Inflammatory Biomarkers and Tinnitus in Older Adults

Abstract

Background:

Tinnitus refers to a common disorder affecting older adults frequently. This condition can disturb mental health and psychological well-being and contribute to cognitive decline. Despite recent advances in research, its pathophysiology remains incompletely understood. Therefore, this study aimed to investigate the sensation of tinnitus, its consequences on the quality of life of older adults, and its correlation with cytokine levels.

Methods and material:

This cross-sectional study included a sample of 103 independent older adults. Information regarding clinical history, tinnitus, and hearing loss was obtained through interviews. Assessment of tinnitus intensity and resulting impairments was conducted using Visual Analogue Scale (VAS) and Tinnitus Handicap Index (THI), respectively. Subjects underwent audiological evaluation and were measured for inflammatory markers. Statistical analyses included chi-square, Mann–Whitney, and Kruskal–Wallis tests and calculation of the effect size (Φ).

Results:

The condition of older adults with tinnitus (51.5%) was associated with hearing loss and previous noise exposure. No differences were observed in the cytokines between groups with and without tinnitus (P > 0.05), whereas a difference was found in the interleukin-10 (IL-10) of the male group (P = 0.016; r = 0.69). In those with tinnitus, VAS had a median and (interquartile range) of 5 (2–7), and the values were 21 (10–38) for THI. In addition, VAS and minimum masking level exhibited a significant correlation with IL-6 (P = 0.018; rs = 0.335) and IL-2 (P = 0.035; rs = 0.299), respectively. Furthermore, the groups with intense and mild VAS presented different levels of tumour necrosis factor alpha (TNF-α) (P = 0.041; E²_R = 0.12).

Conclusion:

The results reveal an association between tinnitus and hearing loss and previous noise exposure. Moreover, increased sound-masking levels and VAS correlated with IL-2 and IL-6, respectively. TNF-α levels varied between the mild and intense VAS groups.

KEY MESSAGES:

• (1)Aging and its related diseases share overlapping mechanisms and generate chronic and insidious inflammation, which may significantly increase morbidity and mortality. Identifying the mechanisms of aging-related inflammation is crucial to investigating the benefits of treatments that modulate inflammation in this population.
• (2)There is evidence that interleukins can act as possible tinnitus biomarkers.
• (3)The results of this study demonstrate that inflammatory mechanisms are involved in tinnitus pathophysiology.
• (4)Tinnitus Handicap Inventory (THI) and Visual Analogue Scale (VAS) do not require authorisation.
• (5)The THI, validated for Brazilian Portuguese and used in this research, constitutes a freely accessible instrument and is available for use in scientific research.
• (6)The VAS used in the article is also made freely available and for reproducibility.

INTRODUCTION

Tinnitus refers the perception of sound in the ears or head without an external generating source. This condition forms a pathophysiological relationship with inner ear changes, with multiple potential causes.[1] The worldwide prevalence of tinnitus reaches 15%, and among adults, 10–20% perceive tinnitus as a stressor.[2] Tinnitus can affect cognition, psychological well-being and mental health and hinder daily living activities.[3,4] This symptom is expected to increasingly affect older populations. Hence, as a result of poor adaptation to ageing, these individuals experience decreased cellular function, physical ability and adaptability to the environment.[5]

Tinnitus is strongly related to acquired hearing loss.[6] In addition, the inflammatory process contributes to the development of deafness[6] given that proinflammatory cytokines, for example, tumour necrosis factor alpha (TNF-α), interleukin 1 alpha (IL-1α), IL-2 and nuclear factor kappa beta, can infiltrate inner ear cells.[7] Therefore, ageing-related inflammation may considerably influence the appearance of otoneurologic symptoms such as tinnitus.

The current management of tinnitus is based on a multidisciplinary approach aimed at reducing its perception or the development of new coping strategies.[8] Consequently, investigations focusing on whether inflammatory mechanisms are involved in the origin of symptoms can be crucial for the development of new treatments. This study aimed to investigate the sensation of tinnitus, its consequences on the quality of life of older adults and its correlation with pro- and anti-inflammatory ILs.

