Occupational noise, smoking, and a high body mass index are risk factors for age-related hearing impairment and moderate alcohol consumption is protective: a European population-based multicenter study

Impulse noise exposure in early adulthood accelerates age-related hearing loss

The aim of this study was to investigate the influence of impulse noise on age-related hearing loss. The study consisted of two groups. Each group contained 109 men. Group I comprised veterans with normal hearing at the end of 1979 sino-vietnamese war. All these veterans were randomly selected from Guangzhou Military Command. Group II were men with no military experience randomly chosen from the health examination center of Guangzhou General Hospital of Guangzhou Military Command. Pure-tone thresholds of these two groups were measured and compared. The pure-tone thresholds of Group I were poorer than those of Group II at the frequencies of 4, 6 and 8 kHz. Thus, impulse noise accelerates age-related hearing loss.

Relationship of cigarette smoking and hearing loss in workers exposed to occupational noise

Objectives

To investigate the effects of smoking on hearing loss among workers exposed to occupational noise.

Methods

From the results of a special workers health examination performed in 2011, we enrolled 8,543 subjects exposed to occupational noise and reviewed the findings. Using self-reported questionnaires and health examination results, we collected data on age, smoking status, disease status, height, weight, and biochemistry and pure tone audiometry findings. We divided the workers into 3 groups according to smoking status (non-smoker, ex-smoker, current smoker). Current smokers (n = 3,593) were divided into 4 groups according to smoking amount (0.05–9.9, 10–19.9, 20–29.9, ≥30 pack-years). We analyzed the data to compare hearing thresholds between smoking statuses using analysis of covariance (ANCOVA) after controlling for confounder effects.

Results

According to ANCOVA, the hearing thresholds of current smokers at 2 k, 3 k, and 4 kHz were significantly higher than that of the other groups. Multiple logistic regression for smoking status (reference: non-smokers) showed that the adjusted odds ratios of current smokers were 1.291 (95% confidence interval [CI]: 1.055–1.580), 1.180 (95% CI: 1.007–1.383), 1.295 (95% CI: 1.125–1.491), and 1.321 (95% CI: 1.157–1.507) at 1 k, 2 k, 3 k, and 4 kHz, respectively. Based on smoking amount, the adjusted odds ratios were 1.562 (95% CI: 1.013–2.408) and 1.643 (95% CI: 1.023–2.640) for the 10–19.9 and ≥30 pack-years group, respectively, at 1 kHz (reference: 0.05–9.9 pack-years). At 2 kHz, the adjusted odds ratios were increased statistically significantly with smoking amount for all groups. At all frequencies tested, the hearing thresholds of noise-exposed workers were significantly influenced by current smoking, in particular, the increase of hearing loss at low frequencies according to smoking amount was more prevalent.

Conclusions

Current smoking significantly influenced hearing loss at all frequencies in workers exposed to occupational noise, and heavier smoking influenced low-frequency hearing loss more greatly. There was a dose–response relationship between smoking amount and low-frequency hearing thresholds; however, this was not observed for high-frequency hearing thresholds. Therefore, well-designed prospective studies are needed to clarify the effects of smoking on the degree of hearing loss.

Obesity is associated with sensorineural hearing loss in adolescents

OBJECTIVES/HYPOTHESIS

Childhood obesity, defined as body mass index (BMI) ≥ 95%, is a significant health problem associated with a variety of disorders, and in adults it has been found to be a risk factor for hearing loss. We investigated the hypothesis that obese children are at increased risk of sensorineural hearing loss (SNHL).

STUDY DESIGN

A complex, multistage, stratified geographic area design for collecting representative data from noninstitutionalized U.S. population.

METHODS

Relevant cross-sectional data from the National Health and Nutrition Examination Survey, 2005 to 2006, for 1,488 participants 12 to 19 years of age was examined. Subjects were classified as obese if their BMI ≥ 95 th percentile. SNHL was defined as average pure-tone level greater than 15 dB for 0.5, 1, and 2 kHz (low frequency) and 3, 4, 6, and 8 kHz (high frequency).

RESULTS

Compared to normal weight participants (BMI 5%-85%), obesity in adolescents was associated with elevated pure tone hearing thresholds and greater prevalence of unilateral low-frequency SNHL (15.2 vs. 8.3%, P = 0.01). In multivariate analyses, obesity was associated with a 1.85 fold increase in the odds of unilateral low-frequency SNHL (95% CI: 1.10-3.13) after controlling for multiple hearing-related covariates.

CONCLUSIONS

We demonstrate for the first time that obesity in childhood is associated with higher hearing thresholds across all frequencies and an almost 2-fold increase in the odds of unilateral low-frequency hearing loss. These results add to the growing literature on obesity-related health disturbances and also add to the urgency in instituting public health measures to reduce it.

Geriatric syndromes--vascular disorders?

