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编辑东声   2007年2月24日                                                                                     

The Present Status of Research on Presbycusis and Intervention in China

Tao Jiang  Zou Ling

Abstract: The latest survey indicates that China has more than 130 million senior people, accounting for 11% of this largest population in the world. From 2025 to 2050, this population will increase from 240 million to 400 million. Hearing loss associated with aging, also known as presbycusis, seriously affects the communicative abilities and compromises the life styles of the elderly people in China. While for the last decade, the focus of hearing health care has mainly been on pediatric population, today presbycusis and its consequences have caught the attention of the country. Efforts have been made to help the elderly; however, lack of well documented demographic data on the prevalence of presbycusis has significantly hampered the efforts to establish infrastructures for effective aural rehabilitation and clinical management of the elderly people suffering from auditory deficits and other communicative difficulties.

This paper intends to review the existed research articles, published in Chinese, on presbycusis and intervention, and to present our view of the present status of research in this direction. It is encouraging to notice that more studies were done in most recent years, demonstrating increasing interest from the research community. At the same time, it should be noted that because of inadequate study designs and poor controls of all measurement parameters, there is considerable variability in the outcomes of the studies. A wide range of prevalence has been reported from 22.5% up to 90%. The sampling sizes also vary from 150 subjects to 1454 while age intervals are different from one study to another. Only a few studies were carried out to determine the prevalence of central auditory processing disorder (CAPD) and other cognitive dysfunctions associated with elderly population in the country. The use of hearing aids is low among hearing impaired seniors. In the end, the authors will discuss the reasons that the present research on presbycusis is lagging behind and possible solutions will be explained and shared.   

1． Background

Hearing loss suffered by elderly people is termed as presbycusis, a hearing loss that needs to be taken seriously now. Very often, presbycusis is defined as being associated with the aging process. However, the Committee on Hearing, Bioacoustics and Biomechanics considers “presbycusis to be the sum of hearing losses which result from several varieties of physiological degeneration. These include insults due to noise exposure, ototoxic agents, polypharmacy, and medical disorders as well as the effects of physiological aging”^⑴. It is our belief that the above definition can better delineate the nature and consequence of this hearing impairment that has not only reduced the auditory ability of the elderly, but also caused communicative breakdowns in their daily life; therefore, presbycusis will be used in such a context throughout this paper.

The residents of the world are becoming older because of their prolonged life expectancies, especially in the developed countries. As a result, presbycusis has become the most common health problems on earth. In US, more than 7 million aged persons suffer from some degree of hearing impairment. Given the rapid growth in the population over 75 years of age, this population will surge to more than 11 million by the turn of the century^⑵. The recent position statement from Aged Persons with Hearing Impairment: Report of the Task Force on Hearing Impairment in Aged People released by the American Academy of Audiology clearly emphasizes that the aged the population will be accompanied by an increase in the prevalence and severity of hearing loss, due to the direct correlation between age and hearing loss. In 2004, the MarkTrak VII study in USA sent a short screening survey to 80,000 members of American households and the data then compared with that of the last 15 years. The results reveal that the hearing loss population has grown to 31.5 million. Since 2000, the most notable increases in hearing loss population size were noted in age 85 above with 92% topping on the list and the group of 54-65 had 27% increase^⑶. In Canada, according to the statistics from Canadian Association of Speech Language Pathologists and Audiologists, the seniors represent a fast growing segment of its population. 1 in 10 Canadians have a speech, language or hearing problem. Hearing loss is the third most prevalent chronic disability among older adults, 20% of adults over 65, 40% over 75 and 80% of nursing home residents have a significant hearing problem.

Communicative disorders experienced by elderly people are multifaceted in that they are not only suffering from hearing impairment, but also from other dysfunctions accompanied by aging, such as vision degeneration, speech understating difficulties, memory loss and so on. Among them central auditory processing disorder (CAPD) is believed to play a critical role in the reduction of communicative ability of the elderly. The present research on the prevalence of CAPD in the elderly has further confirmed the fact that the complex nature of presbycusis requires extreme caution and skills in its clinical diagnosis because of the involvement of CAPD. An Australian study, the Blue Mountains Hearing Study, has gained further insight into the CAPD. This study examined 2,015 Australians aged 55 years and older living in west of Sydney. They were assessed with a battery of behavioral and electrophysiological auditory tests. The results have found a high overall prevalence of CAP abnormality (76.4%) with age^⑷,⑸. Obviously, the high rate of CAPD among elderly people can certainly compound the complexity of presbycusis because one will have to separate the central disorder from the peripheral.  

