Integrating gender analysis into research: reflections from the Gender-Net Plus workshop.

Gender equality has been a crosscutting issue in Horizon 2020 with three objectives: gender balance in decision-making, gender balance and equal opportunities in project teams at all levels, and inclusion of the gender dimension in research and innovation content. Between 2017 and 2022, the EU funded, in collaboration with national agencies, 13 transnational projects under "GENDER-NET Plus" that explored how to best integrate both sex and gender into studies ranging from social sciences, humanities, and health research. As the projects neared completion, forty researchers from these interdisciplinary teams met in November 2022 to share experiences, discuss challenges, and consider the best ways forward to incorporate sex and gender in research. Here, we summarize the reflections from this workshop and provide some recommendations for i) how to plan the studies (e.g., how to define sex and/or gender and their dimensions, rationale for the hypotheses, identification of data that can best answer the research question), ii) how to conduct them (e.g., adjust definitions and dimensions, perform pilot studies to ensure proper use of terminology and revise until consensus is achieved), and iii) how to analyze and report the findings being mindful of any real-world impact.

Pharmacological Approaches to Hearing Loss.

Hearing disorders pose significant challenges to individuals suffering them and their overall quality of life, emphasizing the critical need for advanced pharmacological approaches to address these conditions. Current treatment options often focus on amplification devices, cochlear implants, or other rehabilitative therapies, leaving a substantial gap in effective pharmacological interventions. Advancements in our understanding of the molecular and cellular mechanisms involved in hearing disorders induced by noise, aging and ototoxicity have opened new avenues for drug development, some of which have led to a number of clinical trials with promising results. Development of optimal drug delivery solutions in animals and humans can also help enhance the targeted delivery of medications to the ear. Moreover, large genome studies contributing to genetic understanding of hearing loss in humans combined with advanced molecular technologies in animal studies have shown a great potential to increase our understanding of the etiologies of hearing loss. The auditory system exhibits circadian rhythms and temporal variations in its physiology, its vulnerability to auditory insults, and its responsiveness to drug treatments. The cochlear clock rhythms are under the control of the glucocorticoid system and has led to pre-clinical evidence suggesting that the risk/benefit profile of hearing disorder treatments using chronopharmacological approaches. If translatable to the bedside, such approaches may improve the outcome of clinical trials. Ongoing research into the molecular and genetic basis of auditory disorders, coupled with advancements in drug formulation and delivery, as well as optimized timing of drug administration, holds great promise of more effective treatments. Significance Statement Hearing disorders pose significant challenges to individuals and their overall quality of life, emphasizing the critical need for advanced pharmacological approaches to address these conditions. Ongoing research into the molecular and genetic basis of auditory disorders, coupled with advancements in drug delivery procedures, and optimized timing of drug administration, holds the promise of more effective treatments.

The out-of-pocket expenses of people with tinnitus in Europe.

BACKGROUND: Despite the high frequency of tinnitus and its impact on wellbeing, little is known about its economic burden and no data to our knowledge are available on out-of-pocket (OOP) expenses. METHODS: In 2022 a survey was conducted on OOP costs of tinnitus. We enrolled 679 participants with slight, moderate and severe tinnitus in Italy, United Kingdom, Netherlands, Germany and Spain. We estimated annual OOP expenses for tinnitus-related healthcare visits, treatments, medications and alternative medicine practices. Prevalence of tinnitus in the general population, obtained from a representative survey we conducted in Europe in 2017-2018, was used to generalise costs for people with any tinnitus at the national level. RESULTS: OOP expenses were 368€ (95% confidence intervals (CI), 78€-690€), 728€ (95% CI, 316€-1,288€), and 1,492€ (95% CI, 760€-2,688€) for slight, moderate, and severe tinnitus, respectively, with annual expenditure of 565€ for people with any tinnitus: 209€ for healthcare visits, 93€ for treatments, 16€ for drugs, 64€ for hearing supporting systems and 183€ for acupuncture, homeopathy and osteopathy. Individuals with slight, moderate, and severe tinnitus expressed a willingness to invest 1.6, 4.3, and 7.0 times their monthly income, respectively, to achieve complete relief from tinnitus. CONCLUSIONS: This study offers for the first time insights into the OOP expenses incurred by individuals with tinnitus. OOP expenses exhibited substantial variations based on severity status, accounting for more than 17 thousand million€ in the countries considered. In terms of financial burden, these findings align tinnitus to the recognised leading disabilities, including back pain and migraine.

