Assessment Of Noise Induced Hearing Loss By Students Using Earphone And Headset In Naspoly

ABSTRACT

Voluntary exposure to loud noise may cause hearing loss and increase the prevalence of hearing impairment among adolescents. Noise-induced hearing losses (NIHL) have become more common among adolescents because of increased exposure to personal music players. Many adolescents used to listen to music by headphone. We aimed to assess whether the use of earphones has a significant effect on music-induced hearing impairment in teenage students.

ACRONYMS AND ABBREVIATIONS

NIHL -noise-induced hearing loss

ONIHL- occupational noise-induced hearing loss

ISO -International Organization for Standardization

CINAHL -Cumulative Index to the Nursing and Allied Health Literature

SPLs- Sound Pressure Levels

PTS -permanent threshold shift

TTS -temporary threshold shift

NIPTS -noise-induced permanent threshold shift

NIL -Noise Immission Level

ARHL- age-related hearing loss

STS -standard threshold shifts

HPDs -hearing protection devices

OSHA -Occupational Safety and Health Administration

HCA- Hearing Conservation Amendment

NIOSH -National Institute for Occupational Safety and Health a measure of noise that takes account of both the intensity of the sound and its duration

CHABA -Committee on Hearing, Bioacoustics, and Biomechanics

AHAAH- auditory hazard assessment algorithm for the human ear

DoL- Department of Labour

REAT- Real-Ear-at-Threshold

MIRE- Microphone-in-Real-Ear

HL- hearing level

SEL -sound exposure level

APV- Assumed Protective Value

IQR- inter-quartile range

DRC- Damage Risk Criterion

PCP- Personal Cassette Player

(NIHL) – Noise-induced hearing losses

CHAPTER ONE

• INTRODUCTION

Noise-induced hearing loss (NIHL) is a common and preventable disability, and it can be caused by recreational noise and leisure activity such as listening to music player devices. NIHL is one of the most important problems of social and public health. For reducing NIHL, policies mostly focus on reducing environmental noise to prevent hearing loss among adults, whereas many studies have shown that NIHL is increasing among students.

In the United States, studies of screening tests for hearing have revealed an increase in hearing problems for children at ever-younger ages and demonstrated that 14.9% of the children aged 6 to 19 years have low- or high-frequency hearing loss in at least one ear, and 12.5% had audiometric evidence of NIHL. Another study among adolescents in the United States showed that the prevalence of any hearing loss increased significantly from 14.9% in 1988-1994 to 19.5% in 2005-2006, and in 2005-2006, hearing loss was more commonly unilateral.

Nowadays, adolescents and young adults consciously expose themselves to loud noise or music for long periods of time and they are unaware of its consequences. NIHL in children and young adults has been linked to recreational noise and leisure activities. Lee et al. showed that continuous use of earphones for three hours led to about 10 decibel (db) increase in the hearing threshold. Moreover, with regard to increase in the use of portable music players and use of portable entertainment devices such as mobile phones, there is a concern about the hearing damage and hearing problems which may finally result in hearing loss.

In society today, people use earphones not only for listening to music, but also for eliminating the surrounding noise in the street, bus, taxi, or other transportation systems, all of which hurt ears and cause hearing loss. Hearing impairments or hearing loss may not be recognized for many years; so, treatment and intervention maybe difficult when it is detected. The existence of chargeable and durable batteries is a main reason for listening to music using portable music player devices. Most of the young adults listen unduly from portable music player devices and this issue can cause ear and hearing problems. The main problem is that usually adolescents listen to music with loud sound.

As stated above, listening to loud music for long periods of time especially with earphones may predispose the person not only to hearing loss but also to ear infection, tinnitus, and dizziness. Therefore, studies about listening to music in societies especially among students are important in planning for prevention and education about using patterns. Unfortunately, there is no information about the patterns of using earphone and music players among students.

1.2                                           BACKGROUND OF THE STUDY

Pollution experts and environmental toxicologists constantly warn the public about chemical and other airborne factors that can be a danger to their health, but one problem that is rarely mentioned in the context of environmental hazards is noise-induced hearing loss. It is time that the dangers of exposure to excessive and chronic noise are seriously taken into consideration, as well as the growing evidence that it can cause irreversible hearing loss. Historically, the focus on acoustic trauma problems has largely been related to adults (eg, hearing loss in soldiers from the battlefields of world wars; workers in noisy industrial factories; and in the elderly, for whom a lifetime of noise exposure can hasten the onset of presbyacusis [age-related hearing loss]). However, since the advent of amplified sound in the music and entertainment industries, and the growing popularity of portable music and gaming devices among the younger population, noise-induced hearing loss in children is a serious and growing concern.