As of Jan 6, 2005, the upsurge of China’s population growth reached the historic milestone of 13 billion people. By the end of that year, it increased by another 7.5 million in just 12 months with a total of 1,307,560,000.00. In fact, China has had a net increase of 10 million people each year. The latest survey indicates that China has more than 130 million senior people, accounting for 11% of this largest population in the world. From 2025 to 2050, this population will increase from 240 million to 400 million. At the same time, it should be noted that the traditional Chinese family structures have also undergone through significant changes in that today more elderly people live alone than ever before. For those age at 65 or above, 10.44% is a single while a couple living alone accounts for 11%. The family structure changes have further weakened the ability of the elderly to afford adequate health care, including hearing care.  

Like in developed countries, presbycusis is the most common hearing loss seriously affecting hundreds and thousands of elderly people in China. While in the last 10 years, in China, the focus of hearing health care was mainly on children, having resulted in significant improvement in the screening and rehabilitiaotn of paediatric hearing impairment. The increasing public awareness of hearing loss associated with children has been elevated to a new high level because the country has taken strong initiatives to address these serious problems through a series of legislative measures and regulations. For example, in 1990, the country promulgated the Law for Protecting the Disabled. Later, the People’s Congress passed the Development Plan for the Children of China and the Developmental Outlines of the Children of China between 2001 and 2010. In 1994, the State Council promulgated the Educational Act for the Disabled, including the students of deaf and hearing impairment. A joint position statement, issued by 10 national ministries and agencies of China in December 1999, identified hearing loss as one of the most severe health problems affecting the life quality, study and work of Chinese citizens.

The last census identified that China has about 60 million disabled people，about 5% of Chinese population. Among them are 11.82 million mentally retarded people, 8.77 million amputees, 8.77 million vision-impaired and 7.82 million multi-handicapped. However, among them are 26 million people with hearing and speech problem, a number equal to the entire Canadian population in 1990.  Those with severe-profound hearing loss are 7.2 million. Among them, there are three million deaf children, of whom 1.8 million are under the age of 14 and 740,000 are under 6. In comparison, less attention has been given to presbycusis at the same magnitude. There has been a very few studies on the prevalence of geriatric hearing loss in China. Consequently, a lack of demographic facts regarding the prevalence of presbycusis prevents from the provision of effective rehabilitation and management of senior people with hearing loss.

2. Present Studies on Presbycusis in China

In order to find out the present status of studies on presbycusis and rehabilitation provided to the elderly in the country, we have reviewed 32 major studies published in major Chinese journals in China from 1994 through present time. The articles cover a wide range of research interests from clinical evaluations to demographic studies as indicated in Table 1.

                Table 1. Research Focus among the Articles 

Apparently, there were more studies that concentrated on clinical evaluation of presbycusis, such as the comparison of standard audiometric testing with high frequency audiometry, the clinical features of presbycusis and so on. There were only 3 studies devoted to rehabilitation. It is interesting to note that one paper summarized a preliminary study of the treatment of geriatric hearing loss with traditional Chinese medicine (Zhao et al, 1997). The authors reported that among 78 patients treated, 53.85% of them improved their hearing and 73.72% experienced reduction of tinnitus after 30 days’ intake of Chinese medicine^⑹. However, due to lack of details of the study, it is difficult to objectively judge the efficacy of the treatments.

In order to understand how the demographic studies were designed and carried out, we have carefully reviewed those studies in detail. First, a wide range of prevalence of presbycusis was reported from 22.5% up to 90%. The sampling sizes of population varied from 150 subjects to 1454 while age intervals were different from one study to another. The details are summarized in Table 2

Table 2 A Summaries of Major Demographic Studies on Presbycusis in China

From Table 2, we can see that the reported prevalence were from 22.5% to 90%. The wide disparity was probably caused by inconsistent hearing loss criteria employed in those studies and other factors. For example, some studies used 26 dBHL or greater as the hearing loss threshold while others adopted 35 dB HL or greater. In some studies (Liu et al, 2000), the researchers attempted to use the averages of both speech and high frequencies to separate those with hearing loss from normal, thus yielding a low figure of 22.5%^⑺. In nearly all tests, speech audiometry was not administered other than pure tones. Lack of speech audiometry prevented from across reference check on the accuracy of pore tone findings, as widely used in clinics; furthermore, the magnitude of presbycusis could note be thoroughly assessed. The age inclusion criteria were inconsistent and age intervals not properly determined in the studies. As a result, the pure tone results of large groups of elderly subjects from 55 to 96 were all analyzed as in one group without any age breakdown, thus either underestimating the hearing loss of more senior patients or overestimating those relatively younger ones. Sampling sizes are also noted to be small in most of studies, ranging from 150 to 1434. Little or no testing on CAPD or cognitive ability was mentioned in all demographic studies.

