welfare, Supervision Department, unit for Environmental Health Stockholm, Sweden

Correspondence Address:
KM Holgers
Department of Audiology, Sahlgrenska University Hospital, Sahlgrenska Academy, Göteborg


Objective: The aim of the present study was to evaluate factors of importance for the experience of temporary threshold shift (TTS), noise- induced tinnitus (NIT), spontaneous tinnitus (ST) in school children. Subjects and Methods: A total of 671 students aged 13-16 years old were asked to fill in a questionnaire containing items concerning TTS, NIT, ST, hearing loss (HL), heredity for HL, noise exposure, history of otitis media, symptoms of anxiety and depression, psychosocial factors and habits, life satisfaction, chronic medical conditions, age, gender and height. The questionnaire was filled in during school hours. Results: Correlations were found with exercise and eating habits, sleep disturbances, BMI, depressive and anxiety disorders, heredity for HL and noise exposure dosage. The risk for TTS was nine times higher in students who reported having a verified hearing loss than in subjects without subjective or verified complaints of hearing loss. The risk for NIT was approximately four times higher in the group who visited concerts 6-12 times per year as compared to those who never attended concerts. There was almost a threefold increase in the risk for ST in the group that sometimes experienced TTS, as compared to those without TTS, and a tenfold increase in risk for ST in those who reported having a verified hearing loss. Conclusion: In school children, exposure to leisure noise is correlated with tinnitus and the risk increases with increasing noise exposure. Sensitivity to subjective hearing loss has similar risk factors as seen for metabolic syndrome and we suggest that this sensitivity may be another side of metabolic syndrome.

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Holgers K, Pettersson B. Noise exposure and subjective hearing symptoms among school children in Sweden.Noise Health 2005;7:27-37

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Holgers K, Pettersson B. Noise exposure and subjective hearing symptoms among school children in Sweden. Noise Health [serial online] 2005 [cited 2020 Nov 29 ];7:27-37
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Although there are many reports on the impact of leisure noise on hearing, the scientific evidence of a relation between leisure time noise and sensorineural high frequency hearing loss (SHFHL) in young people is inconclusive and further research is needed. However, excessive exposure to loud music has been associated with increased hearing loss and/or tinnitus by several researchers (Fearn 1976, Babisch et al. 1988, Meyer-Bisch 1996, Struwe et al. 1996, Ising et al, 1997, Mercier et al. 1998, 2001).

Mazelova et al. (2001) reported that a single four-hour exposure to 94 dB amplified music may induce marked changes of the outer hair cells and can result in temporary or even permanent changes to the auditory system. In a review, Maassen et al (2001) estimated that about 10% of young people will suffer irreversible noise-induced hearing loss in both ears, of at least 10 dB at 3 kHz, after ten years of exposure to music played on personal cassette players (PCPs) and attending discotheques and concerts. In 1996, Meyer-Bisch reported a significant increase in hearing thresholds in young people who used PCPs (Personal Cassette Players) > 7 h/week as compared to those who used PCPs 2-7 h/week and to their matched controls. The same was true for subjects who attended rock concerts at least twice a month in comparison to their matched controls. In contrast, Wong et al. (1990) did not find these differences between users and nonusers, nor did Hoffman et al. (1997), Axelsson (1996), Passchier-Vermeer (1999), Meecham and Hume (2001) and Mercier and Hohmann (2002) observe any clear association between hearing impairment and sound exposures in discotheques and nightclubs or at pop and rock concerts.

Still, there is reason to believe that leisure noise may be an important health risk. Music often includes impulse noise and much circumstantial evidence exists that impulse noise is more harmful than continuous noise. A level of 90 dBLAeq 8 h has been considered acceptable for music exposure, however, and this is 5 dB higher than for occupational noise exposure. The Swedish Board of Health and Welfare are presently investigating these limits. The assumption that music is less hazardous than occupational noise was based on studies on hearing in professional musicians and on an experimental study of ten volunteers (Axelsson and Lindgren 1981a,b; Lindgren and Axelsson 1983). However, 20-year-old music students in Goteborg reported a sevenfold higher occurrence of subjective hearing loss than the normal population of the same age, 20% and 2.7%, respectively (Nebeska et al. 2000; SCB, Sweden, 2001). In a review of the literature, Palin (1994) found a firm association between live rock and roll music and hearing loss in rock musicians, but the reports gave conflicting results among classical musicians. This is in accordance with a recent follow-up where 74 % of the professional rock and jazz musicians had hearing symptoms. Among the professional classical musicians, however, the authors conclude that no severe hearing loss could be attributed to exposure to musical noise (Kahari et al. 2002).