Unraveling the role of Slc10a4 in auditory processing and sensory motor gating: Implications for neuropsychiatric disorders?

BACKGROUND: Psychiatric disorders, such as schizophrenia, are complex and challenging to study, partly due to the lack of suitable animal models. However, the absence of the Slc10a4 gene, which codes for a monoaminergic and cholinergic associated vesicular transporter protein, in knockout mice (Slc10a4-/-), leads to the accumulation of extracellular dopamine. A major challenge for studying schizophrenia is the lack of suitable animal models that accurately represent the disorder. We sought to overcome this challenge by using Slc10a4-/- mice as a potential model, considering their altered dopamine levels. This makes them a potential animal model for schizophrenia, a disorder known to be associated with altered dopamine signaling in the brain. METHODS: The locomotion, auditory sensory filtering and prepulse inhibition (PPI) of Slc10a4-/- mice were quantified and compared to wildtype (WT) littermates. Intrahippocampal electrodes were used to record auditory event-related potentials (aERPs) for quantifying sensory filtering in response to paired-clicks. The channel above aERPs phase reversal was chosen for reliably comparing results between animals, and aERPs amplitude and latency of click responses were quantified. WT and Slc10a4-/- mice were also administered subanesthetic doses of ketamine to provoke psychomimetic behavior. RESULTS: Baseline locomotion during auditory stimulation was similar between Slc10a4-/- mice and WT littermates. In WT animals, normal auditory processing was observed after i.p saline injections, and it was maintained under the influence of 5 mg/kg ketamine, but disrupted by 20 mg/kg ketamine. On the other hand, Slc10a4-/- mice did not show significant differences between N40 S1 and S2 amplitude responses in saline or low dose ketamine treatment. Auditory gating was considered preserved since the second N40 peak was consistently suppressed, but with increased latency. The P80 component showed higher amplitude, with shorter S2 latency under saline and 5 mg/kg ketamine treatment in Slc10a4-/- mice, which was not observed in WT littermates. Prepulse inhibition was also decreased in Slc10a4-/- mice when the longer interstimulus interval of 100 ms was applied, compared to WT littermates. CONCLUSION: The Slc10a4-/- mice responses indicate that cholinergic and monoaminergic systems participate in the PPI magnitude, in the temporal coding (response latency) of the auditory sensory gating component N40, and in the amplitude of aERPs P80 component. These results suggest that Slc10a4-/- mice can be considered as potential models for neuropsychiatric conditions.

Screening for Circulating Inflammatory Proteins Does Not Reveal Plasma Biomarkers of Constant Tinnitus.

BACKGROUND AND OBJECTIVE: Tinnitus would benefit from an objective biomarker. The goal of this study is to identify plasma biomarkers of constant and chronic tinnitus among selected circulating inflammatory proteins. METHODS: A case-control retrospective study on 548 cases with constant tinnitus and 548 matched controls from the Swedish Tinnitus Outreach Project (STOP), whose plasma samples were examined using Olink's Inflammatory panel. Replication and meta-analysis were performed using the same method on samples from the TwinsUK cohort. Participants from LifeGene, whose blood was collected in Stockholm and Umeå, were recruited to STOP for a tinnitus subtyping study. An age and sex matching was performed at the individual level. TwinsUK participants (n = 928) were selected based on self-reported tinnitus status over 2 to 10 years. Primary outcomes include normalized levels for 96 circulating proteins, which were used as an index test. No reference standard was available in this study. RESULTS: After adjustment for age, sex, BMI, smoking, hearing loss, and laboratory site, the top proteins identified were FGF-21, MCP4, GDNF, CXCL9, and MCP-1; however, these were no longer statistically significant after correction for multiple testing. Stratification by sex did not yield any significant associations. Similarly, associations with hearing loss or other tinnitus-related comorbidities such as stress, anxiety, depression, hyperacusis, temporomandibular joint disorders, and headache did not yield any significant associations. Analysis in the TwinsUK failed in replicating the top candidates. Meta-analysis of STOP and TwinsUK did not reveal any significant association. Using elastic net regularization, models exhibited poor predictive capacity tinnitus based on inflammatory markers [sensitivity = 0.52 (95% CI 0.47-0.57), specificity = 0.53 (0.48-0.58), positive predictive value = 0.52 (0.47-0.56), negative predictive values = 0.53 (0.49-0.58), and AUC = 0.53 (0.49-0.56)]. DISCUSSION: Our results did not identify significant associations of the selected inflammatory proteins with constant tinnitus. Future studies examining longitudinal relations among those with more severe tinnitus and using more recent expanded proteomics platforms and sampling of cerebrospinal fluid could increase the likelihood of identifying relevant molecular biomarkers.