MATERIALS AND METHODS

Study design, location and population

This cross-sectional study was conducted in collaboration with Unopar University as part of a broader research initiative launched in 2018, titled Active Ageing. The study involved a sample of 103 older adults from Londrina, Brazil, and was carried out by an interdisciplinary team of researchers from various health fields, including medicine, audiology, nursing, pharmacy, and public health. The primary aim of the project was to analyse the relationship between health status, lifestyle, and subjective aspects of ageing. Older adults were recruited through the city’s media, social networks, pamphlets and sampling techniques among family members for inclusion in an initial convenience sample. All participants were previously informed regarding the research objectives and evaluation procedures and agreed to sign an informed consent form. The study was approved by the Research Ethics Committee of the Universidade Estadual de Londrina, under protocol number CAAE: 92480418.8.0000.5231.

Inclusion and exclusion criteria

The inclusion criteria were independent older adults aged 60 years or above, of both sexes, classified at level 3 of physical function as proposed by Spirduso,[9] can comprehend speech and answer questionnaires, who signed an informed consent form, filled in medical history questionnaires and agreed to collection of blood samples for cytokine count. The exclusion criteria were as follows: participation in supervised exercise programmes in the previous three months, having a disease or limitation that can hinder their participation in tests, for example, physical or mental disability, decompensated respiratory or cardiac diseases, neurological, vestibular, orthopaedic, cardiovascular or psychiatric diseases, chronic infection, tumours and recent surgeries, that can interfere with the evaluations and affect the production of inflammatory factors. With the use of GPower 3.1.9.2 software for Windows[10] (Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany), sample size calculation was based on data from a study developed with another older population a priori for two-tailed bivariate correlation, with ρ H1 (alternative hypothesis) = 0.5,[11] α = 0.05 and 95% power analysis. Finally, 46 participants with tinnitus were included in the study.

Clinical information and study variables

In accordance with the inclusion and exclusion criteria, 103 older adults were evaluated and had their blood samples collected. Six adult participants failed to complete the tinnitus assessments and were excluded from the sample. The participants were divided into two groups: one with reported tinnitus (n = 50) and the other without tinnitus (n = 47).

In accordance with the Miller protocol,[12] the patients’ clinical information was collected from routine care at the Speech-Language-Hearing Clinic (Audiology department − Unopar University) for hearing assessment and investigation. All participants were interviewed to gather general information regarding their personal clinical history. They also answered questionnaires on demographic data and auditory and clinical characteristics (previous and present diseases, self-reported hearing loss and noise exposure). Older adults who reported tinnitus were assessed to detect the presence of tinnitus sensation, the presence of ear tinnitus, the frequency of sensation, symptom onset and the type of tinnitus.

The patients were instructed to report the intensity of their perceived tinnitus on the Visual Analog Scale (VAS), which is generally used to measure tinnitus distress levels. The VAS includes a 10 cm straight line, which indicates the absence of symptoms at one end and the most serious tinnitus condition at the other end.[13] The perceived symptom of tinnitus was graded from 0 to 10, in which 0 represented the minimum and 10 represented the maximum intensity of tinnitus perceived by older adults.[14] The quantified results of VAS were divided as follows: mild (0–3), moderate (4–7) and severe (8–10).[15]

In addition, Tinnitus Handicap Inventory (THI) was used to assess the level of impairment caused by tinnitus on the patient’s quality of life, with a version adapted to Brazilian Portuguese.[16] Scored from 0 to 100, THI includes 25 questions that evaluate the self-perceived disabling effects of tinnitus: 11 questions on functional aspects, 9 on emotional aspects and 5 on catastrophic aspects. The interviewer read the questions aloud, and the respondents answered “Yes”, “Sometimes” or “No”. The score was calculated as follows: “Yes”, 4 points; “Sometimes”, 2 points; “No”, 0 point. Tinnitus annoyance was classified based on the total Brazilian THI score: slight (0–16), mild (18–36), moderate (38–56), severe (58–76) or catastrophic (78–100).[15]

The patients subjected also participated in a pure-tone audiometry in a sound booth to establish their hearing thresholds. Initially, impediments to audiological assessment were ruled out through inspection of the external auditory meatus. Katz[12] protocol served as a basis when the participants reported their audiological medical history and were assessed via pure-tone audiometry (at 250–8000 Hz for air conduction and 500–4000 Hz for bone conduction).