The reported frequency of possible noise ­induced hearing loss (NIHL) in children varies greatly between studies. Barr and colleagues (1973) reported that, of the 2135 four-year-olds in their study, 0.2% of the boys and 0.1% of the girls had a high frequency hearing loss (HFHL), while Lipscomb (1972) found that 73% of the young subjects (n=1410, 16-21years old) had HFHL and reported a significant correlation between HFHL and exposure to gunfire noise. It is obvious that the difference in age alone cannot explain the difference between these two reports. The prevalence of a noise-induced hearing threshold shift among American children six to 19 years was estimated to be 12.5% (Niskar et al. 2001), but this figure was later questioned by Green (2002) on the grounds of the broad definition of NIHL used by Niskar.

There are many reasons for the great variation between studies, such as a lack of adjustment for important confounders, limitations in exposure characteristics and the diversity in how noise induced hearing loss is defined.

To diagnose a hearing loss as noise-induced, there must be both a damaging noise exposure and a threshold shift in the audiogram. However, most of the studies in the literature do not include baseline audiometry. A common classification of NIHL is a notch at 4 kHz (Passchier-Vermeer 1974, Rytzner and Rytzner 1981, Sataloff 1994, McBride 2001a,b), but an audiometric profile may include unexposed individuals. The distribution of hearing threshold levels in the general young population often includes a dip at 6 kHz (Lutman and Davis 1994).

There is very limited knowledge of noise ­induced and spontaneous tinnitus in children, and most of the studies that have been reported have included very few subjects.

For children with normal hearing, the prevalence of tinnitus is reported to be between 6% and 36% (Mills et al. 1986, Nodar 1972, Nodar and Lezak 1984, Baguely and McFerran 1994, Graham 1984, Graham and Butler 1984, Stouffer et al. 1991). The variation in the prevalence reported in different studies is greater in children than in adults; this might reflect the difficulties in interviewing children as well as the differences in how tinnitus is defined.

The prevalence of tinnitus in children who have a hearing loss is reported to be higher than in subjects with normal hearing and has been described to be as high as 76% (Mills et al. 1986, Nodar 1972, Nodar and Lezak 1984, Baguely and McFerran 1994, Graham 1984, Holgers 2003a). Unexpectedly, Graham and Butler (1984) reported that tinnitus was perceived more often by children with a mild to moderate hearing loss (66%) than among children with a severe hearing loss (29%). In seven-year-old children (n=961), no difference in hearing was found in those with or without an experience of tinnitus (Holgers 2003). In the latter report, 2.5% of the children reported having experienced noise-induced tinnitus.

In a pilot study including 274 children nine to 16 years old in a school in the Goteborg area, a majority of the children reported experiences of noise-induced tinnitus. It was found that the higher the age, the greater number of students had experiences of tinnitus. Roughly? Nearly? Half of the children also experienced tinnitus without a preceding noise; 14% of the children experienced tinnitus every day and an additional 2.2% had tinnitus always. Girls perceived tinnitus more often than boys (Holgers, 2002).

To our knowledge no other reports exist that include statistical analyses identifying factors of importance for the severity of tinnitus in childhood. However, data on more than 90 children and adolescents seeking help at the Department of Audiology at Sahlgrenska University Hospital showed that an important factor for suffering from tinnitus, according to the Tinnitus Severity Questionnaire, was a high anxiety level on the HAD scale (Juul and Holgers 2004).

Kentish et al. (2000) reported that many of the children with tinnitus (n=24) who had been referred to the department of psychology suffered from symptoms of anxiety. This is in accordance with Rosanowski et al.'s (1997) description .

The aim of the present study was to evaluate factors of importance for the experience of tinnitus in 13-16-year-old school children by means of a self-assessment questionnaire that included questions concerning temporary threshold shift (TTS) hearing loss, heredity for hearing loss, noise exposure, history of otitis media, symptoms of anxiety and depression, psychosocial factors and habits, life satisfaction, chronic medical conditions, age, gender, height.

 Material and methods


The study included a total of 671 students: 337 students, aged 13-15 years, (49% boys and 51% girls) at the upper level of the Swedish nine year compulsory school and 334 students, aged 16 years (63% boys and 37% girls) at the first year of the upper secondary school. The students answered the questionnaires during school hours, and a person from the health care unit was present in the classroom at the time of the assessment to sort out any perceived ambiguities in the questionnaires.