In reviewing the articles on presbycusis, it is imperative to point out that in all of the studies very little information was provided with regards to the conditions of audiologic instrument, calibration standards and procedures, and testing environments. Table 3 details the testing conditions of those studies and none of them reported calibration standards employed, nor procedures applied. Except for one (Wang et al, 1998)^⑻, no testing environments were stated. Interestingly enough, one study (Huang, 2005) reported that they collected all the hearing data with tuning forks and live speech as testing signals^⑼.

Table 3 A Summary of Testing Conditions 

The most studies reviewed mainly focused on pure tones and peripheral functions, and there are a few studies on central auditory processing disorder and cognitive dysfunctions associated with elderly population in the country. Among the two papers touching on those aspects, one study (Zeng et al, 2006)^⑽ was found to have questionable research designs and methods used. The authors failed to understand the nature and role of speech reception threshold (SRT) testing, a measure whose “most important contribution is its indication of the accuracy of the pure tone findings” (Rintlemann, 1991)^⑾. In stead, they designed this speech test as an important assessment of speech discrimination for the measure of cognitive ability of the elderly, thereby compromising the outcomes of the study.

However, despite the problems exhibited in those studies, we believe that the data have shed light on the magnitude of presbycusis in China. It is very clear that more work is needed along this direction.    

3. Present Status of Geriatric Aural Rehabilitation

For the last 20 years, the outstanding economic achievements have dramatically improved the living standards and quality of health care in China. According to the latest statistics released by the ministry of Health of China, there are 18,703 hospitals and 207,457 clinics in the country with more than 3.36 million hospital beds to serve its large population. However, one should note that there are only 31 otolaryngology hospitals and 246 rehabilitation hospitals. Despite the fact the country has more than 1.9 million doctors, including those of Chinese traditional medicine, 1.3 million nurses, and 5.4 million medical technicians, otolaryngologists, those specialising in treating ear, nose and throat problems, are still a small group: only 632 licensed ENT physicians and 751 assistants. Lack of well trained professionals has been a growing concern because it directly prohibits from the provision of hearing health care to the elderly in China^⑿,⒀.

In 2005, twelve ministries and agencies of the country jointly designated March 3 of the year as the day of Ear Care for Seniors: Healthy Hearing and Happy Life. This initiative along with others has increased the pubic awareness of presbycusis and its serious consequences on both individuals and the society in general^⒁. However, it is well understood that at the present time, hearing healthcare for the elderly largely remains in its infant stage with limited resources and nearly nonexistent infrastructures. Among all, the biggest challenge that the country is facing is a severe shortage of hearing professionals are providing needy services to a large population. Although there are nearly 5,300, or 30% of the hospitals, providing audiological services and hearing aid dispensing and more than 1.9 million doctors practising medicine in China, only 632 licensed otolaryngologists (ENT doctors), 751 assistants (2005) and a small number of qualified audiologists work in hearing healthcare. In comparison, the United States has about 9800 audiologists and 5200 otolaryngologists. In Canada, more than 600 audiologists have registered with the Canadian Association of Speech-Language Pathologists and Audiologists. Including non-registered audiologists, the number is estimated in excess of 1000^⒂. 

Today in China, hearing aid use in general is fairly low, and we believe that this figure is even lower for the elderly. There is very little demographic data concerning the use of hearing aids for the elderly people in China. We can only reply on the limited information to make an educated estimate. We have reviewed five papers that reported the use of hearing aids. Like in other studies, the disparity of the results from those studies is quite significant, ranging from only 1.1% to 16.52% in hearing aid use^{⑺~⑼,⒃,⒄}. Huang and his research team (2006) found that out of 683 hearing impaired elderly patients, only 8 wore hearing aids. In comparison, MarkeTrak VII study revealed that for those at age 85, 60.6% elderly people use hearing aids; at age 75～84, 44.1%  hearing aid users and at age 65～70, the percentage was to 31.3%. Once again, a lack of proper study designs and poor control of variations are believed to be responsible in those studies, thereby limiting us to make any generalization.