The term geriatric syndrome is used to characterize multifactorial clinical conditions among older people which are not subsumed readily into disease entities, but which nevertheless predispose older people to disability and death. Commonly included are frailty, dementia, delirium, incontinence, falls, and dizziness. Geriatric syndromes are common among older people: in a recent survey, 50% of those aged more than 65 had one or more of these conditions. Better methods for prevention and treatment are needed, but current strategies have lacked a coherent conceptual and diagnostic framework. Prevention and interventions need to be targeted at earlier ages, with geriatrics expertise needed in the definition and operationalization of these complex entities. In this review we consolidate evidence that vascular disorders, including vascular ageing and vascular diseases, are key etiological factors of geriatric syndromes. Identifying this vascular dimension would offer opportunities for more efficient preventive strategies and mandates earlier intervention, especially for women, among whom vascular disease is often expressed more insidiously than among men. This would entail a sensitization of the health care system to the systematic detection of the syndromes, which are currently underdiagnosed. Further disentangling of the mechanisms of vascular ageing may offer therapies for vascular diseases and geriatric syndromes alike.

Diet-induced obesity exacerbates auditory degeneration via hypoxia, inflammation, and apoptosis signaling pathways in CD/1 mice

The aim of this study was to investigate the mechanisms of diet-induced obesity on hearing degeneration in CD/1 mice. Sixty 4-week-old male CD/1 mice were randomly and equally divided into 2 groups. For 16 weeks, the diet-induced obesity (DIO) group was fed a high fat diet and the control group was fed a standard diet of 13.43 % kcal fat. The morphometry, biochemistry, auditory brainstem response thresholds, omental fat, and histopathology of the cochlea were compared between the beginning and end of the study (4 vs. 20 weeks old). The results show that the body weight, fasting plasma triglyceride concentrations, and omental fat weight were higher in the DIO group than in the control group at the end of experiment. The auditory brainstem response thresholds at high frequencies were significantly elevated in the DIO group compared to those of the control group. Histology studies showed that, compared to the control group, the DIO group had blood vessels with smaller diameters and thicker walls in the stria vascularis at the middle and basal turns of the cochlea. The cell densities in the spiral ganglion and spiral ligament at the basal turn of the cochlea were significantly lower in the DIO group. Immunohistochemical staining showed that hypoxia-induced factor 1 (HIF-1), tumor necrosis factor alpha (TNF-α), nuclear factor kappa B (NF-κB), caspase 3, poly(ADP-ribose) polymerase-1, and apoptosis inducing factor were all significantly more dense in the spiral ganglion and spiral ligament at the basal turn of cochlea in the DIO group. Our results suggest that diet-induced obesity exacerbates hearing degeneration via increased hypoxia, inflammatory responses, and cell loss in the spiral ganglion and spiral ligament and is associated with the activation of both caspase-dependent and -independent apoptosis signaling pathways in CD/1 mice.

Occupational noise-induced hearing loss in Indian steel industry workers: an exploratory study

OBJECTIVE

The present study focused on exploring the current level of hearing protection and subsequently determined the prevalence of occupational noise-induced hearing loss among casting and forging industry workers.

BACKGROUND

The casting and forging industry provides employment to a significant portion of the population.

METHOD

The level of hearing protection was assessed through questionnaire survey of 572 workers. Out of these workers, 165 and another control group of 57 participants were assessed by formal audiometry. Audiometric tests were conducted at frequencies of 1.0 KHz to 8.0 KHz.The occurrence of hearing loss was determined on the basis of a hearing threshold level with a low fence of 25 dB. Student's test and ANOVA were used to compare the various groups; a p value < .05 was considered statistically significant.

RESULTS

More than 90% of the workers sampled showed significant hearing loss at medium and high frequencies. The analyses revealed a higher prevalence of significant hearing loss among the forging workers compared with the workers associated with the other activities.

CONCLUSIONS

The workers of the Indian steel industry are highly exposed to occupational noise. The majority of workers are not protected from noise-induced hearing loss. There is a need to provide special ear protectors for workers engaged in forging. A complete hearing protection program, including training, audiometry, job rotation, and the use of hearing protection devices, needs to be introduced.

Trajectories of older adults' hearing difficulties: examining the influence of health behaviors and social activity over 10 years

AIM

The aims of the present study were to describe the trajectories of self-reported hearing difficulties over time, and evaluate the impacts of age, sex, lifestyle factors and social activity, in explaining individual differences in patterns of change over time.

METHODS

As part of the Melbourne Longitudinal Studies on Healthy Aging (MELSHA) Program, the hearing status of 947 adults aged 65 years and older, across five measurement periods (over 10 years), were analyzed using Latent Growth Curve Modeling analysis. A multidimensional survey was also administered, which included questions relating to sociodemographic variables, self-reported hearing difficulties, nutrition, smoking habits and level of social activity.

RESULTS

Although there was a general increase in hearing difficulties over time, older age, poor nutrition, a lifetime of smoking and increased social activity predicted more rapid increases in hearing difficulty over time.

CONCLUSIONS

Findings support the importance of lifestyle factors in reducing the rate of perceived hearing difficulties in older people, and provide further evidence of the links between lifestyle and sensory loss in older people. Poor nutrition and smoking are areas that both clinicians and public health professionals should address in their work with older people.