The present article is written to provide health care professionals with more information about noise-induced hearing loss in children. It briefly describes the pathophysiology of hearing loss, and explains what structures of the inner ear are vulnerable and can be damaged by loud noise exposure. Also, it reviews the current literature that relates to noise-induced hearing loss in youth, and discusses the practical consequences of reduced hearing ability in children (eg, in relation to education and quality of life). Finally, the article suggests some educational tools and guidelines that can help inform professionals (clinicians, teachers and caregivers) and children about the risks of noise-induced hearing loss, and offers some practical advice on hearing loss prevention.

1.3                                              OBJECTIVES OF THE STUDY

There is concern that sound via earphones and headphones attached to headsets used in NASPOLY may be a risk factor for noise-induced hearing loss (NIHL). Although there are some previous studies investigating exposure to noise from headphones, almost none have assessed the risks to students who use earphones. To assess the level of awareness among young university going students about NIHL caused personal music players (PMP) with headset/insert earphones. And also to document presence of other ear related symptoms associated with prolonged exposure to noise such as tinnitus and vertigo.

The aim of this study was to assess the prevalence and pattern of use of earphone and music player devices as a main risk factor of hearing loss in adolescents students of NASPOLY.

1.4                                           SIGNIFICANCE OF THE STUDY

The industrial and technological revolution may have propelled society to higher levels of achievement, but this progress has also made the world a noisier place in which to live. In fact, noise pollution is a growing health hazard and can be found almost everywhere. Car alarms, leaf blowers, gunshots, boom boxes, and traffic congestion fill our cities with decibels (the measure of sound intensity). Escaping to the country may not provide a quiet refuge, and even farmers are at high risk for exposure to noise from their farm machinery.

Unpleasant or unwanted sounds are not the only harmful noises to which we may be exposed. For example, the music at a concert and the pounding of a jackhammer on the street can be equally damaging to the inner ear. Loud sounds (acoustic energies) delivered with equal intensity or over extended periods of time, regardless of their source, are equally dangerous. Eventually, continued or repeated exposures to high intensity sound can cause acoustic trauma to the ear. This trauma can result in hearing loss, ringing in the ears (tinnitus), and occasional dizziness (vertigo), as well as non-auditory effects, such as increases in heart rate and blood pressure.

One-third of the 30 million Nigeria with hearing loss have an impairment that is at least partially attributed to excessive noise exposure. Noise remains the most common preventable cause of irreversible sensorineural (involving the ear’s sensory nerve) hearing loss.

1.5                                                PURPOSE OF THE STUDY

The purpose of this study is to access the level of health priority and awareness NIHL has among adolescents and young adults of a developing country. Although there has been research regarding occupational NIHL, there has been no research regarding recreational NIHL among PMP users in NASPOLY

1.6                                                PROBLEM OF THE STUDY

In this section, some of the current literature on the noise-induced hearing loss in children and young adults is reviewed. This is not an exhaustive or systematic review, but a representative sample of studies that all point to the growing problem. In terms of general population studies, a report from a large-scale American national health survey indicated that 12% to 15% of school-aged children have some hearing deficits attributable to noise exposure. In Canada, there are no large surveys that specifically address noise-induced hearing loss. Statistics Canada data indicate that 13% of children (up to 14 years of age) have some hearing disability, but it does not separate out specific etiology (8). WorkSafeBC (Workers Compensation Board of British Columbia), in a large survey (9) of young workers entering the workforce, report that over 20% have some early signs of hearing loss, but this includes all causes of hearing loss, not just noise-induced loss.

There are not many Canadian statistics, but there are plenty of data from other countries. In a Scandinavian study (10), a hearing test on 538 teenage boys revealed a hearing loss (greater than 15 decibels [dB]) in 15%. The characteristics of the loss indicated that the majority were related to noise exposure. Similarly, a German review (11) of clinical data estimated that one in 10 adolescents had some degree of noise-induced hearing loss from ‘leisure time noise’. In a recent Chinese study of 120 young users of ‘personal listening devices’, impaired hearing (loss greater than 25 dB) was found in 14% of subjects. A French audiometric survey of 1364 young subjects found evidence of hearing problems in 12% of the general population, and in a subgroup that often attended rock concerts or used ‘personal cassette players’ (more than 7 h per week), 66% had hearing loss. A similar finding was reported in a smaller group (n=24) of German teenagers.Many studies describe the increase in the use of personal entertainment devices and attendance of concerts where amplified sounds are enough to cause noise-induced hearing loss.