In terms of styles of hearing aids, body types are still popular at affordable prices of RMB 400-1000 (US$ 50-125) despite the fact that behind-the-ear (BTE) hearing aids and in-the-ear (ITE) hearing aids are becoming more accepted by the elderly. In one study (Liu, 2000), 63% of patients used body hearing aids while 28% used BTE^⑺. But we can see there is an increasing trend to favor the use of BTE hearing aids, as reported in one study (Ren, 2002) where a half of patients chose to use BTE hearing aids and the other half still selected body aids.

In general, analogue hearing aids account for most of devices used, although digital instruments have begun to increase. We have noted that unilateral fitting is still predominant in most of hearing aid fitting. In estimate, the average age of hearing aids is approximately 5 years or older. In most cases, hearing aids are purchased by their family members and those elderly people tend to live in large cities.

In all of the studies, the main reasons that the elderly refused to use hearing aids are (1) the patients could still cope with their daily communication even without hearing aids, (2) they have low motivation to use hearing aids even though their communication is affected, (3) the infrastructure for providing rehabilitation services is still underdeveloped, and (4) most imported hearing aids are very expensive for ordinary elderly people. It should be reiterated that we failed to find any specific geriatric aural rehabilitation programs from those articles.

4. Recommendations

It is clear that hearing health care just started in China and the care for geriatric people is at the beginning. Our review of the present studies on presbycusis and rehabilitation indicates that progress has been made in this direction but there is more to be done. We also recognize that audiology is an emerging profession in this country and the infrastructures for the provision of audiologic services are being built up. Therefore, we strongly believe that fundamental changes are needed to support and to facilitate more thorough and comprehensive studies on presbycusis in China. It is for those wishes that the following recommendations are made:

1. Audiologists should be recognized as one of the leading professionals to provide services to the elderly, and therefore be officially accepted as an independent occupation in the country. A lack of recognition can have a profound impact on the development of audiology as well as the quality of serving the elderly hearing impaired people.

2. All medical professionals engaged in research or services of aural rehabilitation should receive adequate training on the nature of presbycusis and techniques of geriatric aural rehabilitation. Training can take different formats to satisfy unmet needs of different levels. More importantly, there is a need to create standardised educational curricula consisting of basic components of audiology.

3. Like infant hearing screening, the government of China should take initiatives to encourage the research community to get involved in the field of geriatric audiology. At the same, concerted efforts should be made to collect scientific data on the prevalence of presbycusis by means of well designed demographic and epidemiological studies. A better understanding of the scope and severity of presbycusis can guide our practice in clinical diagnosis of all communicative difficulties associated with hearing loss and delivery of aural rehabilitation.

4. It is well understood that China is still a developing country with limited resources. A large scale of hearing screening of its older population requires substantial amounts of financial commitment and also asks for a great number of audiological instruments. Therefore, it is highly recommended that other assessment alternatives should be considered. For example, a number of questionnaires have been approved to be clinically reliable and valid for daily use, such as Hearing Handicap Inventory for the Elderly-Screening Version，or HHIE-S. This questionnaire has 10 self filled questions and easy to be administered. It has been found well correlated with pure tone results. Its sensitivity in office is 72% and in clinic 76% while the specificity is 77% and 71%, respectively. Therefore, we feel that this test can best meet the needs of screening a large number of people at little cost.

5. Considering the complex nature of geriatric aural rehabilitation, it is imperative to establish hearing and speech centers devoted to serving the elderly in the country. This can learn from the experience of setting up the similar centers for hearing impaired children. Based on its unique political and economic systems, China has demonstrated its ability to operate successful hearing and speech programs to more than 1.8 million children under age 14. According to the report from China Disabled Persons’ Federation, this single largest agency that the government has funded now manages more than 500 hearing and speech rehabilitation centers at the provincial levels across the country. Furthermore, a total of 1,732 similar centers have been set up by various levels of government departments and agencies. More than 5,000 personnel provide both hearing and speech services at those centers. This has been approved to be very effective and successful. Therefore, there is no doubt that geriatric programs follow the same path with modifications if needed.  

6. Finally, but not the last, as we can see from the research papers reviewed in this article, there is an urgent need to increase public awareness of presbycusis. This requires joint efforts from the government, the professional community as well as the society in general. The inherent complexity of hearing loss and its related consequences needs to be given extra attention for better understanding. Furthermore, communicative dysfunctions of different aetiologies can compound the auditory problems. Therefore, it is of great importance to educate the public and the medical professionals about the issues relating to hearing loss.

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