Notch polymorphisms associated with sensitivity of noise induced hearing loss among Chinese textile factory workers.

BACKGROUND: Noise induced hearing loss (NIHL) is a polygenic disease involving both genetic and environmental factors, and is one of the most important occupational health hazards worldwide. To date, the influence of Notch1 variants on the risk to develop NIHL has not been illuminated. This study was conducted to explore the effects of Notch1 polymorphisms on individual susceptibility to NIHL. METHODS: A total of 2689 industrial workers from one textile factory in east China were recruited to participate in the current study. Venous blood was collected, basic clinical data was obtained by questionnaires and pure-tone audiometry (PTA) tests were conducted by specialist physicians. Next we performed genotyping of three selected SNPs (rs3124594, rs3124599 and rs3124603) in the Notch1 gene in 535 NIHL patients and 535 controls. Subsequently, the main effects of the genotypes and their interactions were evaluated. RESULTS: Our results revealed that individuals with a GG of rs3124594, TT of rs3124603 (OR = 4.70 and 1.59 respectively) and the haplotype AAC (rs3124594-rs3124599-rs3124603) (OR = 14.95) were associated with an increased risk of NIHL in our study cohort. Stratified analysis showed that an increased NIHL risk was found in individuals exposed to work related noise for ≤16 years that also had the rs3124594 GG or rs3124603 CT/TT genotype with an OR of 4.20 and 1.73 respectively. Multifactor dimensionality reduction analysis indicated that rs3124594, rs3124599 and rs3124603 interacted with each other and were related to an increased risk to develop NIHL (OR = 3.60). CONCLUSIONS: The genetic polymorphisms rs3124594 and rs3124603 within the Notch1 gene are associated with an increased risk of NIHL in a Chinese population and could potentially be used as biomarkers for NIHL in noise exposed workers.

Analysis of audiometric notch as a noise-induced hearing loss phenotype in US youth: data from the National Health And Nutrition Examination Survey, 2005-2010.

OBJECTIVE: Bilateral audiometric notch (BN) at 4000-6000 Hz was identified as a noise-induced hearing loss (NIHL) phenotype for genetic association analysis in college-aged musicians. This study analysed BN in a sample of US youth. DESIGN: Prevalence of the BN within the study sample was determined and logistic-regression analyses were performed to identify audiologic and other demographic factors associated with BN. Computer-simulated "flat" audiograms were used to estimate potential influence of false-positive rates in estimating the prevalence of the BN. STUDY SAMPLE: 2348 participants (12-19 years) following the inclusion criteria were selected from the National Health and Nutrition Examination Survey data (2005-2010). RESULTS: The prevalence of BN was 16.6%. Almost 55.6% of the participants showed notch in at least one ear. Noise exposure, gender, ethnicity and age showed significant relationship with the BN. Computer simulation revealed that 5.5% of simulated participants with "flat" audiograms showed BN. CONCLUSION: Association of noise exposure with BN suggests that it is a useful NIHL phenotype for genetic association analyses. However, further research is necessary to reduce false-positive rates in notch identification.

Association of TagSNP in lncRNA HOTAIR with susceptibility to noise-induced hearing loss in a Chinese population.

BACKGROUND: Noise-induced hearing loss (NIHL) is a multifactorial disease, and dysregulation of oxidative stress is universally acknowledged as one crucial pathogenic factor for this disease. Recently studies have found the LncRNA HOTAIR is involved in the alteration of oxidative stress level, cell proliferation, cell cycle progression, and apoptosis. Considering the effects of lncRNA HOTAIR in cellular oxidative stress, we sought to investigate the influence of lncRNA HOTAIR variants on the risk of NIHL. METHODS: To explore the effects of HOTAIR polymorphisms on individual susceptibility to NIHL, We performed genotyping of three tagSNPs (rs874945, rs4759314 and rs7958904) in HOTAIR gene in a Chinese population which consists of 570 NIHL cases and 570 controls. The luciferase assays were further performed to investigate the regulatory function of HOTAIR tagSNPs. RESULTS: Our results revealed individuals with the G allele of HOTAIR tagSNP rs4759314 and the haplotype (rs874945, rs4759314 and rs7958904) are associated with an increased risk of NIHL in a Chinese population. Meanwhile, the rs4759314 G allele could significantly increase the expression of lncRNA HOTAIR. CONCLUSIONS: The genetic polymorphism within HOTAIR gene may play a crucial role in the occurrence and development of NIHL.