Alterations of auditory sensory gating in mice with noise-induced tinnitus treated with nicotine and cannabis extract.

Tinnitus is a phantom sound perception affecting both auditory and limbic structures. The mechanisms of tinnitus remain unclear and it is debatable whether tinnitus alters attention to sound and the ability to inhibit repetitive sounds, a phenomenon also known as auditory gating. Here we investigate if noise exposure interferes with auditory gating and whether natural extracts of cannabis or nicotine could improve auditory pre-attentional processing in noise-exposed mice. We used 22 male C57BL/6J mice divided into noise-exposed (exposed to a 9-11 kHz narrow band noise for 1 h) and sham (no sound during noise exposure) groups. Hearing thresholds were measured using auditory brainstem responses, and tinnitus-like behavior was assessed using Gap prepulse inhibition of acoustic startle. After noise exposure, mice were implanted with multi-electrodes in the dorsal hippocampus to assess auditory event-related potentials in response to paired clicks. The results showed that mice with tinnitus-like behavior displayed auditory gating of repetitive clicks, but with larger amplitudes and longer latencies of the N40 component of the aERP waveform. The combination of cannabis extract and nicotine improved the auditory gating ratio in noise-exposed mice without permanent hearing threshold shifts. Lastly, the longer latency of the N40 component appears due to an increased sensitivity to cannabis extract in noise-exposed mice compared to sham mice. The study suggests that the altered central plasticity in tinnitus is more sensitive to the combined actions on the cholinergic and the endocannabinoid systems. Overall, the findings contribute to a better understanding of pharmacological modulation of auditory sensory gating.

Advancing the 3Rs: innovation, implementation, ethics and society.

The 3Rs principle of replacing, reducing and refining the use of animals in science has been gaining widespread support in the international research community and appears in transnational legislation such as the European Directive 2010/63/EU, a number of national legislative frameworks like in Switzerland and the UK, and other rules and guidance in place in countries around the world. At the same time, progress in technical and biomedical research, along with the changing status of animals in many societies, challenges the view of the 3Rs principle as a sufficient and effective approach to the moral challenges set by animal use in research. Given this growing awareness of our moral responsibilities to animals, the aim of this paper is to address the question: Can the 3Rs, as a policy instrument for science and research, still guide the morally acceptable use of animals for scientific purposes, and if so, how? The fact that the increased availability of alternatives to animal models has not correlated inversely with a decrease in the number of animals used in research has led to public and political calls for more radical action. However, a focus on the simple measure of total animal numbers distracts from the need for a more nuanced understanding of how the 3Rs principle can have a genuine influence as a guiding instrument in research and testing. Hence, we focus on three core dimensions of the 3Rs in contemporary research: (1) What scientific innovations are needed to advance the goals of the 3Rs? (2) What can be done to facilitate the implementation of existing and new 3R methods? (3) Do the 3Rs still offer an adequate ethical framework given the increasing social awareness of animal needs and human moral responsibilities? By answering these questions, we will identify core perspectives in the debate over the advancement of the 3Rs.

Delivery of gene therapy through a cerebrospinal fluid conduit to rescue hearing in adult mice.