Recognizing that there is a real problem, many studies have focused on some of the specific causes, such as very loud signals from some cordless telephones, the types of headphones or earphones used in personal entertainment devices, and the actual levels of sound that are generated by earphone transducers . In addition, there are numerous other reports on other possible sources of noise trauma for children, including very noisy toys, cap guns and fireworks. Other research has assessed the risks of noise-induced hearing loss at specific entertainment venues, such as rock concerts (19) and ‘urban music clubs’ (20). There is even a published report (21) with the title “Can hockey playoffs harm your hearing?”, from a Canadian research team of course. All of these reports and studies confirm that there is a potential problem with noise-induced hearing loss at certain entertainment events. In noise-induced hearing loss from very high-level sound exposures, tinnitus is often reported. For example, in a Swedish study (22) of 55 boys (eight to 20 years of age) who were seeking help for tinnitus, the majority were found to have been exposed to excessive noise, mostly from recreational music. One study (23) suggested that after short-term exposure to (over-) amplified music, tinnitus may be more of a problem than any other hearing deficit.

To balance the evidence, some researchers have concluded from their data that there is no clear link between recreational noise exposure and hearing loss. For example, one research group (24) concluded that most young users of personal listening devices were at low risk for noise-induced hearing loss. However, these authors cautiously admitted that their study group did not include certain high-risk populations with greater noise exposures, and go on to strongly recommend educational sessions about the dangers of noise exposure. An extensive Australian survey (25) also concluded that there was “no widespread hearing loss caused by recreational noise”, but the authors did warn that “if recreational patterns remain the same”, teenagers will be at high risk for noise-induced hearing loss by their mid-20s. Indeed, there is a strongly held view (which this author also holds) that noise exposure effects are cumulative. Thus, over the short term, the effects of noise overstimulation may not be obvious, but the accumulated effects of damaging episodes will eventually lead to significant hearing deficits. An important point here concerns the redundancy of hair cells in the cochlea. There are many more sensory elements than needed, so considerable cell loss can occur before there are clinical signs of a problem. However, with repeated insults, the fixed complement of hair cells eventually runs out. This is one reason why noise-induced damage in early years may not immediately manifest, but may become a problem later in life.

To summarize, on a cautious note, a recent general review of the issue of noise-induced hearing loss in relation to school-aged children concluded that it is a major cause of hearing loss (in the United States), and that hearing impairment among children and teenagers is increasing mostly due to ‘voluntary exposure’ to loud noise (ie, using personal entertainment devices or attending amplified sound concerts).

There is a common categorization of the types of hearing loss, which distinguishes conductive loss, cochlear or sensorineural loss, and central hearing disorders. A conductive loss is anything that reduces the transmission of acoustic signals to the cochlea; this can simply be wax or other obstructions in the ear canal, or fluid build-up in the middle ear. Paediatricians will, of course, be familiar with conductive hearing loss that can accompany otitis media. In relation to noise exposure, it is possible to have intense acoustic trauma that damages the eardrum or the middle-ear ossicles, but this is rather unlikely in infants and children (unless they live in a war zone). For the most part, noise-induced hearing loss involves damage to delicate structures of the inner ear, particularly the hair cells, and is thus categorized as a cochlear or sensorineural hearing loss. The third category of hearing loss relates to a central auditory system disorder. A cochlear hearing loss cannot be absolutely separated from a central loss because any reduction or degradation of the peripheral auditory input will have an impact on central auditory function. Importantly, health care professionals dealing with infants should also recognize that in early life, the activity patterns that are present at the cochlear level are important for the development of the central auditory brain, and that cochlear disorders and even conductive loss may have significant impacts on the development of (central) mechanisms of hearing.

A broad classification of the types of hearing loss. While noise-induced hearing loss is usually categorized as a cochlear or sensorineural hearing loss, it may also be combined with a conductive loss, and will also impact on central auditory processing .

With regard to noise-induced hearing loss or acoustic trauma, Figures 2 and ​and33 show what can happen to the delicate hair cells of the cochlea after physical insult. The left panels of Figure 2 show normal hair cells, and a diagram (for one cell) showing how the stereocilia (hair) are organized. These stereocilia, when deflected by acoustic signals, cause an excitation (depolarization) of the hair cell that leads to neural activity in cochlear afferent neurons that make up the auditory (eighth cranial) nerve. For each cell, the stereocilia are neatly organized in a bundle. The individual ‘hairs’ are cross-linked, and when the whole bundle is displaced by sound signals, some of these links pull open membrane ion channels on the surface of the hair. Flow of ions (mainly potassium) through these membrane channels changes the hair cell receptor potential. These details are mentioned to emphasize that the micromechanical arrangements of stereocilia, their linkages and the membrane ion channels are delicate and can be damaged by acoustic overstimulation.