Estimated prevalence of hearing loss and provision of hearing services in Pacific Island nations.

INTRODUCTION: Hearing impairment (HI) affects an estimated 538 million people worldwide, with 80% of these living in developing countries. Untreated HI in childhood may lead to developmental delay and in adults results in social isolation, inability to find or maintain employment, and dependency. Early intervention and support programmes can significantly reduce the negative effects of HI. AIM: To estimate HI prevalence and identify available hearing services in some Pacific countries - Cook Islands, Fiji, Niue, Samoa, Tokelau, Tonga. METHODS: Data were collected through literature review and correspondence with service providers. Prevalence estimates were based on census data and previously published regional estimates. RESULTS: Estimates indicate 20-23% of the population may have at least a mild HI, with up to 11% having a moderate impairment or worse. Estimated incidence of chronic otitis media in Pacific Island nations is 3-5 times greater than other Australasian countries in children under 10 years old. Permanent HI from otitis media is substantially more likely in children and adults in Pacific Island nations. Several organisations and individuals provide some limited hearing services in a few Pacific Island nations, but the majority of people with HI are largely underserved. DISCUSSION: Although accurate information on HI prevalence is lacking, prevalence estimates of HI and ear disease suggest they are significant health conditions in Pacific Island nations. There is relatively little support for people with HI or ear disease in the Pacific region. An investment in initiatives to both identify and support people with hearing loss in the Pacific is necessary.

Noise and age-related hearing loss: a study of 40 123 gold miners in South Africa.

OBJECTIVE AND DESIGN: This retrospective cohort study aimed to describe the differential effect of noise exposure and age-related hearing loss in a large sample of gold miners in South Africa. STUDY SAMPLE: Audiological data of 40 123 South African mine workers were investigated. Data of a non-noise-exposed control group (n = 6162) and group exposed to underground noise (≥ 85 dB A (TWA) (n = 33 961) were included. Within these two larger noise-exposed groups two homogenous exposure groups (HEG) were also selected for analyses, namely the driller group (n = 4399) and the administration group (administrative workers) (n = 2211). Participants were categorized in terms of noise exposure, age, and race. RESULTS: Significantly different thresholds (worse for underground noise group) with respect to the median for all frequencies after adjusting for age was evident between the noise-exposed and control groups (ANCOVA). The largest differences in hearing thresholds between the noise-exposed and control groups were observed at 3 and 4 kHz in the age group 36 to 45 years. Administration and driller group differed significantly (driller group worse results) with respect to the mean LFA512 and HFA346 after adjusting for age (ANCOVA). Black males had significantly better high-frequency hearing compared with white male counterparts but significantly worse low-frequency hearing. CONCLUSION: Age was the most important influence on hearing thresholds for the noise and control groups. Race was shown to be a very significant factor determining susceptibility to NIHL and ARHL.

Portable music player users: cultural differences and potential dangers.

Many studies have examined the use of portable music players portable listening devices (PLDs) from various ethnic groups. Some findings suggest that there may be differences among ethnic groups that lead to louder or longer listening when using PLD devices. For example, some studies found that Hispanic PLD users listen at higher volume levels while other studies found that African American PLD users listen at higher volume levels. No investigator has explained the reasons for differences among ethnic groups in listening intensity. This paper will address the possible reasons for these differences and offer guidelines for the prevention of noise-induced hearing loss.

Noise exposure and hearing impairment among Chinese restaurant workers and entertainment employees in Hong Kong.

