Association of Audiometric Measures with plasma long chain polyunsaturated fatty acids in a high-fish eating population: The Seychelles Child Development Study

Omega-3 fatty acids and health of auditory and vestibular systems: a comprehensive review

PURPOSE

The purpose of this study was to comprehensively review animal and human studies that explore the role of omega-3 PUFAs in maintaining the health of the auditory organ across all life stages.

METHODS

This narrative review involved searching Scopus, PubMed, Google Scholar, and Cochrane Library databases for relevant articles from December 1980 to July 2023.

RESULTS

some animal and human studies suggest that both deficiency and excessive intake of long-chain omega-3 PUFAs, particularly docosahexaenoic acid (DHA), can lead to auditory neural conduction impairment and reduced hearing acuity from fetal development to old age (presbycusis). These effects are likely to be dependent on the dosage. Some research indicates that an excessive intake of omega-3, rather than a deficiency, can result in nutritional toxicity and hearing impairments. Animal studies highlight the positive impact of omega-3 supplements with high DHA content in addressing hearing damage, but human research on this subject is limited. Furthermore, certain studies propose that omega-3 PUFAs may prevent or delay age-related hearing loss, with high plasma omega-3 concentration, particularly long-chain omega-3 PUFA, linked to reduced hearing loss. Additionally, consuming fish more than twice a week may be associated with a lower risk of hearing loss in adulthood, with these effects potentially influenced by age and gender. However, the majority of studies have been conducted on animals, and clinical trials are scarce. Research on the influence of omega-3 PUFAs on the peripheral and central vestibular systems remains limited.

CONCLUSION

This article delves into the impact of omega-3 on the auditory-vestibular system, exploring its influence on neurodevelopment, protection, and treatment. It not only highlights specific research gaps but also offers valuable insights for potential future studies.

Fatty acid binding protein type 7 deficiency preserves auditory function in noise-exposed mice

Fatty acid-binding protein 7 (FABP7) is vital for uptake and trafficking of fatty acids in the nervous system. To investigate the involvement of FABP7 in noise-induced hearing loss (NIHL) pathogenesis, we used Fabp7 knockout (KO) mice generated via CRISPR/Cas9 in the C57BL/6 background. Initial auditory brainstem response (ABR) measurements were conducted at 9 weeks, followed by noise exposure at 10 weeks. Subsequent ABRs were performed 24 h later, with final measurements at 12 weeks. Inner ears were harvested 24 h after noise exposure for RNA sequencing and metabolic analyses. We found no significant differences in initial ABR measurements, but Fabp7 KO mice showed significantly lower thresholds in the final ABR measurements. Hair cell survival was also enhanced in Fabp7 KO mice. RNA sequencing revealed that genes associated with the electron transport chain were upregulated or less impaired in Fabp7 KO mice. Metabolomic analysis revealed various alterations, including decreased glutamate and aspartate in Fabp7 KO mice. In conclusion, FABP7 deficiency mitigates cochlear damage following noise exposure. This protective effect was supported by the changes in gene expression of the electron transport chain, and in several metabolites, including excitotoxic neurotransmitters. Our study highlights the potential therapeutic significance of targeting FABP7 in NIHL.

Association between nineteen dietary fatty acids and hearing thresholds: findings from a nationwide survey

INTRODUCTION

Hearing loss is a prevalent health concern, and dietary factors, such as fatty acid intake, may play a role in its development. The current study aimed to investigate the association between the intake of dietary fatty acids and hearing thresholds among U.S. adults.

METHODS

The researchers examined data from the National Health and Nutrition Examination Survey (NHANES), including 7,623 participants with available dietary fatty acid intake and audiometry data. Dietary fatty acid intake was assessed using dietary recalls, and hearing thresholds were measured using pure-tone audiometry. Multivariate linear regression models and smoothing curve fitting were utilized to explore the associations between dietary fatty acid intake and hearing thresholds, adjusting for relevant covariates.

RESULTS

This study reveals a direct association between both low and high frequency pure tone average (PTA) hearing thresholds and the dietary intake of total saturated fatty acids (SFAs) and total polyunsaturated fatty acids (PUFAs). Conversely, the intake of total monounsaturated fatty acids (MUFAs) demonstrates an inverted U-shaped correlation with low-frequency and high-frequency PTA hearing thresholds, having inflection points at 11.91 (energy (%)) and 10.88 (energy (%)), respectively.

CONCLUSION

Dietary intake of certain fatty acids may influence hearing thresholds in adults.

The association of auditory function measures with low-level methylmercury from oceanic fish consumption and mercury vapor from amalgam: The Seychelles Child Development Study Nutrition 1 Cohort

BACKGROUND

Some authors have reported that low-level exposure to methylmercury (MeHg) adversely impacts measures of auditory function. These reports, however, are not consistent in their findings. Consequently, we examined auditory function in a population exposed to low-level methylmercury (MeHg) exposure from fish consumption and to mercury vapor (Hg0) from dental amalgams. We analyzed their associations with the participants hearing acuity, absolute and interwave ABR latencies, and otoacoustic emissions (distortion product/DPOAE and click evoked/CEOAE).

