A prospective case-controlled study of 197 men, 50-60 years old, selected at random from a population at risk from hyperlipidaemia to examine the relationship between hyperlipidaemia and sensorineural hearing loss

Hearing in Adults: A Digital Reprint of the Main Report From the MRC National Study of Hearing

The 1011-page book, Hearing in Adults, published in 1995, contains the fullest report of the United Kingdom’s Medical Research Council National Study of Hearing. It was designed to determine the prevalence and distribution in Great Britain of audiometrically measured hearing loss as a function of age, gender, occupation, and noise exposure. The study’s size, quality, and breadth made it unique when it was done in the 1980s. These qualities remain, and its data are still the primary U.K. source for the prevalence of auditory problems. However, only 550 copies were printed, and the book is essentially unobtainable today. We describe here a fully searchable, open-access, digital (PDF) “reprinting” of Hearing in Adults, summarizing the study’s design and the book’s contents, together with a brief commentary in the light of subsequent developments.

Low-fat and low-protein diets are associated with hearing discomfort among the elderly of Korea

Research on the effect of low-fat intake on hearing is limited. This study aimed to elucidate the relationship between fat, carbohydrate and protein intake and the presence of hearing discomfort among the elderly. The Korean National Health and Nutrition Examination Survey was conducted from 2009 through to 2012. A total of 4615 participants ranging in age from 60 to 80 years underwent a pure-tone audiometric evaluation, a physical examination and a nutritional survey. The associations between the participants' hearing thresholds and their protein/fat/carbohydrate intake/total energy intake were analysed using simple and multiple regression models with complex sampling adjusted for confounding factors, such as BMI, income level, smoking status and a history of hypertension, hyperlipidaemia and diabetes. Low fat and protein intakes were associated with hearing discomfort (OR 0·82, 95 % CI 0·71, 0·96, P=0·011; OR 0·81, 95 % CI 0·67, 0·96, P=0·017, respectively). This study revealed that low fat and protein intakes are associated with hearing discomfort in the elderly Korean population.

Dietary intake of cholesterol is positively associated and use of cholesterol-lowering medication is negatively associated with prevalent age-related hearing loss

We aimed to assess associations between dietary intake of fats (saturated and monounsaturated fats and cholesterol) and certain food groups (butter, margarine, and nuts) with the prevalence, incidence, and progression of age-related hearing loss. We also aimed to investigate the link between serum lipids and cholesterol-lowering medication (statins) and hearing loss. The Blue Mountains Hearing Study is a population-based survey of age-related hearing loss. Hearing loss was measured in 2956 participants (aged ≥50 y) and was defined as the pure-tone average (PTA) of frequencies 0.5, 1.0, 2.0, and 4.0 kHz > 25 dB hearing level (PTA(0.5-4 kHz)). Dietary data were collected using a semiquantitative FFQ. After multivariable adjustment, the likelihood of prevalent hearing loss increased from the lowest (reference) to the highest quartile of dietary cholesterol intake (P-trend = 0.04). Among persons self-reporting statin use (n = 274), a 48% reduced odds of prevalent hearing loss was observed after multivariable adjustment [OR = 0.52 (95% CI = 0.29-0.93)]. Participants in the second and 3rd quartiles of dietary monounsaturated fat intake compared with those in the first quartile (reference) had a significantly reduced risk of hearing loss progression 5 y later [multivariable-adjusted OR = 0.39 (95% CI = 0.21-0.71)] and [OR = 0.51 (95% CI = 0.29-0.91)], respectively. Our results suggest that a diet high in cholesterol could have adverse influences on hearing, whereas treatment with statins and consumption of monounsaturated fats may have a beneficial influence.

The role of dyslipidemia in sensorineural hearing loss in children

OBJECTIVE

The relationship between dyslipidemia and hearing is controversial; especially in children, the available evidences are scarce. This study is designed to determine whether dyslipidemia is associated with sensorineural hearing loss in a group of 5-18-year-old children and adolescents.

METHODS

Through an analytic cross-sectional study, records of all 5-18-year-old children who attended the pediatric endocrinology clinic of Loghman Hospital in Tehran, Iran, between April 2007 and April 2009 were reviewed. Records with a lipid profile were determined. Lipid profiles were repeated for eligible cases; they were enrolled if the results were the same as before (normal or dyslipidemic). Hearing loss, speech discrimination scores and lipid profiles were analyzed.

RESULTS

When controlled for age and sex, no association between dyslipidemia and sensorineural hearing loss were found. There was also no statistically significant relationship between dyslipidemia and sensorineural hearing loss in different age groups.

CONCLUSIONS

Dyslipidemia seems to have no association with sensorineural hearing loss in 5-18 years old children according to this study.

Hyperlipidemia in noise-induced hearing loss

OBJECTIVES

To assess the influence of hyperlipidemia on the development of noise-induced hearing loss (NIHL).

STUDY DESIGN

This case-control study analyzed data from the Department of Preventive Medicine at one academic medical center in southern Taiwan.

SUBJECTS AND METHODS

We collected the laboratory data from routine health examinations administered to workers who were exposed to noise greater than 85 dBA over a one-year period. We analyzed the relationships of cholesterol and triglyceride levels with NIHL.

RESULTS

A total of 4071 cases were analyzed. After adjusting for age and gender, hypertriglyceridemia was found to be related to NIHL (aOR = 1.281; 95% CI, 1.088-1.507), but hypercholesterolemia was not (aOR = 0.951; 95% CI, 0.795-1.138).

CONCLUSIONS

This study, one of the largest to date to study the relationship between hyperlipidemia and NIHL, found that individuals with hypertriglyceridemia are at greater risk of NIHL. On the basis of this finding, workers exposed to high noise levels should be educated on control of triglyceride levels to help reduce their risk of NIHL.

Morphological and functional alterations of the cochlea in apolipoprotein E gene deficient mice

The relationship between hyperlipidemia and sensorineural hearing loss remains obscure. In this study, we elucidate for the first time the cochlear morphological and auditory alterations and their relationships with hyperlipidemia, atherosclerosis, and endothelial dysfunction in apolipoprotein-E knockout (ApoE-KO) mice. Ten-week-old ApoE-KO mice were fed either atherosclerotic diet (1.25% cholesterol) or normal diet. Wild type mice (C57BL/6J) served as normal controls. Fourteen weeks later, marked hyperlipidemia, atherosclerosis, endothelial dysfunction, and hearing impairment, especially in the high frequencies, had developed in ApoE-KO mice as compared with C57BL/6J mice (P<0.001). A high positive correlation between hearing loss and the extent of atherosclerosis and plasma total cholesterol levels was found. Hearing loss, especially at high frequencies, was detected in all ApoE-KO mice. Hair cell loss mainly at the base turn, thickening of vascular intima, and lumen stenosis of the spiral modiolar artery (SMA) in cochlea were also found; these histological changes were exacerbated by the atherosclerotic diet. Furthermore, endothelial nitric oxide synthase (eNOS) in aortic wall and cochlea was distinctly reduced in ApoE-KO mice. These results demonstrate that hyperlipidemia and atherosclerosis can induce alterations in cochlear morphology and function. The stenosis of SMA, which may cause cochlear ischemia and hypoxia, endothelial dysfunction, and low eNOS activity, may contribute to hearing loss.