After audiometric testing, tinnitus pitch and loudness matching of patients were conducted to assess their psychoacoustic tinnitus acuphenometry, which verified the frequency and loudness of the perceived tinnitus. The frequency was assessed by checking the proximity of tinnitus to pure tone or noise and then presenting it at 250–8000 Hz to the ear of the respondents without the referred sound. The respondents were then instructed to indicate the sound closest to their tinnitus. The intensity was measured by gradually increasing the loudness from a level near the hearing threshold at the frequency identified in the initial test, until it closely matched the perceived tinnitus. The minimum masking level (MML) was then determined by applying ascending narrowband noise until the subject could no longer perceive the tinnitus. Residual inhibition was measured in the ear with tinnitus, presenting the previous 10 dB noise above the MML for 1 minute. This examination included four categories: complete, partial, negative inhibition and rebound effect (when tinnitus became louder).

Cytokine serum levels were measured via the cytometric bead array (CBA), which is an application of flow cytometry that enables the simultaneous quantitative evaluation of several proteins.[17] Research on the levels of IL-2, IL-4, IL-6, IL-10, interferon-gamma (IFN-γ) and TNF-α was carried out using the Th1/Th2 kit (IL-2, IL-4, IL-6, IL-10, IFN-γ and TNF-α − BD Pharmingen, (10975 Torreyana Rd, San Diego, CA, 92121, USA). The experiment followed the protocol described by Mitelman et al.,[18] which involved the conjugation of six bead samples with different fluorescence intensities with a capture antibody specific for each cytokine to form CBA; the results were read on a BD Accuri C6 flow cytometer® (BD Biosciences, 2350 Qume Dr, San Jose, CA, 95131, USA). Bead samples were visualised based on their fluorescence intensities. CBA was completed through mixing of cytokine capture beads with a detection antibody conjugated to fluorochrome phycoerythrin (PE) and their incubation with the samples.

Acquisition tubes containing 50 μL sample, 50 μL bead mix and 50 μL Th1/Th2 PE detection reagent (Human Th1/Th2 PE Detection Reagent/1 vial, 4 mL) were prepared. The standard curve was obtained via the same procedure. The tubes were homogenised and incubated for 3 hours at room temperature in the dark. The samples were analysed via flow cytometry, and the results, which are presented in graphs and tables in Figure 1, were generated using FCAP Array v.3 software (Soft Flow Hungary Ltd, 91/B, Pellérdi út. H-7634, Pécs Hungary), with cytokine levels expressed in pg/mL.

Figure 1.

Distribution of six bead populations as a function of their various fluorescence intensities. Source: The author. Figure generated using FCAP Array v.3 software (Soft Flow Hungary Ltd, 91/B, Pellérdi út. H-7634, Pécs Hungary).

Statistical analyses

SPSS (Statistical Package for the Social Sciences), (IBM Corporation Business Analytics Software, Rua Tutóia, 1157, São Paulo, 04007-900, Brasil), version 20 for Windows was used for statistical analyses. Kolmogorov–Smirnov and Shapiro–Wilk tests did not find data normality. Hence, nonparametric tests were performed with 95% confidence intervals. The Mann–Whitney effect size was calculated as r = Z/√n and used to verify the differences between groups with and without tinnitus and continuous variables, which include age and cytokines.[19,20] Differences between groups categorised by VAS and cytokines were verified using the Kruskal–Wallis effect size, with the estimated epsilon-square (E²_R) computed using the equation E²_R = H/(n2–1)/(n + 1).[19] In all tests, the effect size was classified in accordance with the work of Cohen [21]. Spearman’s correlation was determined to assess the correlation between the VAS score and cytokines, between THI and cytokines, between pitch and between loudness and masking, following the classifications reported by Portney and Watkins [22]. Chi-square test was conducted to verify the associations between categorical variables, which had a degree of freedom equal to one. The effect size y (Φ) was calculated in SPSS.