Intake of specific nutrients and foods and hearing level measured 13 years later

Only a few studies have investigated the impact of nutrients and food groups on hearing level (HL) with a population-based approach. We examined the 13-year association between intake of specific nutrients and food groups and HL in a sample of French adults. A total of 1823 subjects, aged 45-60 years at baseline, participating in the Supplementation with Antioxidant Vitamins and Minerals 2 cohort were selected. Nutrient and food intake was estimated at baseline among participants who had completed at least six 24 h dietary records. HL was assessed 13 years after baseline and was defined as the pure-tone air conduction of the worse ear at the following thresholds: 0·5, 1, 2 and 4 kHz. The relationship between quartiles of energy-adjusted nutrient and food intake and HL was assessed by multivariate linear regression analyses, in men and women separately. Intakes of retinol (P-trend ¼ 0·058) and vitamin B12 (P-trend=0·068) tended to be associated with better HL in women. Intakes of meat as a whole (P-trend=0·030), red meat (P-trend=0·014) and organ meat (P-trend=0·017) were associated with better HL in women. Higher intake of seafood as a whole (P-trend=0·07) and of shellfish (P-trend=0·097) tended to be associated with better HL in men. Consumption of meat is therefore associated with a better HL in women. Further research is required to better elucidate the mechanisms behind the associations between diet and hearing.

Waist circumference is associated with pitch pattern sequence score in older male adults

OBJECTIVE

While obesity may increase the risk for neurodegenerative diseases such as Alzheimer's disease, the relationship between waist circumference (WC) and central auditory dysfunction is unknown. We aimed to investigate the relationship of WC and pitch pattern sequence (PPS) score in adults.

DESIGN

The association of WC with PPS score was analysed.

STUDY SAMPLE

Volunteer helpers at a community hospital, 391 adults ≥40 years, with normal or symmetrical sensorineural hearing loss were randomly selected.

RESULTS

After adjusting for age, gender, pure-tone average, systemic diseases, and habits, WC was significantly negatively associated with PPS. In a subgroup analysis by gender and age, the PPS score was negatively associated with WC only for males who were older than 55 years old, but not for males who were younger than 55 years old or females in either age group. Meanwhile, central obesity showed positive association with abnormal PPS recognition ability (PPS score < 90%) of borderline significance only for males who were older than 55 years old, but not for males who were younger than 55 years old or females in both age groups.

CONCLUSIONS

WC or central obesity is an independent risk factor for poor central auditory function, especially in older male subjects.

Prevalence and risk factors of hearing loss using the korean working conditions survey

Background and Objectives

The hearing loss of workers can occur when they are affected by age, otologic disease, and work-related risks such as noise and chemicals. Based on the Korean Working Conditions Survey (KWCS) in 2010, this research aimed to estimate the prevalence rate of hearing loss and to identify the risk factors affecting its occurrence.

Subjects and Methods

The subjects were 10019 employees who completed an interview conducted as part of KWCS in 2010. The prevalence rate of hearing loss according to sex, age, education, income, smoking, drinking, hypertension, industrial type, occupations, employment status, working period, and hazards at the workplace were assessed. The factors that could affect the occurrence of hearing loss were investigated based on a logistic regression analysis.

Results

The prevalence rate of hearing loss was 2.7%. In a logistic multivariate analysis, sex, age, occupations, working period, noise, and exposure to chemicals showed statistically significant correlations to the occurrence of hearing loss. The adjusted odd ratios were as follows: 1.74 [95% confidence interval (CI), 1.03-2.96] for males, 2.11 (95% CI, 1.14-3.89) for those in their 40s, 2.24 (95% CI, 1.19-4.20) for those in their 50s, 2.21 (95% CI, 1.18-4.15) for manage/professional works, 2.73 (95% CI, 1.69-4.41) for manufacturing, 2.07 (95% CI, 1.36-3.15) for those who have worked for more than 20 years, 1.72 (95% CI, 1.14-2.58) for noise exposure, 1.53 (95% CI, 1.02-2.30) for vibration exposure and 1.58 (95% CI, 1.11-2.24) for chemical exposure.

Conclusions

The overall occupational and non-occupational risk factors related to employees' hearing loss were reviewed. In addition to the exposure to noise, occupational risks of hearing loss, such as isolated exposure to vibration and chemicals, and combined exposure to noise and these hazards, were identified. Multiple exposure to hazards, along with prolonged noise exposure increased the risk of hearing loss.

Ear diseases and other risk factors for hearing impairment among adults: an epidemiological study

OBJECTIVE

To investigate the prevalence of ear diseases, other otological risk factors potentially affecting hearing, and noise exposure among adults. Furthermore, subject-related factors possibly associated with hearing impairment (HI), i.e. handedness, eye color, and susceptibility to sunburn, were studied.

DESIGN

A cross-sectional, unscreened, population-based, epidemiological study among adults.

STUDY SAMPLE

The subjects (n = 850), aged 54-66 years, were randomly sampled from the population register. A questionnaire survey, an otological examination, and pure-tone audiometry were performed.

RESULTS

Chronic middle-ear disease (both active and inactive) was the most common ear disease with a prevalence of 5.3%, while the prevalence of otosclerosis was 1.3%, and that of Ménière's disease, 0.7%. Noise exposure was reported by 46% of the subjects, and it had no effect on hearing among those with no ear disease or other otological risk factors for HI. Dark eye color and non-susceptibility to sunburn were associated with HI among noise-exposed subjects.

CONCLUSIONS

Common ear diseases and other otological risk factors constitute a major part of the etiologies of HI among adults. Contrary to previous studies, noise exposure turned out to have only marginal effect on hearing among those with no otological risk factors.