BACKGROUND: Noise-induced hearing loss (NIHL) is a major concern in the non-manufacturing industries. This study aimed to investigate the occupational noise exposure and the NIHL among Chinese restaurant workers and entertainment employees working in the service industry in Hong Kong. METHODS: This cross-sectional survey involved a total of 1,670 participants. Among them, 937 were randomly selected from the workers of Chinese restaurants and 733 were selected from workers in three entertainment sectors: radio and television stations; cultural performance halls or auditoria of the Leisure and Cultural Services Department (LCSD); and karaoke bars. Noise exposure levels were measured in the sampled restaurants and entertainment sectors. Each participant received an audiometric screening test. Those who were found to have abnormalities were required to take another diagnostic test in the health center. The "Klockhoff digit" method was used to classify NIHL in the present study. RESULTS: The main source of noise inside restaurants was the stoves. The mean hearing thresholds showed a typical dip at 3 to 6 KHz and a substantial proportion (23.7%) of the workers fulfilled the criteria for presumptive NIHL. For entertainment sectors, employees in radio and television stations generally had higher exposure levels than those in the halls or auditoria of the LCSD and karaoke bars. The mean hearing thresholds showed a typical dip at 6 KHz and a substantial proportion of the employees fulfilled the criteria for presumptive NIHL (38.6%, 95%CI: 35.1-42.1%). Being male, older, and having longer service and daily alcohol consumption were associated with noise-induced hearing impairment both in restaurant workers and entertainment employees. CONCLUSION: Excessive noise exposure is common in the Chinese restaurant and entertainment industries and a substantial proportion of restaurant workers and entertainment employees suffer from NIHL. Comprehensive hearing conservation programs should be introduced to the service industry in Hong Kong.

Lack of association between DNMT1 gene polymorphisms and noise-induced hearing loss in a Chinese population.

DNA methyltransferase 1 (DNMT1) plays a crucial role in maintaining of methylation and chromatin stability. And mutations in DNMT1 can induce one form of neurodegenerative diseases with dementia and sensorineural hearing loss. To assess whether single nucleotide polymorphisms (SNPs) or haplotypes of DNMT1 are related to noise-induced hearing loss (NIHL) in a Chinese population, we genotyped three functional polymorphisms (rs12984523, rs16999593, and rs2228612) in a case-control study involving 615 NIHL cases and 644 controls. However, no significant association was detected between these three SNPs and NIHL susceptibility in the Chinese population. Our data suggested that the DNMT1 polymorphisms may not contribute to risk of NIHL in the Chinese population.

Noise perception in the workplace and auditory and extra-auditory symptoms referred by university professors.

PURPOSE: To investigate the correlation between noise in the work environment and auditory and extra-auditory symptoms referred by university professors. METHODS: Eighty five professors answered a questionnaire about identification, functional status, and health. The relationship between occupational noise and auditory and extra-auditory symptoms was investigated. Statistical analysis considered the significance level of 5%. RESULTS: None of the professors indicated absence of noise. Responses were grouped in Always (A) (n=21) and Not Always (NA) (n=63). Significant sources of noise were both the yard and another class, which were classified as high intensity; poor acoustic and echo. There was no association between referred noise and health complaints, such as digestive, hormonal, osteoarticular, dental, circulatory, respiratory and emotional complaints. There was also no association between referred noise and hearing complaints, and the group A showed higher occurrence of responses regarding noise nuisance, hearing difficulty and dizziness/vertigo, tinnitus, and earache. There was association between referred noise and voice alterations, and the group NA presented higher percentage of cases with voice alterations than the group A. CONCLUSION: The university environment was considered noisy; however, there was no association with auditory and extra-auditory symptoms. The hearing complaints were more evident among professors in the group A. Professors' health is a multi-dimensional product and, therefore, noise cannot be considered the only aggravation factor.