RESULTS

A total of 103 older adults who agreed to have their blood samples collected were assessed. However, six adult participants failed to complete the tinnitus assessments and were excluded from the sample. As a result, 97 participants with a mean age of 70.6 ± 7.7 years were included in the analysis. Among the participants, 87.6% (n = 85) were female, and 12.4% (n = 12) were male; 70.2% (n = 70) had hearing loss, and 51.5% (n = 50) reported tinnitus. In those with tinnitus, the median and (interquartile range) were obtained as follows: VAS = 5 (5–7), THI = 21 (10–38), pitch (Hz) = 2000 (1000–3000), loudness (dBSL) = 50 (30–60), MML (dBSL) = 55 (40–70). THI was used to classify tinnitus as follows: slight (46%; n = 23), mild (28%; n = 14), moderate (20%; n = 10), severe (4%; n = 2) and catastrophic (2%; n = 1).

Table 1 shows the association of tinnitus with hearing loss (P = 0.007; Φ = 0.272) and previous noise exposure, with P < 0.05 (P = 0.049; Φ = 0.202). The groups with and without tinnitus showed no differences in terms of cytokines or age (P > 0.05). Table 2 provides the results on subgroup analyses for sex. Mann–Whitney test with an exact P-value revealed differences and a medium effect for in the male group IL-10 (P = 0.016; r = 0.69); those with tinnitus attained lower values.

Table 1.

Statistical analysis between groups with and without tinnitus

Variables	No tinnitus (n = 47)	Tinnitus (n = 50)	P-value effect size
Sex
Female	43 (91.5%)†	42 (84%)	P = 0.263‡
Male	4 (8.5%)	8 (16%)	Φ = 0.114§
Age range (years)
60–70	25 (53.2%)	27 (54%)	P = 0.936
71–90	22 (46.8%)	23 (46%)	Φ = −0.008
Previous exposure to noise
No	37 (78.7%)	30 (60%)	P = 0.049*
Yes	10 (21.3%)	20 (40%)	Φ = 0.202
Hearing loss (right ear)
No	19 (40.4%)	8 (16%)	P = 0.007*
Yes	28 (59.6%)	42 (84%)	Φ = 0.272
Age	70 (63–77)||	65 (64–75)	P = 0.803¶r = 0.02#
IFN-γ (pg/mL)	1.52 (0.0–18.71)	5.68 (0.0–15.16)	P = 0.827r = 0.02
TNF-α (pg/mL)	1.34 (0.0–5.85)	0.23 (0.0–6.23)	P = 0.613r = 0.05
IL-10 (pg/mL)	0.77 (0.0–2.74)	0.79 (0.0–3.74)	P = 0.903r = 0.01
IL-6 (pg/mL)	2.10 (0.68–6.20)	1.20 (0.18–3.52)	P = 0.106r = 0.16
IL-4 (pg/mL)	0.0 (0.0–3.15)	0.0 (0.0–1.85)	P = 0.544r = 0.06
IL-2 (pg/mL)	0.0 (0.0–4.92)	0.0 (0.0–6.88)	P = 0.536r = 0.06

IFN-γ = interferon gamma; TNF-α = tumour necrosis factor alpha; IL-10, IL-6, IL-4 and IL-2 = interleukins-10, −6, −4, and −2, respectively. †Absolute and (relative frequencies). ‡P-value for Chi-square test. §Letter phi, indicates effect size for Chi-square test for Table 2 × 2. ||Median and interquartile range (25–75%). ¶P-value for Mann–Whitney test. #Effect size for Mann–Whitney test. ^*Statistically significant.