Hearing ability with age in northern European women: a new web-based approach to genetic studies

Age-related hearing impairment (ARHI) affects 25–40% of individuals over the age of 65. Despite the high prevalence of this complex trait, ARHI is still poorly understood. We hypothesized that variance in hearing ability with age is largely determined by genetic factors. We collected audiologic data on females of Northern European ancestry and compared different audiogram representations. A web-based speech-to-noise ratio (SNR) hearing test was compared with pure-tone thresholds to see if we could determine accurately hearing ability on people at home and the genetic contribution to each trait compared. Volunteers were recruited from the TwinsUK cohort. Hearing ability was determined using pure-tone audiometry and a web-based hearing test. Different audiogram presentations were compared for age-correlation and reflection of audiogram shape. Using structural equation modelling based on the classical twin model the heritability of ARHI, as measured by the different phenotypes, was estimated and shared variance between the web-based SNR test and pure-tone audiometry determined using bivariate modelling. Pure-tone audiometric data was collected on 1033 older females (age: 41–86). 1970 volunteers (males and females, age: 18–85) participated in the SNR. In the comparison between different ARHI phenotypes the difference between the first two principle components (PC1–PC2) best represented ARHI. The SNR test showed a sensitivity and specificity of 89% and 80%, respectively, in comparison with pure-tone audiogram data. Univariate heritability estimates ranged from 0.70 (95% CI: 0.63–0.76) for (PC1–PC2) to 0.56 (95% CI: 0.48–0.63) for PC2. The genetic correlation of PC1–PC2 and SNR was −0.67 showing that the 2 traits share variances attributed to additive genetic factors. Hearing ability showed considerable heritability in our sample. We have shown that the SNR test provides a useful surrogate marker of hearing. This will enable a much larger sample to be collected at a fraction of the cost, facilitating future genetic association studies.

Markers of inflammatory status are associated with hearing threshold in older people: findings from the Hertfordshire Ageing Study

BACKGROUND

Age-related hearing loss is a common disabling condition but its causes are not well understood and the role of inflammation as an influencing factor has received little consideration in the literature.

OBJECTIVE

To investigate the association between inflammatory markers and hearing in community-dwelling older men and women.

DESIGN

Cross-sectional analysis within a cohort study.

SETTING

The Hertfordshire Ageing Study.

PARTICIPANTS

A total of 343 men and 268 women aged 63-74 years on whom data on audiometric testing, inflammatory markers and covariates were available at follow-up in 1995.

MAIN OUTCOME MEASURES

Average hearing threshold level (across 500-4,000 Hz) of the worst hearing ear and audiometric slope in dB/octave from 500 to 4,000 Hz.

RESULTS

Older age, smoking, history of noise exposure and male gender (all P < 0.001) were associated with higher mean hearing threshold in the worse ear in univariate analysis. After adjustment for these factors in multiple regression models, four measures of immune or inflammatory status were significantly associated with hearing threshold, namely white blood cell count (r = 0.13, P = 0.001), neutrophil count (r = 0.13, P = 0.002), IL-6 (r = 0.10, P = 0.05) and C-reactive protein (r = 0.11, P = 0.01). None of the inflammatory markers was associated with maximum audiometric slope in adjusted analyses.

CONCLUSIONS

Markers of inflammatory status were significantly associated with degree of hearing loss in older people. The findings are consistent with the possibility that inflammatory changes occurring with ageing may be involved in age-related hearing loss. Longitudinal data would enable this hypothesis to be explored further.

Effects of cigarette smoking on hearing recovery from noise-induced temporary hearing threshold shifts in mice

HYPOTHESIS

Cigarette smoking may potentiate noise-induced hearing loss.

BACKGROUND

Many epidemiological studies have shown that cigarette smoking is a major risk factor for noise-induced hearing loss.

METHODS

BALB/c mice were exposed to passive smoking for 2 h/d for 2 weeks before exposure to 110-dB sound pressure level white noise for 3 hours once. Hearing was assessed via the auditory brainstem response with tone-burst stimulation and distortion product otoacoustic emissions before and at 1, 3, 5, 7, 14, 21, and 28 days after noise exposure. Oxidative stress and hypoxia were assessed by immunostaining with 8-oxoG and hypoxia-inducible factor 1α, respectively.

RESULTS

Control mice unexposed to both smoking and noise and mice exposed to smoking only showed no shift in hearing threshold. In contrast, mice exposed to noise only or smoking plus noise showed abrupt increases in hearing threshold. In mice exposed to noise only, hearing threshold returned to prenoise levels after 2 weeks. However, in mice exposed to smoking plus noise, the loss of hearing was significantly higher, and hearing threshold did not return to the pre-exposure levels until 4 weeks later. Positive staining with 8-oxoG and hypoxia-inducible factor 1α were observed in the inner ear of the smoking-only and smoking-plus-noise group similar to noise-only mice, whereas no positive staining was observed in control group.

CONCLUSION

These results indicate that cigarette smoking may potentiate the harmful effects of noise on hearing and disturb the recovery mechanism in the cochlea.

Association of plasma adiponectin levels with hearing thresholds in adults

OBJECTIVE

Obesity is an independent risk factor for age-related hearing impairment. Adiponectin is one of the major adipocytokines secreted by adipose tissue. The aim of our study was to examine whether there is an association between plasma adiponectin concentrations and hearing sensitivity in adults.