Inner ear gene therapy has recently effectively restored hearing in neonatal mice, but it is complicated in adulthood by the structural inaccessibility of the cochlea, which is embedded within the temporal bone. Alternative delivery routes may advance auditory research and also prove useful when translated to humans with progressive genetic-mediated hearing loss. Cerebrospinal fluid flow via the glymphatic system is emerging as a new approach for brain-wide drug delivery in rodents as well as humans. The cerebrospinal fluid and the fluid of the inner ear are connected via a bony channel called the cochlear aqueduct, but previous studies have not explored the possibility of delivering gene therapy via the cerebrospinal fluid to restore hearing in adult deaf mice. Here, we showed that the cochlear aqueduct in mice exhibits lymphatic-like characteristics. In vivo time-lapse magnetic resonance imaging, computed tomography, and optical fluorescence microscopy showed that large-particle tracers injected into the cerebrospinal fluid reached the inner ear by dispersive transport via the cochlear aqueduct in adult mice. A single intracisternal injection of adeno-associated virus carrying solute carrier family 17, member 8 (Slc17A8), which encodes vesicular glutamate transporter-3 (VGLUT3), rescued hearing in adult deaf Slc17A8-/- mice by restoring VGLUT3 protein expression in inner hair cells, with minimal ectopic expression in the brain and none in the liver. Our findings demonstrate that cerebrospinal fluid transport comprises an accessible route for gene delivery to the adult inner ear and may represent an important step toward using gene therapy to restore hearing in humans.

The Role of Diet in Tinnitus Onset: A Hospital-Based Case-Control Study from Italy.

Knowledge on the role of diet in tinnitus onset is mostly based on few cross-sectional studies. In 2016-2019 we conducted a hospital-based case-control study in northern Italy on 185 incident idiopathic tinnitus cases and 198 controls, providing data on dietary habits through a 37-item food-frequency questionnaire. Odds ratios (OR) for tinnitus risk were derived through unconditional multiple logistic regression models. Moderate-to-high vs. low intake of caffeine (OR, 0.49; 95% confidence interval (CI), 0.24-0.99) and butter (OR, 0.46; 95% CI, 0.23-0.93), and high vs. low intake of poultry (OR, 0.43; 95% CI, 0.23-0.81), prosciutto (OR, 0.44; 95% CI, 0.23-0.85), and legumes (OR, 0.50; 95% CI, 0.28-0.92) were inversely associated with tinnitus onset. Other food items, including cereals, red meat, fish, vegetables, and fruit did not show any statistically significant relationship. The variety of food consumed decreased the risk of tinnitus (OR for at least 20 vs. less than 16 different food items, 0.47; 95% CI, 0.24-0.90). Our findings highlight the importance of diet in tinnitus onset and confirm a potential inverse association of protein-rich food and caffeine on the incidence of tinnitus. Confirmation of our findings in longitudinal studies is necessary before proving any diet recommendations for tinnitus prevention.

Low Evidence for Tinnitus Risk Factors: A Systematic Review and Meta-analysis.

AIMS/HYPOTHESIS: Identifying risk factors for tinnitus could facilitate not only the recommendations for prevention measures, but also identifying potential pathways for new interventions. This study reports the first comprehensive systematic review of analytical observational studies able to provide information about causality (i.e., case-control and cohort designs). METHODS: A literature search of four electronic databases identified epidemiological studies published on tinnitus and different exposures. Independent raters screened all studies, extracted data, and evaluated study quality using the Newcastle-Ottawa Scale. Reported relative risks (RR), hazard ratios (HR), odds ratios (OR), and prevalence ratios (PR) with 95% confidence intervals (CI) were used to compute crude estimates of RR for tinnitus risk factors. RESULTS: From 2389 records identified, a total of 374 articles were read as full text (24 reviews, 301 cross-sectional studies, 42 cohort studies, and 7 case-control studies). However, from 49 case-control and cohort studies, only 25 adequately reported risk ratios. Using the findings from these studies, positive causal associations were found for various hearing-related factors (i.e., unspecified hearing loss, sensorineural hearing loss, occupational noise exposure, ototoxic platinum therapy, and otitis media). Evidence was also found for a number of non-otological risk factors including temporo-mandibular joint disorder, depression, chronic obstructive pulmonary disease, and hyperlipidemia. Negative associations indicating preventative effects were found for diabetes and high alcohol consumption. No associations were found for low alcohol consumption, body mass index, head injury, heart failure, hypertension, leisure noise exposure, migraine, rheumatoid arthritis, sex, smoking, stroke, and whiplash. However, with the exception of unspecified hearing loss, these findings resulted from pooling no more than 4 studies, illustrating that the vast majority of the associations still remain inconclusive. CONCLUSIONS: These systematic review and meta-analysis confirm a number of otological and non-otological risk factors for tinnitus. By highlighting major gaps in knowledge, our synthesis can help provide direction for future research that will shed light on the pathophysiology, improve management strategies, and inform more effective preventions.