Table 2.

Levels of proinflammatory and anti-inflammatory cytokines divided by gender.

	Female			Male
	No tinnitus(n= 43)	Tinnitus(n = 42)	P-valueeffect size(Mann–Whitney test)	No tinnitus(n= 4)	Tinnitus(n= 8)	P-value†effect size(Mann–Whitney test)
IFN-γ(pg/mL)	1.92 (0.0–18.71)‡	6.21 (0.0–16.17)	P = 0.700r = 0.04	0.0 (0.0–24.09)	0.96 (0.0–5.96)	P = 0.808r = 0.10
TNF-α(pg/mL)	1.01 (0.0–4.95)	1.91 (0.0–6.32)	P = 0.770r = 0.03	5.14 (0.50–8.66)	0.0 (0.0–0.34)	P = 0.073r = 0.60
IL-10(pg/mL)	0.58 (0.0–2.55)	1.05 (0.0–4.00)	P = 0.431r = 0.08	5.09 (2.32–6.24)	0.71 (0.0–1.74)	P = 0.016*r = 0.69
IL-6(pg/mL)	2.10 (0.68–6.20)	1.32 (0.25–3.59)	P = 0.218r = 0.13	3.12 (0.46–8.88)	0.83 (0.0–2.92)	P = 0.283r = 0.32
IL-4(pg/mL)	0.0 (0.0–2.73)	0.0 (0.0–1.86)	P = 0.840r = 0.02	2.80 (0.0–7.48)	0.0 (0.0–2.14)	P = 0.368r = 0.35
IL-2(pg/mL)	0.0 (0.0–4.14)	0.0 (0.0–5.48)	P = 0.769r = 0.03	3.20 (0.0–8.61)	4.62 (0.36–8.18)	P = 0.683r = 0.14

IFN-γ = interferon gamma; TNF-α = tumour necrosis factor alpha; IL-10, IL-6, IL-4 and IL-2: = interleukin-10, −6, −4 and −2, respectively. †Exact P-value demonstrated. ‡Median and interquartile range (25–75%). *Statistically significant.

Figures 2 and 3 illustrate the significant Spearman’s correlation between VAS and IL-6 (P < 0.05, P = 0.018, rs = 0.335), as well as between MML and IL-2 (P = 0.035, rs = 0.299). Both correlations were classified as weak, while all other correlations showed P>0.05. Figure 4 presents representative dot plots of the standard values for each cytokine.

Figure 2.

Spearman’s correlation of IL-6 and VAS (n = 50). IL-6 = interleukin-6; VAS = visual analogue scale. *Statistically significant. Source: The author. Figure generated using Microsoft® Excel version 16.83 (Microsoft Corporation, One Microsoft Way, Redmond, WA 98052, United States).

Figure 3.

Spearman’s correlation of IL-2 and MML (n = 50). IL-2 = interleukin 2; MML = minimum masking level. *Statistically significant. Source: The author. Figure generated using Microsoft® Excel version 16.83 (Microsoft Corporation, One Microsoft Way, Redmond, WA 98052, United States).

Figure 4.

Representative dot plots of cytokine standards. Source: The author. Figure generated using FCAP Array v.3 software (Soft Flow Hungary Ltd, 91/B, Pellérdi út. H-7634, Pécs Hungary).

Cytokine levels were compared across VAS and THI categories. In the VAS analysis, pairwise comparisons revealed a significant difference in TNF-α between the intense and mild groups, with the intense group showing higher levels (P = 0.041; E2R = 0.12), although the effect size was small [Table 3]. No significant differences were observed across THI categories or in residual inhibition (P > 0.05; data not shown in tables).

Table 3.