DESIGN AND METHODS

We recruited 954 adults aged 40-86 years, with normal or symmetrical sensorineural hearing loss and normal cognitive function. Backward stepwise multivariate linear regression was performed to assess the association between plasma adiponectin concentrations and hearing level Z-scores. Further, backward stepwise logistic regression analysis was performed to determine the risk of hearing impairment by plasma adiponectin concentration.

RESULTS

Adiponectin concentrations were lower, and waist circumference (WC) was higher in subjects with Z-high in the upper 50% of Z-high. Z-high (correlation coefficient: β = -0·02; standard error [SE] = 0·01; P = 0·003), but not Z-middle or Z-low, was significantly associated with plasma adiponectin concentrations after adjusting for WC, systemic diseases, smoking and alcohol consumption. The risk of hearing impairment for high frequencies, but not low or middle frequencies, decreased by 0·97-fold (odds ratio ± SE = 0·97 ± 0·02, P = 0·048, 95% confidence interval = 0·93-1·00) for every 1-unit increase in adiponectin concentration, after adjusting for age, gender, WC, systemic diseases, smoking and alcohol consumption.

CONCLUSION

Plasma adiponectin may protect peripheral hearing function, particularly that related to high frequencies. Adiponectin may be a mediator of obesity-associated, age-related hearing impairment.

Protective role of hydrogen sulfide against noise-induced cochlear damage: a chronic intracochlear infusion model

Background

A reduction in cochlear blood flow plays an essential role in noise-induced hearing loss (NIHL). The timely regulation of cochlear perfusion determines the progression and prognosis of NIHL. Hydrogen sulfide (H₂S) has attracted increasing interest as a vasodilator in cardiovascular systems. This study identified the role of H₂S in cochlear blood flow regulation and noise protection.

Methodology/Principal Findings

The gene and protein expression of the H₂S synthetase cystathionine-γ-lyase (CSE) in the rat cochlea was examined using immunofluorescence and real-time PCR. Cochlear CSE mRNA levels varied according to the duration of noise exposure. A chronic intracochlear infusion model was built and artificial perilymph (AP), NaHS or DL-propargylglycine (PPG) were locally administered. Local sodium hydrosulfide (NaHS) significantly increased cochlear perfusion post-noise exposure. Cochlear morphological damage and hearing loss were alleviated in the NaHS group as measured by conventional auditory brainstem response (ABR), cochlear scanning electron microscope (SEM) and outer hair cell (OHC) count. The highest percentage of OHC loss occurred in the PPG group.

Conclusions/Significance

Our results suggest that H₂S plays an important role in the regulation of cochlear blood flow and the protection against noise. Further studies may identify a new preventive and therapeutic perspective on NIHL and other blood supply-related inner ear diseases.

Hearing sensitivity in older adults: associations with cardiovascular risk factors in the health, aging and body composition study

OBJECTIVES

To examine the association between cardiovascular disease (CVD) and its risk factors and age-associated hearing loss in a cohort of older black and white adults.

DESIGN

Cross-sectional cohort study.

SETTING

The Health, Aging, and Body Composition (Health ABC) Study, a community-based cohort study of older adults from Pittsburgh, Pennsylvania, and Memphis, Tennessee.

PARTICIPANTS

Two thousand forty-nine well-functioning adults (mean age 77.5; 37% black).

MEASUREMENTS

Pure-tone audiometry measurement and history of clinical CVD were obtained at the fourth annual follow-up visit. Pure-tone averages in decibels reflecting low (250, 500, and 1,000 Hz), middle (500, 1,000, and 2,000 Hz), and high (2,000, 4,000, and 8,000 Hz) frequencies were calculated for each ear. CVD risk factors, aortic pulse-wave velocity (PWV), and ankle-arm index (AAI) were obtained at study baseline.

RESULTS

In sex-stratified models, after adjustment for age, race, study site, and occupational noise exposure, risk factors associated with poorer hearing sensitivity in men included high triglyceride levels, high resting heart rate, and history of smoking. In women, poor hearing sensitivity was associated with high body mass index, high resting heart rate, fast PWV, and low AAI.

CONCLUSION

Modifiable risk factors for CVD may play a role in the development of age-related hearing loss.

The grainyhead-like 2 gene (GRHL2) single nucleotide polymorphism is not associated with age-related hearing impairment in Han Chinese

OBJECTIVES/HYPOTHESIS

The grainyhead-like 2 gene (GRHL2) was found to be associated with age-related hearing impairment (ARHI) in Europeans. We tested whether the same association exists in the Han Chinese population.

STUDY DESIGN

Individual cohort study.

METHODS

Among a total of 1,175 Han Chinese volunteers, 310 were classified into the case group (the 26% with poorest hearing), and 308 were placed into the control group (the 26% with best hearing) according to the Zhigh scores converted from the original frequency-specific hearing thresholds. The GRHL2 single nucleotide polymorphism locus (rs10955255: A/G) in intron 1 (coordinate: 102605581) shown in the HapMap was genotyped with correlation to the audiologic phenotypes.