Percepção de ruído no ambiente de trabalho e sintomas auditivos e extra-auditivos autorreferidos por professores universitários / Noise perception in the workplace and auditory and extra-auditory symptoms referred by university professors

OBJETIVO: Investigar a correlação entre ruído no ambiente de trabalho e sintomas auditivos e extra-auditivos mencionados por professores universitários. MÉTODOS: Oitenta e quatro professores responderam a um questionário com questões sobre identificação, situação funcional e saúde. A relação entre ruído no trabalho e sintomas extra-auditivos e auditivos foi pesquisada. Foi realizada análise estatística, considerando o nível de significância de 5%. RESULTADOS: Nenhum professor indicou ausência de ruído. As respostas foram agrupadas em Sempre (S) (n=21) e Não Sempre (NS) (n=63). Houve diferença quanto ao pátio e a outra sala de aula como fontes de ruído, classificado como de forte intensidade; acústica insatisfatória e eco. Não houve associação entre referência à presença de ruído e queixas extra-auditivas do tipo digestivo, hormonal, osteoarticular, dentário, circulatório, emocional e respiratório. Não houve associação entre autopercepção de presença de ruído e de queixas auditivas e o grupo S mostrou maior ocorrência de respostas em incômodo ao ruído, dificuldade de ouvir e tontura/vertigem, zumbido e dor de ouvido. Houve associação entre autopercepção de alterações na voz e ruído e o grupo NS apresentou maior porcentagem de casos com alteração na voz que o grupo S. CONCLUSÃO: O ambiente universitário foi considerado ruidoso, porém não houve associação com doenças extra-auditivas e auditivas. As queixas auditivas foram mais evidentes naqueles professores que referiram ruído na modalidade Sempre. A saúde dos docentes é produto multidimensional, desta forma, o ruído não pode ser considerado fator único de agravo.

PURPOSE: To investigate the correlation between noise in the work environment and auditory and extra-auditory symptoms referred by university professors. METHODS: Eighty five professors answered a questionnaire about identification, functional status, and health. The relationship between occupational noise and auditory and extra-auditory symptoms was investigated. Statistical analysis considered the significance level of 5%. RESULTS: None of the professors indicated absence of noise. Responses were grouped in Always (A) (n=21) and Not Always (NA) (n=63). Significant sources of noise were both the yard and another class, which were classified as high intensity; poor acoustic and echo. There was no association between referred noise and health complaints, such as digestive, hormonal, osteoarticular, dental, circulatory, respiratory and emotional complaints. There was also no association between referred noise and hearing complaints, and the group A showed higher occurrence of responses regarding noise nuisance, hearing difficulty and dizziness/vertigo, tinnitus, and earache. There was association between referred noise and voice alterations, and the group NA presented higher percentage of cases with voice alterations than the group A. CONCLUSION: The university environment was considered noisy; however, there was no association with auditory and extra-auditory symptoms. The hearing complaints were more evident among professors in the group A. Professors' health is a multi-dimensional product and, therefore, noise cannot be considered the only aggravation factor.

Factors affecting Thai workers' use of hearing protection.

This study used an ecological model to examine Thai workers' beliefs and attitudes toward using occupational hearing protection. Data collection involved focus group sessions with 28 noise-exposed workers at four factories in Chiang Mai Province and an interview with a safety officer at each organization. Detailed content analysis resulted in the identification of three types of factors influencing the use of hearing protection: intrapersonal, including preventing impaired hearing, noise annoyance, personal discomfort, and interference with communication; interpersonal, including coworker modeling, supervisor support, and supervisor modeling; and organizational, including organizational rules and regulations, provision of hearing protection devices, dissemination of knowledge and information, noise monitoring, and hearing testing. Effective hearing protection programs depend on knowledge of all of these factors. Strategies to promote workers' use of hearing protection should include the complete range of factors having the potential to affect workers' hearing.

Young adults' use and output level settings of personal music systems.