Comparative analysis between VAS categorical and cytokines

	Mild (n = 22)	Moderate (n = 24)	Intense (n = 4)	P-value†effect size (Kruskal–Wallis)
IFN-γ(pg/mL)	4.28 (0.0–13.53)‡	5.68 (0.0–18.30)	4.14 (0.0–12.91)	P = 0.699E2R = 0.01
TNF-α(pg/mL)	0.0 (0.0–4.48)	0.0 (0.0–5.82)	6.51 (5.06–11.03)	P = 0.041*E2R = 0.12
IL-10(pg/mL)	0.71 (0.0–3.2)	0.81 (0.0–3.96)	2.68 (0.05–6.96)	P = 0.742E2R = 0.01
IL-6(pg/mL)	0.91 (0.0–1.31)	1.91 (0.25–3.56)	3.19 (1.27–5.04)	P = 0.053E2R = 0.11
IL-4(pg/mL)	0.0 (0.0–1.59)	0.31 (0.0–2.47)	0.90 (0.0–4.26)	P = 0.419E2R = 0.03
IL-2(pg/mL)	0.0 (0.0–7.28)	0.57 (0.0–6.40)	3.16 (0.0–7.72)	P = 0.972E2R = 0.01

IFN-γ = interferon gamma; TNF-α = tumour necrosis factor alpha; IL-10, IL-6, IL-4 and IL-2: interleukin-10, −6, −4 and = -2, respectively. †Exact P-value demonstrated. ‡Median and interquartile range (25–75%). *Statistically significant.

DISCUSSION

Among the population, 51.5% of participants (n = 50) reported tinnitus. A widespread difficulty has been observed in the reporting of tinnitus, which led to varied definitions between studies and group heterogeneity. A systematic review[23] stated that the prevalence of tinnitus increases from 5.1% to 42.7% with age. Regarding tinnitus intensity and degree of discomfort, the mean VAS was 5 (5), and the mean total THI was 21 (28). Most of the patients (74%) achieved slight-to-mild scores in THI, which indicates that tinnitus was causing discomfort to the assignments.

The relationship among tinnitus, hearing loss and noise exposure is widely recognised. Subjective tinnitus can be attributed to presbycusis and noise-induced hearing loss.[23] Kang et al. associated the degree of hearing loss with loud tinnitus noises.[24] The present study revealed an association between tinnitus and hearing loss (P = 0.007; Φ = 0.272) and between tinnitus and previous noise exposure (P = 0.049; Φ = 0.202).

Interleukins may serve as potential biomarkers for tinnitus.[25] In experimental studies, mice exposed to noise or treated with salicylate to induce tinnitus demonstrated a significant association between tinnitus and elevated levels of proinflammatory cytokines, particularly TNF-α and IL-1β.[26,27,28,29] Conversely, IFN-γ gene expression decreased, while IL-6 gene expression remained unchanged.[30] Treatments that reduced TNF-α expression not only mitigated neuroinflammation but also improved the behavioural phenotype of rats associated with tinnitus.[27]

No differences were observed between cytokine levels in groups with and without tinnitus. Such a result was observed possibly because the studied group of older adults practice physical activities that can reduce the levels of proinflammatory ILs and tinnitus.

A number of studies compared the levels of inflammatory markers between groups with and without tinnitus. Weber et al. observed a decrease in TNF-α levels and an improvement in tinnitus disturbance after relaxation treatment;[31] Haider et al. reported significantly lower levels of IL-10 in the group without tinnitus.[32] Our work revealed differences and a medium effect on IL-10 (P = 0.016; r = 0.69) in the male group; those with tinnitus had lower values. IL-10 is the most critical cytokine in the suppression of proinflammatory responses, and it plays an important role as a negative regulator of immune responses to microbial antigens. This cytokine also prevents excessive inflammation during infection.[33]