RESULTS

The genotype distributions of GRHL2 (AA/AG/GG) were not significantly different between the control and the case groups (P = .349). Compared to genotype AA, the odds ratios of the GRHL2 genotypes AG and GG for ARHI were not significantly different after adjustment for other environmental risk factors by logistic regression analyses; 0.78 ± 0.139, 95% confidence interval (CI) = 0.55-1.10, P = .160 for AG; 0.85 ± 0.283, 95% CI = 0.44-1.63, P = .625 for GG. In each audiogram pattern, AA was most common, but the adjusted odds ratios of the genotypes AG and GG for ARHI still were not significantly different.

CONCLUSIONS

Our results showed no positive association between GRHL2 polymorphisms and ARHI in Han Chinese individuals. Population differences might be a key factor leading to nonreplication of the association.

Environmental and genetic factors in age-related hearing impairment

Age-related hearing impairment (ARHI), or presbycusis, is a complex disease with multifactorial etiology. It is the most prevalent sensory impairment in the elderly, and may have detrimental effects on their quality of life and psychological well-being. The aim of this paper is to give an overview of the current data on ARHI, focusing mainly on environmental agents and genetic predisposition in animal models and in humans. With improvement of our understanding of ARHI, treatment other than with amplification will be hopefully possible in the long term.

Effects of light smoking on extra-high-frequency auditory thresholds in young adults

There have been few reports showing a correlation between hearing levels and life style in young people. In this study, we succeeded in sensitively evaluating hearing levels in 51 young male adults of 21-23 years in age by 12 k Hz extra-high-frequency auditory thresholds, which cannot be measured by usual audiometry devices for clinical use. Noise exposure, alcohol consumption and sleeping time did not affect hearing levels in young adults. Auditory thresholds of 12 kHz frequency in smokers were significantly (p < 0.05) higher than those in non-smokers, while there were no differences in 1 kHz, 4 kHz and 8 kHz frequencies of hearing levels between smokers and non-smokers. Since the Brinkman Index (BI; cigarettes/day multiplied by number of years) of smokers in this study was from 12 to 60, our results suggest that even light smoking of less than 20 cigarettes/day for 3 years can result in the development of hearing loss of 12 kHz frequency in young adults. Binary logistic regression analysis again showed a correlation between hearing loss (≥ 40 dB of auditory thresholds in 12 kHz frequency) and light smoking (12 ≤ BI ≤ 60). Thus, this study showed that auditory threshold at 12 kHz frequency could be a sensitive marker for hearing in young adults. More importantly, we for the first time provided epidemiological evidence that light smoking might affect hearing level at 12 kHz frequency and revealed a new risk of light smoking.

A prospective study of cardiovascular risk factors and incident hearing loss in men

OBJECTIVES/HYPOTHESIS

Hearing loss is the most common sensory disorder in the United States, affecting more than 36 million people. Cardiovascular risk factors have been associated with the risk of hearing loss in cross-sectional studies, but prospective data are currently lacking.

STUDY DESIGN

Prospective cohort study.

METHODS

We prospectively evaluated the association between diagnosis of hypertension, diabetes mellitus, hypercholesterolemia, smoking, or body mass index (BMI) and incident hearing loss. Participants were 26,917 men in the Health Professionals Follow-up Study, aged 40 to 74 years at baseline in 1986. Study participants completed questionnaires about lifestyle and medical history every 2 years. Information on self-reported professionally diagnosed hearing loss and year of diagnosis was obtained from the 2004 questionnaire, and cases were defined as hearing loss diagnosed between 1986 and 2004. Multivariable-adjusted hazard ratios (HRs) were calculated using Cox proportional hazards regression models.

RESULTS

A total of 3,488 cases of hearing loss were identified. History of hypertension (HR 0.96; 95% confidence interval [CI], 0.88-1.03), diabetes mellitus (HR 0.92; 95% CI, 0.78-1.08), or obesity (HR 1.02; 95% CI, 0.90-1.15 for BMI >or=30 compared to normal range of 19-24.9) was not significantly associated with hearing-loss risk. Hypercholesterolemia (HR 1.10; 95% CI, 1.02-1.18) and past smoking history (HR 1.09; 95% CI, 1.01-1.17) were associated with a significantly increased risk of hearing loss after multivariate adjustment.

CONCLUSIONS

A history of hypertension, diabetes mellitus, or obesity is not associated with increased risk of hearing loss; a history of past smoking or hypercholesterolemia has a small but statistically significant association with increased risk of hearing loss in adult males.

The effects of smoking and alcohol consumption on age-related hearing loss: the Blue Mountains Hearing Study

OBJECTIVES

We aimed to investigate the temporal association between smoking or alcohol consumption and hearing loss, and to confirm previously published cross-sectional associations.

DESIGN

The Blue Mountains Hearing Study is a population-based survey of age-related hearing loss conducted in a defined suburban area, west of Sydney. Hearing loss was measured in 2956 participants (aged 50+ yrs) and was defined as the pure-tone average of frequencies 0.5, 1.0, 2.0, and 4.0 kHz >25 dB HL in the better ear (bilateral hearing loss). Alcohol consumption and smoking status were measured using an interviewer-administered questionnaire. Logistic regression was used to obtain odds ratios (OR) with 95% confidence intervals (95% CI) that compared the chances of having hearing loss in participants who did or did not smoke or consume alcohol, after adjusting for other factors previously reported to be associated with hearing loss.