The questionnaire included three double printed pages (the questionnaire was six pages long?). The health care units of the schools provided the first page of the questionnaire, which was the health questionnaire for students in the upper level of compulsory school and the upper secondary school that was used by the units. The second page consisted of questions concerning hearing and noise exposure. The questions and answer alternatives from these two parts are given in [Table 4]. The third page included the 14 questions from the Hospital Anxiety and Depression scale (HAD). This is a questionnaire widely used to identify depressive and anxiety disorders in individuals seeking help for somatic conditions and may be used both for adults and children (Zigmond and Snaith, 1983, White et al, 1999).


Pitman Non-Parametric Permutation Tests (including Fischer's permutation test, when appropriate) and step-wise logistic regression analyses were used in the statistical analyses (Bradely 1968). The analyses were two-sided and included the subjects from both schools together. Odds ratio refers to the chance of an event versus the chance of a non-event. The odds of an event is defined as the probability of the outcome event occurring divided by the probability of the event not occurring. The odds ratio for a predictor tells the relative amount by which the odds of the outcome increases (OR. greater than 1.0) or decreases (OR. less than 1.0) when the value of the predictor value is increased by 1.0 unit.

If there are more than two values in the independent variable, odds ratios describe the mean value of the increased risk for each step between values of the variable (i.e. two values=one step, three values=two steps and so on).


Descriptive statistics

[Table 1] gives the overall experiences of tinnitus and temporary threshold shift (TTS) for all subjects (n=671).

The numbers of subjects from the first year of the upper secondary school (334 students; 37% girls) are comparable to the subjects from the upper level compulsory school (337 students; 51% girls), although there were more boys in the upper secondary school.

The data on hearing symptoms and noise exposure reported at the two different schools are presented separately in [Table 2] and [Table 3]. The subjects' data concerning experiences of noise­ induced tinnitus (NIT), spontaneous tinnitus (ST), both NIT and ST or no experience of tinnitus are described separately for each tinnitus category: reported TTS, how often tinnitus occurs, how often tinnitus is annoying, worry about tinnitus, noise exposure (e.g. freestyle more than 7h/week, concerts, discos/clubs, firecrackers or shooting) and reported subjective or verified hearing loss.

Non-Parametric Permutation Tests (Pitman, Fischer)

The results of the permutation tests are shown in Table 4.

Multivariate step-wise logistic regression analyses

The statistically significant correlations in the permutation tests were included in step-wise logistic regression analyses. The results are presented as odds ratios. The important factors for having experienced TTS were the following: NIT (odds ratio: 3.4); hearing loss (odds ratio: 3.1 two steps); smoking/use of snuff (odds ratio: 2.7); heredity of hearing loss (odds ratio: 1.3). The most important factors for having experiences of NIT were the following: TTS (odds ratio: 2.0, three steps); concerts (odds ratio: 1.4, four steps); discos/clubs (odds ratio: 1.4, four steps).

The most important factors for experiencing ST were the following: hearing loss (odds ratio: 3.3, two steps); TTS (odds ratio: 1.4, three steps); enjoying life (odds ratio: 0.9, ten steps); finding it easy to make friends (odds ratio: 0.3).

The odds ratios given above are the mean values of each increased risk between each step of the value level. For predictors including more than one step, the effect of the first two steps of the value levels in each variable was calculated. For predictors with ten steps, however, the effects of changes from the 5th to the 10th steps were calculated.

The odds ratio was 9.3 for TTS when comparing subjects who reported a verified hearing loss and subjects without any complaints of hearing loss (subjective or verified).

All the predictors that emerged for NIT had more than one step. The odds ratio for the group who visited concerts 6-12 times per year, as compared to those who never went to concerts, was 4.4 and the corresponding ratio for visiting discos/clubs was 3.8. For the group who sometimes experienced TTS, in comparison to those who did not experience TTS, the odds ratio for NIT was 8.4 times higher.

The increase in the risk for ST in the group who sometimes experienced TTS as compared to those without TTS was 2.8 and was 10.6 for those who reported verified hearing threshold shifts compared to those without any complaints of hearing loss (subjective or verified). The variable "enjoying life" had value levels from 0­10; for this variable, the risk for ST, for a change from 10 to 5 (0= very bad, 10=very good), was 1.7 times higher.


Our study is based on self-assessment questionnaires and takes into account many of the possible confounding factors that have been suggested in the literature to be important for the hearing function and that are described in the introduction.