OBJECTIVES: There are growing concerns over noise exposure via personal music system use by young adults. One purpose of this study was to evaluate the prevalence of personal music system use and the listening patterns associated with these systems in a large sample of young adults. A second purpose of this study was to measure the dB SPL in the ear canal of young adults while they blindly set the volume of a personal music system to four settings. DESIGN: In the first study, the personal music system use survey was completed by 1016 students at various locations on the San Diego State University campus. Questions included sex, age, ethnicity, race, and whether or not they used a personal music system. Students who answered Yes to using a personal music system were instructed to complete the remaining 11 closed-set questions. These questions dealt with type of earphones used with the system, most common listening environment, length of time per day the system was used, and the volume setting. The differences between women and men and across ethnicity and race were evaluated for the questions. In the second study, a probe microphone placed in the ear canal of 32 participants was used to determine the dB SPL of four loudness categories at which the participants blindly set the level of a personal music system: low, medium or comfortable, loud, and very loud. RESULTS: In study 1, over 90% of the participants who completed the survey reported using a personal music system. Over 50% of those who use a personal music system reported listening between 1 and 3 hrs and almost 90% reported listening at either a medium or loud volume. Men were significantly more likely to report listening to their system for a longer duration compared with women and more likely to report listening at a very loud volume. There was a trend for Hispanic or Latino students to report listening for longer durations compared with Not Hispanic or Latino students, but this difference was not statistically significant. Black or African American students were significantly more likely to report listening to their personal music system between 3 and 5 hrs and more than 5 hrs and to report listening at a very loud volume compared with other racial groups. In study 2, the mean dB SPL values for low, medium or comfortable, loud, and very loud were 62.0, 71.6, 87.7, and 97.8 dB SPL, respectively. Men set the level of very loud significantly higher than women. CONCLUSIONS: It is clear that a vast majority of young adults who completed the personal music system use survey listen to a system using earphones. Most of the respondents listen between 1 and 3 hrs a day at a medium or loud volume. Based on the probe microphone measurement results, the volume settings for reported durations may not be hazardous for hearing. Long-term use of personal music systems, however, in combination with other noise exposures (i.e., recreational, occupational), and their effect on hearing remains a question for additional research.

Noise and hearing protection: Latino construction workers' experiences.

This study explored Latino construction workers' experiences with occupational noise and hearing protection to provide qualitative data to be used in designing an intervention to prevent noise-induced hearing loss. An ecological framework provided the theoretical foundation for this study. Fifteen Latino construction workers participated in one of four focus groups exploring perceptions of exposure to noise on the job and barriers to and supports for wearing hearing protection. Support for an ecological framework was apparent in the environmental and personal factors revealed in the data: how it feels, personal responsibility, they make us wear it, we don't care about ears, it won't happen to me, being Latino, keeping our jobs, hearing protection is uncomfortable, and we can handle it. Researchers are applying results of this study in the development of a hearing conservation intervention for Latino construction workers to be evaluated in a randomized, controlled trial.

Knowledge, behaviors, and attitudes about hearing loss and hearing protection among racial/ethnically diverse young adults.

Over 11 million individuals exhibit some degree of permanent noise induced hearing loss (NIHL). Despite such data, there remains a paucity of empirical evidence on the knowledge of noise exposure and hearing protection devices (HPDs) for young adults, particularly those of diverse racial/ethnic backgrounds. This lack of research is unfortunate, as prior research suggests that the incidence of NIHL can be reduced through educational programs, such as hearing conservation programs (HCPs). Moreover, research also indicates that such educational programs are more beneficial when developed for specific age and/or ethnic/racial groups. The primary aim of this investigation was to determine the knowledge base of 200 college-aged young adults aged 18-29, concerning the auditory mechanism, NIHL, and the use of HPDs. The second aim of this study was to identify race and ethnicity differences or similarities in knowledge of these areas among African-American and caucasian young adults. Overall, in many instances, a majority of the young adults in our study demonstrated a high degree of knowledge concerning factors associated with exposure to excessive noise and the risk of hearing loss. Yet, the results also revealed significant racial/ethnic differences in knowledge, behaviors, and attitudes about the use of HPDs. Recent estimates suggest that more than 11 million individuals in the United States exhibit some degree of NIHL. Moreover, 40 million individuals work in environments that contain potentially harmful noise levels, and over 50 million Americans routinely use firearms--a common cause of noise-induced hearing impairment. A specific hallmark manifestation of NIHL is a permanent decrease in hearing sensitivity from 3,000-6,000 Hz, with a characteristic notch at 4,000 Hz. Additional effects of exposure to high noise levels include physiological changes in heart rate and blood pressure, decrease in work productivity, and an interference with communication that results from the masking of speech. With these considerations in mind, the purpose of this study was to investigate the knowledge, behaviors, and attitudes of a young-adult population in the United States concerning the factors that contribute to NIHL and the use of hearing protection. Additionally, this study was interested in whether there were racial/ethnic differences or similarities in knowledge of hearing loss and the use of HPDs among African-American and caucasian young adults.