Cytokines IL-2, IL-6 and TNF-possess proinflammatory characteristics. IL-2 has dual opposing functions: stimulation of conventional T cells to promote immune responses and maintenance of regulatory T cells to control this process.[34] IL-6 is a multifunctional and pleiotropic cytokine that regulates immune response and acute-phase inflammatory response, host defence and cell growth. This biomarkers belong to the main signalling pathways that modulate the relationship between ageing and chronic inflammation.[35] TNF-α is an inflammatory response regulator that plays an important role in the normal response to infection; however, its inadequate or excessive production can damage tissues via chronic inflammation.[36] Experimental studies in rats demonstrated the in vivo production of TNF-α, IL-1β and IL-6 in inflamed inner ears, along with leukocyte infiltration; others reported that TNF-α aggravated cochlear inflammation.[37]

Despite the lack of difference between tinnitus and cytokine levels, VAS exhibited a significant correlated with IL-6 (P = 0.018; rs = 0.335). TNF-α levels varied in terms of the VAS between the mild and intense groups, with a small effect size. These findings imply that the greater the tinnitus intensity, the higher the IL-6 and TNF-α levels. Moreover, the correlation between MML and IL-2 (P = 0.035; rs = 0.299) demonstrated that the higher sound intensity necessary to mask tinnitus and the higher the IL-2 levels. Haider et al. revealed that individuals with a negative or rebound effect of residual inhibition possess higher levels of IL-2 than those with partial or complete inhibition.[32] The THI categories and residual showed no inhibition.

The results revealed the pathological and physiological mechanisms of tinnitus through the analysis of its relationship with hearing loss, noise exposure, and inflammatory mechanisms. This indicates the important role of the inflammatory mechanism in tinnitus development and provides new insights into additional investigation research on the aetiology and treatment of this condition. Moreover, a correlation was discovered between the severity of tinnitus and cytokine levels, which suggests a possible role of cytokines in the pathogenesis of tinnitus. This finding is important for deepening our understanding of the aetiology of tinnitus and developing targeted treatment plans. Therefore, this study not only enriches the theoretical foundation of tinnitus but also provides valuable guidance for its clinical practice in treatment.

Finally, further studies are urgently needed to the plasmatic levels of cytokines, which must be linked to the susceptibility to tinnitus in younger populations and reach a conclusion regarding the relationship between ILs and tinnitus. Such findings may aid otolaryngologists and audiologists in identifying risk factors in people with tinnitus and develop potential research areas on biological changes related to tinnitus onset and permanence. Further research on inflammatory biomarkers may aid in the development of interventions to modulate cytokine activities. Given that neuroinflammation may be a response of the central nervous system to injury, infection and abnormal neural activities, efforts, such as controlling acute inflammatory response via specialised proinflammatory mediators, may provide insights into the prevention and treatment of tinnitus-related inflammatory processes.[38]

The limitations of the study include the heterogeneity between sexes in the sample, which calls for further studies involving larger populations and different ethnicities for confirmation. Furthermore, the quantification of cytokine levels in tinnitus patients may also help in comprehending individual inflammation variabilities that result in this symptom. In addition to the measurement of cytokines in body fluids, cells and tissues provide essential information that contributes to understanding the disease process and in designing the treatment strategies. However, various factors, such as short half-life and low plasma concentrations, still pose a challenge and thus need to be addressed.

CONCLUSION

The findings of this study reveal an association between tinnitus and hearing loss and previous noise exposure. Moreover, increased sound-masking levels and VAS correlated with IL-2 and IL-6, respectively. TNF-α levels varied between the mild and intense VAS groups. Future research should explore the role of inflammatory mechanisms in tinnitus and the specific relationship between cytokines and tinnitus to provide more effective treatment options for tinnitus patients.

Financial support and sponsorship

This work was supported by the PROEXT- Programa de Extensão Universitária − Ministério da Educação − Brazil; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) − Brazil − Finance Code 001;

Conflicts of interest

No potential conflict of interest was reported by the authors. All authors certify that they have no affiliations with or involvement in any organisation or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.

The data that support the findings of this study are available on request from the corresponding author, Tanaka LS. The data are not publicly available due to containing information that could compromise the privacy of research participants.

Ethics approval

CAAE: 92480418.8.0000.5231.

Institution: Universidade Estadual de Londrina − UEL.