DESIGN

We administered an audiometry test battery to 246 participants from the Seychelles Child Development Study (SCDS) Nutrition Cohort 1 (NC1) at 9 years of age. The test battery included standard pure-tone audiometry, tympanometry, Auditory Brainstem Responses (ABR) and Distortion Product and Click Evoked Otoacoustic Emissions (DPOAE and CEOAE) testing. We measured prenatal MeHg exposure in maternal hair and postnatal MeHg in children's hair. We approximated prenatal Hg0 exposure using maternal amalgam surface area and postnatal Hg0 using children amalgam surface area. Complete exposure records and audiometric data were available on 210 participants and in them we analyzed the association of MeHg and Hg0 exposures with auditory outcomes using covariate-adjusted linear regression models adjusted for sex and tympanometric pressure.

RESULTS

Hg exposures were similar for both sexes. Seven of the 210 evaluable participants examined had either a mild (5) or moderate (2) hearing loss. Four had a mild monaural hearing loss and 3 had either a mild (1) or moderate (2) bilateral hearing loss. No participant had greater than a moderate hearing loss in either ear. Hg exposures were higher in participants with either a mild or moderate hearing loss, but these differences were not statistically significant. Among the 210 with complete data, neither prenatal nor postnatal MeHg nor Hg0 exposure was statistically significantly associated with any of the ABR endpoints (p > 0.05 for all 72 associations). Neither prenatal nor postnatal Hg0 exposure was associated with any of the OAE endpoints (p > 0.05). MeHg exposure was statistically associated with 6 of the 56 DPOAE endpoints (p-values between 0.0001 and 0.023), but none of the 40 CEOAE endpoints. Two of the associations occurred with prenatal MeHg exposures and 1 of those would suggest a beneficial effect. Four of the other associations occurred with postnatal MeHg exposures with only 2 found in left ears of both males and females and the other 2 in the left and right ear of females at only one frequency.

CONCLUSION

Overall, these data do not present a clear and consistent pattern to suggest that the auditory system is negatively affected by low-level methylmercury exposure due to dietary consumption of oceanic fish or mercury vapor exposure from dental amalgams.

Serum polyunsaturated fatty acids and hearing threshold shifts in adults in the United States: A cross-sectional study

Background

Few studies have evaluated the association between polyunsaturated fatty acids (PUFAs) and hearing levels. This study aimed to investigate the association between serum PUFAs and hearing threshold shifts in US adults.

Methods

We investigated 913 adults from the National Health and Nutrition Examination Survey (NHANES) 2011-2012. Multivariate linear regression analyses were conducted to evaluate associations between PUFA and hearing threshold shifts.

Results

Overall, 11 serum PUFAs were inversely associated with low-frequency thresholds, especially in men, and were positively related to high-frequency thresholds, particularly in the 40-59 years old cohort. Furthermore, some serum PUFAs were positively associated with both hearing threshold subgroups in women.

Conclusion

Some PUFAs tend to be beneficial for low-frequency hearing status and detrimental to the high-frequency hearing threshold. The male sex may play a protective role in this association, while the female sex and middle age may be detrimental in the effect of PUFAs on hearing function.

Dietary fat intake and risk of disabling hearing impairment: a prospective population-based cohort study

Purpose

To examine the associations of specific dietary fats with the risk of disabling hearing impairment in the UK Biobank study.

Methods

This cohort study investigated 105,592 participants (47,308 men and 58,284 women) aged ≥ 40 years. Participants completed a minimum of one valid 24-h recall (Oxford Web-Q). Dietary intake of total fatty acids, polyunsaturated fatty acids (PUFA), saturated fatty acids (SFA), and monounsaturated fatty acids (MUFA) was assessed at baseline. Functional auditory capacity was measured with a digit triplet test (DTT), and disabling hearing impairment was defined as a speech reception threshold in noise > − 3.5 dB in any physical exam performed during the follow-up.

Results

Over a median follow-up of 3.2 (SD: 2.1) years, 832 men and 872 women developed disabling hearing impairment. After adjustment for potential confounders, including lifestyles, exposure to high-intensity sounds, ototoxic medication and comorbidity, the hazard ratios (HRs), and 95% confidence interval (CI) of disabling hearing function, comparing extreme quintiles of intakes were 0.91 (0.71–1.17) for total fat, 1.09 (0.83–1.44) for PUFA, 0.85 (0.64–1.13) for SFA and 1.01 (0.74–1.36) for MUFA among men. Among women, HRs comparing extreme intakes were 0.98 (0.78–1.24) for total fat, 0.69 (0.53–0.91) for PUFA, 1.26 (0.96–1.65) for SFA, and 0.91 (0.68–1.23) for MUFA. Replacing 5% of energy intake from SFA with an equivalent energy from PUFA was associated with 25% risk reduction (HR: 0.75; 95% CI: 0.74–0.77) among women.

Conclusions

PUFA intake was associated with decreased risk of disabling hearing function in women, but not in men.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02644-7.