Explaining Mexican American workers' hearing protection use with the health promotion model.

BACKGROUND: Mexican American workers are vulnerable to noise-induced hearing loss, the most common occupational disease in the United States. OBJECTIVES: The purpose was to test the applicability of the Health Promotion Model to Mexican American workers' use of hearing protection devices. METHOD: A correlational descriptive design and path analysis were used to determine the relationships between cognitive-perceptual factors, modifying factors and use of hearing protection devices. A questionnaire was completed by a total of 119 workers in three garment manufacturing plants. Interviews were conducted with the occupational health nurse or safety director in each plant to determine the policy regarding hearing protection also. RESULTS: Factors that directly influenced the use of hearing protection devices were a clinical definition of health, benefits of and barriers to use of hearing protection devices, self-efficacy in the use of hearing protection devices and perceived health status (R2 =.25, p <.01). An exploratory analysis allowing a direct relationship of modifying factors with the dependent variable explained additional variance in use of hearing protection devices through the contribution of situational factors (R2 =.55, p <.01). CONCLUSIONS: Important factors related to Mexican American workers' use of hearing protection devices were identified to provide direction for nursing interventions. Future research should further test the explanatory capabilities of the Health Promotion Model, explore the importance of situational influences on health behavior, and ensure reliable measures of all model components for this population.

Is acculturation related to use of hearing protection?

Noise-exposed employees with limited English skills may pose a special challenge for hearing conservation programs. This pilot field study assessed knowledge, attitudes, and behavior regarding use of hearing protective devices in a largely Hispanic group of 88 workers exposed to industrial noise. Effectiveness of hearing protection was determined through field measurements of personal attenuation ratings. Individual scores on an acculturation scale (first language learned, language at home, degree of literacy in English, preferred language) demonstrated a correlation between a low degree of acculturation and low personal attenuation rating (R2= 0.49, p=0.0001). Low acculturation was also correlated with high-perceived barriers to use of hearing protection (p=0.006). Although neither self reports of self-efficacy nor perceived benefits of hearing protection correlated with personal attenuation rating, perceived barriers to hearing protector use was a significant predictor of hearing protector fit (p=0.05). These results indicate that less acculturated workers may be underutilizing hearing protection in the workplace partly due to perceived barriers to use of hearing protective devices. To be effective, hearing conservation training programs in work sites with an immigrant work force need to address language and cultural barriers to the use of hearing protection.

Estimated prevalence of noise-induced hearing threshold shifts among children 6 to 19 years of age: the Third National Health and Nutrition Examination Survey, 1988-1994, United States.

