Effects of serum zinc level on tinnitus




Abstract


Objective


The aim of this study was to assess zinc levels in tinnitus patients, and to evaluate the effects of zinc deficiency on tinnitus and hearing loss.


Methods


One-hundred patients, who presented to an outpatient clinic with tinnitus between June 2009 and 2014, were included in the study. Patients were divided into three groups according to age: Group I (patients between 18 and 30 years of age); Group II (patients between 31 and 60 years of age); and Group III (patients between 61 and 78 years of age). Following a complete ear, nose and throat examination, serum zinc levels were measured and the severity of tinnitus was quantified using the Tinnitus Severity Index Questionnaire (TSIQ). Patients were subsequently asked to provide a subjective judgment regarding the loudness of their tinnitus. The hearing status of patients was evaluated by audiometry and high-frequency audiometry. An average hearing sensitivity was calculated as the mean value of hearing thresholds between 250 and 20,000 Hz. Serum zinc levels between 70 and 120 μg/dl were considered normal. The severity and loudness of tinnitus, and the hearing thresholds of the normal zinc level and zinc-deficient groups, were compared.


Results


Twelve of 100 (12%) patients exhibited low zinc levels. The mean age of the zinc-deficient group was 65.41 ± 12.77 years. Serum zinc levels were significantly lower in group III ( p < 0.01). The severity and loudness of tinnitus were greater in zinc-deficient patients ( p = 0.011 and p = 0.015, respectively). Moreover, the mean thresholds of air conduction were significantly higher in zinc-deficient patients ( p = 0.000).


Conclusion


We observed that zinc levels decrease as age increases. In addition, there was a significant correlation between zinc level and the severity and loudness of tinnitus. Zinc deficiency was also associated with impairments in hearing thresholds.


1


Introduction


Tinnitus refers to the sensation of hearing sounds without any external source. It affects 17% of the general population, and 33% of older adults . Although tinnitus can manifest at any age, it is more common in adults between 40 and 80 years of age . Tinnitus is usually accompanied by hyperacousis or hearing loss. The cause of tinnitus may be oncological (e.g., hearing loss, noise trauma, Meniere’s disease, acoustic neurinoma, or ototoxic medications or substances), neurological (e.g., multiple sclerosis or head injury), metabolic (e.g., thyroid disorder, hyperlipidemia, or vitamin B12 deficiency), or psychogenic (e.g., depression, anxiety, or fibromyalgia) . Despite the suspected involvement of many factors, the physiopathology of tinnitus remains poorly characterized. Zinc deficiency is considered as a possible etiology .


Zinc is a trace element with an important role in metabolism. It is an antioxidant which facilitates toxin elimination, and is also a co-factor in many enzymes. Zinc deficiency is associated with impaired immune response, delayed wound healing, deficiencies in taste, olfactory function and neurophysiological responses, and retarded motor development . Levels of zinc in the cochlea are higher compared with other areas: zinc has a role in cochlear function in the cochlear nucleus, in addition to neuronal function, such that zinc deficiency could cause tinnitus and hearing loss .


This study aims to assess the prevalence of zinc deficiency in patients with tinnitus, and evaluate its effects on tinnitus and hearing.




2


Material and methods


2.1


Study population


Ethical approval for the study was granted by the Ethics Committee of the Okmeydani Training and Research Hospital. One-hundred patients, who presented to an outpatient clinic with tinnitus between June 2009 and 2014 were included. The age of all patients, and the duration of, and any fluctuations in, their tinnitus, and their noise exposure and drug use histories, were obtained.


All patients underwent complete otorhinolaryngologic and audiometric evaluations, complete blood count assessment, and thyroid function and biochemical tests. Patients who had experienced tinnitus for at least 6 months were included. Presbycusis, neurological disease, acoustic neuromas or glomus tumors, chronic otitis media, otosclerosis, active Meniere’s disease, and sudden idiopathic hearing loss were the exclusionary criteria, in addition to the use of psychotropic drugs, antidepressants, anticonvulsants and tranquilizers. Patients who were above 65 years and had symmetrical increase in hearing threshold was accepted presbycusis. Patients were divided into three groups according to age, as follows: Group I (patients between 18 and 30 years of age); Group II (patients between 31 and 60 years of age); and Group III (patients between 61 and 78 years of age).