Using coding and non-coding rare variants to target candidate genes in patients with severe tinnitus.

Tinnitus is the phantom percept of an internal non-verbal set of noises and tones. It is reported by 15% of the population and it is usually associated with hearing and/or brain disorders. The role of structural variants (SVs) in coding and non-coding regions has not been investigated in patients with severe tinnitus. In this study, we performed whole-genome sequencing in 97 unrelated Swedish individuals with chronic tinnitus (TIGER cohort). Rare single nucleotide variants (SNV), large structural variants (LSV), and copy number variations (CNV) were retrieved to perform a gene enrichment analysis in TIGER and in a subgroup of patients with severe tinnitus (SEVTIN, n = 34), according to the tinnitus handicap inventory (THI) scores. An independent exome sequencing dataset of 147 Swedish tinnitus patients was used as a replication cohort (JAGUAR cohort) and population-specific datasets from Sweden (SweGen) and Non-Finish Europeans (NFE) from gnomAD were used as control groups. SEVTIN patients showed a higher prevalence of hyperacusis, hearing loss, and anxiety when they were compared to individuals in the TIGER cohort. We found an enrichment of rare missense variants in 6 and 8 high-constraint genes in SEVTIN and TIGER cohorts, respectively. Of note, an enrichment of missense variants was found in the CACNA1E gene in both SEVTIN and TIGER. We replicated the burden of missense variants in 9 high-constrained genes in the JAGUAR cohort, including the gene NAV2, when data were compared with NFE. Moreover, LSVs in constrained regions overlapping CACNA1E, NAV2, and TMEM132D genes were observed in TIGER and SEVTIN.

Global Prevalence and Incidence of Tinnitus: A Systematic Review and Meta-analysis.

Importance: To date, no systematic review has taken a meta-analytic approach to estimating the prevalence and incidence of tinnitus in the general population. Objective: To provide frequency estimates of tinnitus worldwide. Data Sources: An umbrella review followed by a traditional systematic review was performed by searching PubMed-MEDLINE and Embase from inception through November 19, 2021. Study Selection: Research data from the general population were selected, and studies based on patients or on subgroups of the population with selected lifestyle habits were excluded. No restrictions were applied according to date, age, sex, and country. Data Extraction and Synthesis: Relevant extracted information included type of study, time and location, end point, population characteristics, and tinnitus definition. The study followed the Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guideline. Main Outcomes and Measures: Pooled prevalence estimates of any tinnitus, severe tinnitus, chronic tinnitus, and diagnosed tinnitus as well as incidence of tinnitus were obtained using random-effects meta-analytic models; heterogeneity between studies was controlled using the χ2 test, and inconsistency was measured using the I2 statistic. Results: Among 767 publications, 113 eligible articles published between 1972 and 2021 were identified, and prevalence estimates from 83 articles and incidence estimates from 12 articles were extracted. The pooled prevalence of any tinnitus among adults was 14.4% (95% CI, 12.6%-16.5%) and ranged from 4.1% (95% CI, 3.7%-4.4%) to 37.2% (95% CI, 34.6%-39.9%). Prevalence estimates did not significantly differ by sex (14.1% [95% CI, 11.6%-17.0%] among male individuals; 13.1% [95% CI, 10.5%-16.2%] among female individuals), but increased prevalence was associated with age (9.7% [95% CI, 7.4%-12.5%] among adults aged 18-44 years; 13.7% [95% CI, 11.0%-17.0%] among those aged 45-64 years; and 23.6% [95% CI, 19.4%-28.5%] among those aged ≥65 years; P < .001 among age groups). The pooled prevalence of severe tinnitus was 2.3% (95% CI, 1.7%-3.1%), ranging from 0.5% (95% CI, 0.3%-0.7%) to 12.6% (95% CI, 11.1%-14.1%). The pooled prevalence of chronic tinnitus was 9.8% (95% CI, 4.7%-19.3%) and the pooled prevalence of diagnosed tinnitus was 3.4% (95% CI, 2.1%-5.5%). The pooled incidence rate of any tinnitus was 1164 per 100 000 person-years (95% CI, 479-2828 per 100 000 person-years). Conclusions and Relevance: Despite the substantial heterogeneity among studies, this comprehensive systematic review on the prevalence and incidence of tinnitus suggests that tinnitus affects more than 740 million adults globally and is perceived as a major problem by more than 120 million people, mostly aged 65 years or older. Health policy makers should consider the global burden of tinnitus, and greater effort should be devoted to boost research on tinnitus.