RESULTS

The prevalence of hearing loss at baseline was 33.0% (N = 929) and the 5-year incidence of hearing loss was 17.9% (N = 156). Cross-sectional analysis demonstrated a significant protective association between the moderate consumption of alcohol (>1 but < or =2 drinks/day) and hearing function in older adults (compared with nondrinkers), OR 0.75 (95% CI, 0.57 to 0.98). Current smokers not exposed to occupational noise had a significantly higher likelihood of hearing loss after adjusting for multiple variables, OR 1.63 (95% CI, 1.01 to 2.64). A formal likelihood ratio test demonstrated that the interaction between smoking and noise exposure was not significant (p = 0.23). When the joint effects of alcohol consumption and smoking on hearing were explored, there was a trend for alcohol to have a protective relationship with hearing loss in smokers, but this was not statistically significant. However, the 5-year incidence of hearing loss was not predicted by either smoking or alcohol consumption.

CONCLUSIONS

This study confirms previously reported associations between alcohol consumption or smoking and prevalent hearing loss, but these were not demonstrated in temporal data. Other risk factors could confer greater vulnerability or cause the initial damage to hearing. Future large population-based studies, exploring the influence of other risk factors on the development of age-related hearing loss are warranted.

Heritability of audiometric shape parameters and familial aggregation of presbycusis in an elderly Flemish population

This study describes the heritability of audiometric shape parameters and the familial aggregation of different types of presbycusis in a healthy, otologically screened population between 50 and 75 years old. About 342 siblings of 64 families (average family-size: 5.3) were recruited through population registries. Audiometric shape was mathematically quantified by objective parameters developed to measure size, slope, concavity, percentage of frequency-dependent and frequency-independent hearing loss and Bulge Depth. The heritability of each parameter was calculated using a variance components model. Logistic regression models were used to estimate the odds ratios (ORs). Estimates of sibling recurrence risk ratios (lambda(s)) are also provided. Heritability estimates were generally higher compared to previous studies. ORs and lambda(s) for the parameters Total Hearing Loss (size), Uniform Hearing Loss (percentage of frequency-dependent hearing loss) and Bulge Depth suggest a higher heredity for severe types of presbycusis compared to moderate or mild types. Our results suggest that the separation of the parameter 'Total Hearing Loss' into the two parameters 'Uniform Hearing Loss' and 'Non-uniform Hearing Loss' could lead to the discovery of different genetic subtypes of presbycusis. The parameter 'Bulge Depth', instead of 'Concavity', seemed to be an important parameter for classifying subjects into 'susceptible' or 'resistant' to societal or intensive environmental exposure.

The Ala54Thr polymorphism in the fatty acid-binding protein 2 (FABP2) gene is associated with hearing impairment: a preliminary report

OBJECTIVE

The fatty acid-binding protein 2 (FABP2) is involved in the transport and metabolism of fatty acids. The FABP2 gene has been proposed as a candidate gene for diabetes and obesity. This study evaluates the hearing impairment risk in the Ala54Thr polymorphism of FABP2 in middle-aged and elderly Japanese.

METHODS

Our sample population comprised 1428 community-dwelling Japanese aged 40-86 years (mean+/-standard deviation [SD]: 63.1+/-9.8) who participated in the Study of Aging between 2004 and 2006. An average hearing threshold level greater than 25 dB in the better ear for frequencies 500, 1000, 2000 and 4000 Hz was defined as hearing impairment. Data were analyzed by means of a multiple logistic regression with adjustment for potential confounders.

RESULTS

The per-allele odds ratio for hearing impairment risk was 1.262 (95% confidence interval [CI]: 1.012-1.574) in model 1, adjusting for age, sex, history of ear disease, and history of occupational noise exposure; and 1.259 (CI: 1.009-1.571) in model 2, which adjusted for diabetes, body mass index and the histories of heart disease and hypertension, as well as the moderators in model 1. A significant adverse effect of the Thr54 variant on hearing was observed and the effect was independent of both diabetes and obesity in the present analyses.

CONCLUSIONS

This study demonstrated that the Ala54Thr polymorphism of FABP2 was associated with a risk of hearing impairment in middle-aged and elderly people. The results might support caloric restriction theory indirectly, but additional researches are desired.

Genome-wide SNP analysis reveals no gain in power for association studies of common variants in the Finnish Saami

The Saami from Fennoscandia are believed to represent an ancient, genetically isolated population with no evidence of population expansion. Theoretical work has indicated that under this demographic scenario, extensive linkage disequilibrium (LD) is generated by genetic drift. Therefore, it has been suggested that the Saami would be particularly suited for genetic association studies, offering a substantial power advantage and allowing more economic study designs. However, no study has yet assessed this claim. As part of a GWAS for a complex trait, we evaluated the relative power for association studies of common variants in the Finnish Saami. LD patterns in the Saami were very similar to those in the non-African HapMap reference panels. Haplotype diversity was reduced and, on average, levels of LD were higher in the Saami as compared with those in the HapMap panels. However, using a 'hidden' SNP approach we show that this does not translate into a power gain in association studies. Contrary to earlier claims, we show that for a given set of common SNPs, genomic coverage attained in the Saami is similar to that in the non-African HapMap panels. Nevertheless, the reduced haplotype diversity could potentially facilitate gene identification, especially if multiple rare variants play a role in disease etiology. Our results further indicate that the HapMap is a useful resource for genetic studies in the Saami.