2.2


Assessment of tinnitus severity


To assess tinnitus severity, the 12-item Tinnitus Severity Index Questionnaire (TSIQ) was applied . The TSIQ employs Likert scales for questions pertaining to perceived tinnitus discomfort. The side of the head in which tinnitus was experienced (i.e., unilateral, bilateral or central), and its subjective loudness, were assessed.


Patients rated the loudness of their tinnitus on a scale ranging from 1 ( very quiet ) to 7 ( very loud ) . They were also asked whether their tinnitus was intermittent or continuous.


2.3


Serum zinc level assessment


Atomic absorption spectrophotometry was used to measure serum zinc levels. Levels between 70 and 120 μg/dl were considered normal.


2.4


Hearing level examination


Audiology and high-frequency audiology were applied to all patients. Audiometric evaluation was performed in a soundproof AC 40 audiometric cabin, calibrated according to ISO 9001 standards. Frequencies between 250 and 20,000 Hz were tested for air and bone conduction, at frequencies between 500 and 4000 Hz . The mean hearing threshold levels, in both ears of patients with and without zinc deficiency, were compared for frequencies between 250 Hz and 20,000 Hz.


2.5


Statistics


The data of this study were assessed for statistical analysis with SPSS 17.O V. Descriptive statistical methods (mean, standard deviation), as well as student-t test were used for the comparison of quantitative data showing the parameters of the normal distribution. Analysis of the variances (ANOVA) and post hoc Tukey as the comparison test were used to compare between the age groups for serum zinc levels. Significance level was set as p < 0.05.




3


Results


3.1


Study population


The mean age of the patients was 50.2 ± 13.57 years (range: 17–80 years). Fifty-eight of the 100 (58%) patients were female, and 42 (42%) were male; 37% of the patients described a “whistling”-type tinnitus, and 32% described a bell sound. The remaining patients indicated that their tinnitus was of a mixed-type. The duration of patients’ experience of tinnitus ranged between 6 and 120 months (mean = 17.59 months). Twelve patients (12%) had low serum zinc levels; the other 88 patients (88%) were characterized by normal zinc levels ( Table 1 ).



Table 1

Demographic data of tinnitus patients.




































Age (year) 17–78 Mean (50.2 ± 13.57)
Tinnitus side Right ear 22 (22%)
Left ear 21 (21%)
Bilaterally 57 (57%)
Sex Female 58 (58%)
Male 42 (42%)
Tinnitus duration (month) 6–120 Mean 17.59
Zinc Zinc deficiency n = 12 (12%)
Zinc normal n = 88 (88%)


The mean age of the patients with lower zinc levels was 65.41 ± 12.77 years, compared with 48.13 ± 12.36 years in patients with normal zinc levels. The mean serum zinc level was 64.00 ± 3.36 05 in zinc-deficient patients while it was 96.89 ± 15.11 in patients with normal zinc levels ( Table 2 ).



Table 2

Analysis of tinnitus patients.



















Zinc deficiency (n = 12) Zinc normal (n = 88)
Mean ± SD Mean ± SD
Age 48.13 ± 12.36 65.41 ± 12.77
Zinc levels 64.00 ± 3.36 96.89 ± 15.11


Analysis of zinc levels according to age revealed a significant group difference ( p < 0.001). A post-hoc Tukey test revealed that there was no difference between groups I and II ( p = 0.703), but that group III had significantly lower levels of zinc compared with both groups I and II ( p = 0.000; p = 0.000; Tables 3–4 and Fig. 1 ).


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Aug 23, 2017 | Posted by in OTOLARYNGOLOGY | Comments Off on Effects of serum zinc level on tinnitus

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