Sex Differences in Comorbidity Combinations in the Swedish Population.

High comorbidity rates, especially mental-physical comorbidity, constitute an increasing health care burden, with women and men being differentially affected. To gain an overview of comorbidity rates stratified by sex across a range of different conditions, this study examines comorbidity patterns within and between cardiovascular, pulmonary, skin, endocrine, digestive, urogenital, musculoskeletal, neurological diseases, and psychiatric conditions. Self-report data from the LifeGene cohort of 31,825 participants from the general Swedish population (62.5% female, 18-84 years) were analyzed. Pairwise comorbidity rates of 54 self-reported conditions in women and men and adjusted odds ratios (ORs) for their comparison were calculated. Overall, the rate of pairwise disease combinations with significant comorbidity was higher in women than men (14.36% vs. 9.40%). Among psychiatric conditions, this rate was considerably high, with 41.76% in women and 39.01% in men. The highest percentages of elevated mental-physical comorbidity in women were found for musculoskeletal diseases (21.43%), digestive diseases (20.71%), and skin diseases (13.39%); in men, for musculoskeletal diseases (14.29%), neurological diseases (11.22%), and digestive diseases (10%). Implications include the need for integrating mental and physical health care services and a shift from a disease-centered to an individualized, patient-centered focus in clinical care.

The Impact of COVID-19 Confinement on Tinnitus and Hearing Loss in Older Adults: Data From the LOST in Lombardia Study.

Background: Although a direct relationship between tinnitus or hearing difficulties and COVID-19 has been suggested, current literature provides inconsistent results, and no research has been undertaken in older adults. Methods: In November 2020, we conducted the LOST in Lombardia survey, a telephone-based cross-sectional study on a sample of 4,400 individuals representative of the general population aged ≥65 years from Lombardy region, Northern Italy. Individuals with diagnosed tinnitus and/or hearing loss were asked whether their conditions had improved or deteriorated in 2020 compared to 2019. Results: Overall, 8.1% of older adults reported a diagnosis of tinnitus and 10.5% of hearing loss. In 2020 compared to 2019, among individuals with tinnitus, those with increasing severity (5.0%) were similar to those decreasing it (5.3%). Among individuals with hearing loss, more people reported an increase (13.6%) than a decrease (3.2%) in their disease severity. No individual with a diagnosis in 2020 of tinnitus (n = 6) or hearing loss (n = 13) had COVID-19. The incidence of tinnitus was lower in 2020 (rate: 14.8 per 10,000 person-years) than in previous years (rate in 1990-2019: 36.0 per 10,000 person-years; p = 0.026). There was no change in the incidence of hearing loss (p = 0.134). Conclusions: In this large representative sample of older adults, on average neither COVID-19 confinement nor SARS-CoV-2 infection appeared to increase the severity or incidence of tinnitus. The increased severity of hearing difficulties may totally or partially be explained by physiologic deterioration of the condition, or by a misperception due to the use of face-masks.