The two main arguments for assuming that leisure time noise is a risk factor in teenagers are that the audiometric configuration resembles that of NIHL (i.e. the 4 kHz notch) and the sex distribution, as boys are considered to expose themselves to more noisy activities than girls. A gender difference of 4 kHz notches is present as early as four years of age (Barr et al. 1973), however, and this can hardly be explained by differences in noise exposure. Even though most studies show that HFHL is more common in boys than girls, and males are believed to be more susceptible to noise than females (Royster et al. 2000), there is also an age-induced SNHL (Stenstrom and Ingvarsson 1994). In the present study, we found no gender differences in TTS, NIT or ST but did note that there was a higher prevalence of TTS, NIT and ST with increasing age. This is in agreement with an earlier study where noise-induced tinnitus was 20 times higher in a group of 13-16-year-old children than among seven year olds (Holgers, 2003ab). This increase may be the result of changes in behavior and attitudes to noise exposure.


In our study, temporary threshold shift was strongly correlated to noise-induced tinnitus, heredity of hearing loss, smoking/use of snuff and hearing loss in the subjects.

Many authors have suggested that heredity for hearing loss is of importance for a diagnosis of hearing loss. Approximately one third of all hearing loss in preschool children born in Sweden is judged to be caused by genetic factors (Thiringer et el. 1984; Darin et al. 1997) Sehlin et al.1990). In the UK, approximately 25 % is estimated to be of genetic origin (Das 1996; Sutton and Rowe 1997), and heredity for hearing loss increases the risk 14 times for hearing loss in the child (Fortnum and Davis, 1997). Deterioration of hearing during military training is related to the hearing status on reporting (Klockhoff et al. 1986). However, smoking, which together with using snuff increased TTS, has been reported by some authors to have the opposite effect on TTS (Dengerink et al. 1984) or a non-effect on PTS (Kamal et al. 1989).


The most important factors for having experiences of NIT were having experiences of TTS and the risk for NIT was higher with an increasing number of TTS. It was also found that the more the subjects had exposed themselves to noisy activities, such as going to concerts, discos or clubs, the greater was the risk for NIT. As earlier described, there are some reports that indicate correlations between leisure noise and hearing loss and other studies that do not reveal this relation. Our study supports a relation between leisure noise and development of NIT.

A history of recurrent otitis media did not emerge as being as important for NIT as TTS and noise exposure, but there was a statistically significant correlation to NIT. Job et al. (2000) reported recurrent otitis media to be a risk factor for hearing loss among noise-exposed men, while no difference in hearing was found between noise-exposed and unexposed men with no history of recurrent otitis media during childhood. The correlation indicates that a history of recurrent otitis media may be of importance. However, it may be triggered by the same factors that cause hearing loss and may possibly be of genetic origin.


According to the multiple logistic regression analyses, hearing loss reported by the subject and a larger number of TTS increased the risk for ST significantly, while the risk decreased significantly if the person enjoyed life and made friends easily. The significant correlations of dissatisfaction in school, high scores on the anxiety subscale of the HAD, feelings of sadness and sleep disturbances, as described in Table 4, were not as important as the factors that emerged in the regression analyses. However, the items concerning, how the subjects enjoy life and are able to socialize with classmates may easily be interpreted as symptoms of anxiety and depression when these items are given a low score.

It was also interesting to find that having experiences of TTS or NIT also significantly correlated to higher levels of anxiety, feelings of dissatisfaction in school and sadness.

Strong correlations have been observed with depressive disorders in adult tinnitus patients and evidence has been presented that supports a role of 5-HT in the perception of tinnitus (Simpson and Davies, 2000). It has been speculated that there is a dysfunction in the serotonergic system in tinnitus sufferers and that the same mechanisms that cause anxiety and depressive disorders may also cause suffering from tinnitus (Holgers et al. 2003).

Because of the strong correlation between TTS, NIT and ST, there is reason to believe that audiological disturbances are a prerequisite for spontaneous tinnitus, but it is also possible that the same mechanisms that cause a vulnerability to perceiving tinnitus symptoms may cause a vulnerability to perceive TTS and NIT.


In school children, correlations are found between the subjective hearing symptoms and exercise and eating habits, sleep disturbances, BMI, depressive and anxiety symptoms, heredity for HL and noise exposure dosage. The sensitivity to subjective hearing loss has similar risk factors, as seen for metabolic syndrome, and we suggest that this sensitivity may be one aspect of metabolic syndrome[57].


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