Gender-specific associations of vision and hearing impairments with adverse health outcomes in older Japanese: a population-based cohort study

Background

Several epidemiological studies have shown that self-reported vision and hearing impairments are associated with adverse health outcomes (AHOs) in older populations; however, few studies have used objective sensory measurements or investigated the role of gender in this association. Therefore, we examined the association of vision and hearing impairments (as measured by objective methods) with AHOs (dependence in activities of daily living or death), and whether this association differed by gender.

Methods

From 2005 to 2006, a total of 801 residents (337 men and 464 women) aged 65 years or older of Kurabuchi Town, Gunma, Japan, participated in a baseline examination that included vision and hearing assessments; they were followed up through September 2008. Vision impairment was defined as a corrected visual acuity of worse than 0.5 (logMAR = 0.3) in the better eye, and hearing impairment was defined as a failure to hear a 30 dB hearing level signal at 1 kHz in the better ear. Information on outcomes was obtained from the town hall and through face-to-face home visit interviews. We calculated the risk ratios (RRs) of AHOs for vision and hearing impairments according to gender.

Results

During a mean follow-up period of 3 years, 34 men (10.1%) and 52 women (11.3%) had AHOs. In both genders, vision impairment was related to an elevated risk of AHOs (multi-adjusted RR for men and women together = 1.60, 95% CI = 1.05-2.44), with no statistically significant interaction between the genders. In contrast, a significant association between hearing impairment and AHOs (multi-adjusted RR = 3.10, 95% CI = 1.43-6.72) was found only in the men.

Conclusion

In this older Japanese population, sensory impairments were clearly associated with AHOs, and the association appeared to vary according to gender. Gender-specific associations between sensory impairments and AHOs warrant further investigation.

Analysis of auditory measures in normal hearing young male adult cigarette smokers using multiple variable selection methods with predictive validation assessments

Studies have shown that cigarette smoking is a risk factor for hearing loss; however, no information is available on auditory preclinical indicators in young chronic cigarette smokers. Cigarette smoking involves exposure to many harmful chemicals including carbon monoxide (CO). In this study, the CO level in 16 young normal hearing male chronic smokers was measured with a CO monitor, and was used as the outcome measure. Subjects were administered a battery of audiological tests that included behavioral and electrophysiologic measures. The goal was to investigate which auditory test measures can be used as potential predictors of the outcome measure. Using ordinary least squares estimation procedures with best-subsets selection and bootstrapped stepwise variable selection procedures, an optimal predictive multiple linear regression model was selected. Results of this approach indicated that auditory brainstem response peak V amplitudes and distortion product otoacoustic emissions had the highest predictive value and accounted for most of the variability.

Association of central obesity with the severity and audiometric configurations of age-related hearing impairment

To investigate the effect of central obesity on the severity and characteristics of age-related hearing impairment (ARHI), we recruited 690 adult subjects with normal or symmetrical sensorineural hearing loss (SNHL). The effects of age, gender, morphometry, habits, systemic diseases, and environmental noise exposure on average pure tone hearing level at low frequencies (pure tone audiometry (PTA)-low) and high frequencies (PTA-high) were analyzed. After adjusting for age, gender, systemic disease, and other variables, waist circumference (WC) showed a significant positive association with PTA-low and PTA-high. In females, PTA-low and PTA-high only showed significant positive association with age, but not with WC or other variables. However, PTA-high showed a positive association with borderline significance with WC in female subjects older than 55. In males, WC as well as age and noise exposure showed significant positive associations with both PTA-low and PTA-high, primarily in subjects younger than 55. When both WC and BMI were taken into account in a backward stepwise multivariate linear regression analysis, WC, but not BMI, showed a significant positive association with PTA-low and PTA-high in males younger than 55, and with PTA-high with borderline significance in females older than 55. However, the audiogram patterns were not significantly affected by central obesity in either age or gender. Our results suggest that WC was, even after adjustment for BMI, an independent risk factor of ARHI, particularly for low and high frequencies in males younger than 55 and for high frequencies in female subjects older than 55.

Genome-wide SNP-based linkage scan identifies a locus on 8q24 for an age-related hearing impairment trait

Age-related hearing impairment (ARHI), or presbycusis, is a very common multifactorial disorder. Despite the knowledge that genetics play an important role in the etiology of human ARHI as revealed by heritability studies, to date, its precise genetic determinants remain elusive. Here we report the results of a cross-sectional family-based genetic study employing audiometric data. By using principal component analysis, we were able to reduce the dimensionality of this multivariate phenotype while capturing most of the variation and retaining biologically important features of the audiograms. We conducted a genome-wide association as well as a linkage scan with high-density SNP microarrays. Because of the presence of genetic population substructure, association testing was stratified after which evidence was combined by meta-analysis. No association signals reaching genome-wide significance were detected. Linkage analysis identified a linkage peak on 8q24.13-q24.22 for a trait correlated to audiogram shape. The signal reached genome-wide significance, as assessed by simulations. This finding represents the first locus for an ARHI trait.