OBJECTIVE: This analysis estimates the first nationally representative prevalence of noise-induced hearing threshold shifts (NITS) among US children. Historically, NITS has not been considered a common cause of childhood hearing problems. Among children, NITS can be a progressive problem with continued exposure to excessive noise, which can lead to high-frequency sound discrimination difficulties (eg, speech consonants and whistles). METHODS: The Third National Health and Nutrition Examination Survey (NHANES III) was conducted from 1988 to 1994. NHANES III is a national population-based cross-sectional survey with a household interview, audiometric testing at 0.5 to 8 kHz, and compliance testing. A total of 5249 children aged 6 to 19 years completed audiometry and compliance testing for both ears in NHANES III. The criteria used to assess NITS included audiometry indicating a noise notch in at least 1 ear. RESULTS: Of US children 6 to 19 years old, 12.5% (approximately 5.2 million) are estimated to have NITS in 1 or both ears. In the majority of the children meeting NITS criteria, only 1 ear and only 1 frequency are affected. In this analysis, all children identified with NITS passed compliance testing, which essentially rules out middle ear disorders such as conductive hearing loss. The prevalence estimate of NITS differed by sociodemographics, including age and sex. CONCLUSIONS: These findings suggest that children are being exposed to excessive amounts of hazardous levels of noise, and children's hearing is vulnerable to these exposures. These data support the need for research on appropriate hearing conservation methods and for NITS screening programs among school-aged children. Public health interventions such as education, training, audiometric testing, exposure assessment, hearing protection, and noise control when feasible are all components of occupational hearing conservation that could be adapted to children's needs with children-specific research.

Race/ethnicity differences in the prevalence of noise-induced hearing loss in a group of metal fabricating workers.

The National Institute of Occupational Safety and Health rates noise-induced hearing loss as one of the top 10 work-related problems, involving at least 11 million workers. This retrospective study examines the differences between pure-tone hearing loss and race/ethnicity in 216 white and 70 non-white male metal fabricating workers. Significant variables upon univariate analysis found to be associated with race/ethnicity were mean years of employment and proportion of time worked without hearing protection. Among whites, the permanent threshold average for 1, 2, 3 and 5 kHz was 25.99 dB, compared with 17.71 dB in non-whites (P < 0.01). Backwards stepwise regression indicated that race/ethnicity, after being adjusted for years of employment, was the major-effect variable. The results of this study suggest that occupational noise exposure alone does not alone account for the racial hearing differences.

Identifying comparison groups for evaluating occupational hearing loss: a statistical assessment of 22 industrial populations.

Finding appropriate comparison groups to study occupational hearing loss has been difficult. Recently, however, the National Institute for Occupational Safety and Health sponsored the complication of potentially useful data from 22 diverse industrial companies in the U.S.A. and Canada. We conducted a statistical evaluation to determine which of the 22 populations might be suited as comparison groups in future studies of workers exposed to hazardous noise. In a Cox Proportional Hazards model that included age and sex, the relative risk of developing hearing loss in each company was estimated at two, five, and ten years of follow-up. We ranked the companies based on their relative risks, and rated them on a five-point scale from "excellent" to "poor" to indicate their suitability as comparison groups. The risk profiles developed and other variables described in this study will assist researchers in selecting appropriate comparison groups for evaluating occupational hearing loss.

Noise-induced hearing loss, nationality, and blood pressure.

Noise exposure has been associated with increased catecholamine production and blood pressure elevation in laboratory studies and in human volunteers. Epidemiologic studies have given conflicting results. In order to determine whether noise-induced hearing loss predicts a rise in blood pressure, we reviewed occupational medicine records in an occupational health center serving three companies where noise exposure is commonly found. Height, weight, blood pressure, and screening audiometry are obtained as part of routine occupational health screening, and the results of the screening visit are abstracted from written clinical records. The results of pure tone screening audiometry are reported in nonstandardized fashion (Normal, WNL, NAD, for example, for normal). We reviewed records from 1990 and 1991 inclusive. One investigator, blind to blood pressure status, assigned each record to "no hearing loss," "not codable," or "hearing loss assumed to be due to noise" on the basis of the written audiometry report. Hearing loss due to causes other than noise was considered not codable. No attempt was made to quantify severity of hearing loss. Two hundred and sixteen charts were excluded as "not codable," 1,535 were classified as having no hearing loss, and 610 had some degree of hearing loss, most probably due to noise exposure. To adjust for confounding covariates, multiple regression analysis was used and indicated that hearing status improves the regression model for predicting diastolic blood pressure (p = 0.04), following age, nationality, body mass index (BMI), and month of testing, although the effect is small. Stratification by age and BMI revealed increased diastolic pressure in the group with hearing loss under age 45, regardless of obesity.(ABSTRACT TRUNCATED AT 250 WORDS)