Scanning electron images illustrating normal cochlear hair cells (left) and immediately after noise trauma (right). The lower left diagram shows the normal linkages between stereocilia that are disrupted or broken in noise-induced hearing loss

The stereocilia of normal cochlear hair cells (left) compared with cells after acoustic trauma and in the process of complete degeneration (right). There is no natural regeneration of hair cells in the mammalian cochlea

In addition to the direct mechanical trauma that loud sounds can cause to the hair cells, there are also secondary effects that can cause further damage. Just as with a brain injury (eg, stroke), there can be an initial restricted lesion, but cellular byproducts that are released (eg, oxidative free radicals or excessive amounts of neurotransmitter) can cause more extensive damage. It is also possible that prolonged acoustic overstimulation can lead to local vascular damage and cochlear hypoxia, which in turn can cause damage to hair cells.

Everyone is born with a fixed number of cochlear hair cells. In humans (and all other mammals), they do not regenerate, and so preventive care should be taken. In some vertebrates (eg, birds), similar hair cells do regenerate after damage. New hair cells develop from local supporting cells, which act like a type of stem cell. There is evidence that in vestibular sense organs, the hair cells are capable of regenerating from supporting cells, but in the cochlea, this does not happen. Presently, there are considerable research efforts to determine whether cochlear hair cells can be made to regenerate, either by providing suitable growth hormones or by finding a genetic switch to turn on the cell differentiation process (4–6). Presently, however, the fact remains that if we kill hair cells by noise exposure, they are lost forever.

1.7                        CONSEQUENCES OF HEARING LOSS IN STUDENTS

For most health care professionals, hearing loss is largely described by the results of clinical tests, such as the audiogram or speech threshold measures. The general categories of loss range from mild, to moderate, to severe, to profound (each has a specific audiometric definition). In infants, hearing can be assessed objectively using auditory evoked potentials or otoacoustic emissions. Typically, a deficit will be described as a hearing threshold loss in dB. It is important to point out that such basic measures, while useful, do not always reflect a hearing problem. It is common to have a child with normal hearing thresholds, but with significant problems in understanding speech. In other words, the ability to understand complex sounds can be reduced before pure tone audiometric thresholds are apparent. Clinicians should recommend a comprehensive hearing evaluation, including speech discrimination tests.

Beyond clinical test results, there are broader ways of looking at hearing disability. The World Health Organization has a scheme for assessing and describing hearing problems. This model distinguishes impairment, disability and handicap. Impairment is the actual loss of sensory function quantified by the clinical tests mentioned above. Disability is the ‘activity limitation’ of an individual that results from the impairment (eg, a patient might not understand what you say, and needs to ask you to repeat words). Handicap is a measure of ‘participation restriction’ (ie, activities that a child may not be able to do because of the hearing problem). This might include making friends, keeping up at school or being excluded from training for a certain career. Here, one can separately consider the core as one-on-one interactions of a subject with a mother, a sibling, a teacher, etc. In the wider circle, there is broader communication and interaction with family and friends. Finally, there is the impact of the subject’s hearing impairment on society (including economic issues, educational achievement, employability and quality of life).

The consequences of hearing loss should be considered in broader terms than just the clinical measures of hearing threshold loss. dB Decibel; WHO World Health Organization

For a child with noise-induced hearing loss, the degree of deficit is likely to be mild or moderate, as opposed to severe or profound. However, such a loss might still be a barrier to effective communication, especially in noisy environments such as the school classroom. It should also be recognized that mild-to-moderate hearing losses may not be immediately apparent to a child (in the same way that many older persons do not recognize that they have age-related hearing loss). Parents and clinicians should be vigilant; it is worth repeating that measures of speech discrimination will more accurately reveal a hearing problem than simple audiogram or hearing screening tests. In a very young child, hearing problems can delay language development, and if information is being missed at school, educational achievements can be reduced. For adolescents, communication difficulties can lead to social isolation; there have been reports of suicide resulting from such situations. If hearing aid use is warranted, the adolescent may also have problems with the cosmetic appearance of the device or the stigma attached. The child may decide to not use the aid, or choose to retreat to a small group or become socially isolated. In any case, it can be assumed that there will be quality of life implications.

In public advocacy and education campaigns by The Hearing Foundation of Canada (THFC) , one strategy for promoting hearing loss prevention in children is to say “save your hearing for the music” In other words, if you love listening to your music now, you will lose that pleasure if you damage your hearing. The quality of life impact may also be felt at a later age when job opportunities are restricted because of the hearing problem itself or a reduced educational attainment. The impact may also be an economic one.

Sound Sense poster from The Hearing Foundation of Canada, targeting young people with the slogan “Save your hearing for the music”.