Abstract
Aim
Anaemia is a prevalent medical condition that impacts a significant proportion of the worldwide populace. While the cardiovascular and respiratory systems’ influence on anaemia has been extensively researched, its effect on the auditory system remains unclear. The objective of this investigation was to assess the pure tone audiometry of individuals with anaemia and establish a connection between the type of hearing impairment and the level of anaemia, if any.
Materials and Methods
This cross-sectional study comprised 100 patients who were diagnosed with anaemia. All study participants underwent a thorough general examination and hearing assessment, which encompassed tuning fork tests, and pure-tone audiometry. Statistical analysis was utilized to determine the type and severity of hearing loss and its correlation with the degree of anaemia.
Results
Our research findings indicate that 46.8% of moderately anaemic patients and 62.9% of patients with severe anaemia exhibited sensorineural hearing loss. A significant correlation was observed between the degree of anaemia (p < 0.05) and hearing loss. Our research findings indicate that individuals with moderate and severe anaemia exhibit a notably greater incidence of hearing impairment in comparison to those with mild anaemia.
Conclusion
The research findings thus suggest a potential correlation between anaemia and auditory impairment. The timely identification and management of anaemia could potentially play a crucial role in preventing or reducing hearing impairment among individuals with anaemia. Additional research is required to clarify the mechanisms that underlie this association and to investigate possible interventions for mitigating the risk of hearing impairment in individuals with anaemia.
Keywords: Anaemia, Tuning fork Tests, Pure tone Audiometry, Hearing loss, Hearing Impairment
Introduction
Hearing loss is more common than it used to be, affecting 40–66% of people over 65 and 80% of people over 85. [1, 2] Tobacco use, diabetes, and hypertension are risk factors for adult hearing loss that begins early. [2, 3] The major causative factors for anaemia vary with different geographical locations. Sudden sensorineural hearing loss (SNHL) is a rapid drop in hearing ability that occurs in less than 72 h. Iron deficiency anaemia is a subtype of anaemia that is distinguished by low levels of haemoglobin, ferritin, and iron in the blood as well as high amounts of soluble transferrin receptors in the patient’s blood. IDA frequently gets better when the source of blood loss is stopped and oral iron supplements are used. [4].
Although the role of iron in this region has not been fully elucidated, ischemia injury to the blood supply of the inner ear is susceptible. A vascular disease like abrupt SNHL may become worse from IDA. This is hypothesized to be brought about by cochlear defects that affect the stereocilia of the inner and outer hair cells, such as strial atrophy and reduced spiral ganglion cells [5, 6]. Due to iron’s function in the vascular and nervous systems, other common causes of adult hearing loss besides sudden SNHL may also be connected to iron. While the cardiovascular and respiratory systems’ influence on anaemia has been extensively researched, there are very few studies on the association between hearing loss and Iron deficiency anaemia in India. The aim of our study is to examine the pure tone audiometry of patients with anaemia and investigate the potential correlation between anaemia and hearing loss. In addition, anaemia possesses geographical variations with dimorphic anaemia being common in India. We aimed to find the association between dimorphic anaemia and hearing loss which is a novel finding of our study.
Materials and Methodology
The research was conducted at the Department of Otorhinolaryngology and Department of General Medicine of a tertiary care hospital from Feb 2023 to July 2023 following approval from the Institutional Human Ethical Committee. The required sample size was calculated as 100 based on the prevalence of anaemia in India, 49.8% (NFHS-5), 80% power and 10% allowable error with formula (z2pq)/l2.
Inclusion Criteria
Newly diagnosed cases of anaemia (Men with haemoglobin levels less than 13 g/dl and women with haemoglobin levels less than 12 g/dl) [7].
Patients between the ages of 18 years to 60 years belonging to both sexes.
Exclusion Criteria
Patients who are not clinically stable.
Patients with a previous history of surgeries in the ear.
Patients with pre-existing hearing loss in one or both ears.
Patients with migraine.
Pregnant women.
Procedure
Written informed consent was obtained from the study participants by explaining the need for the research study. Detailed history and a comprehensive medical examination were conducted, which involved the assessment of pallor, clubbing, and cyanosis. Evaluation of the ear, nose, and throat was done. A series of tuning fork tests, including Rinne’s test, Weber’s test, and absolute bone conduction test, were conducted. Haemoglobin levels were measured and anaemia was classified as: Mild (Haemoglobin 11.0 to 12.9 g/dL in males and 11 to 11.9 g/dL in females), Moderate (Hb: 8.0 to 10.9 g/dL) and Severe (Hb < 8 g/dL) according to WHO classification of anaemia (2011). Peripheral smear was done to identify the type of anaemia. Pure tone audiometry using a well calibrated audiometer with circumaural headphones, was conducted on patients diagnosed with anaemia, and the findings were documented. Conductive hearing loss was defined as normal bone-conduction thresholds, but air-conduction thresholds poorer than normal by at least 10 dB and thereby producing an air-bone gap in pure tone audiometry. Sensorineural hearing loss was defined as both bone- and air-conduction thresholds higher than 25 dbHL but within 10 dB of each other (thereby no air-bone gap). The Statistical package SPSS version 21 was used to perform statistical tests. Qualitative data were expressed in frequencies and quantitative data were expressed in terms of mean and standard deviation. Association between the severity of anaemia and hearing loss was evaluated by Chi-square analysis to determine the statistical significance.
Results
The mean age of the study participants is 36.5 ± 11.75 years. 94% of the study participants were females and the majority were literate (69%) and employed (58%). Nearly 60% of them had symptoms of anaemia like tiredness and fatigue whereas only 12% of them reported having tingling and numbness in the extremities. Most of them (96%) had pallor, while clubbing was found to be present in only 3% of them on examination (Table 1). None of the patients had cyanosis. Anaemia was classified according to haemoglobin levels and peripheral smear (Table 2).
Table 1.
General characteristics and clinical findings of the study population, N = 100
| Characteristics | N/% |
|---|---|
| Mean age (SD*) | 36.5 ± 11.75 years |
| Age | |
| ≥ 35 years | 57 |
| < 35 years | 43 |
| Gender | |
| Male | 6 |
| Female | 94 |
| Education | |
| Literate | 69 |
| Illiterate | 31 |
| Occupation | |
| Employed | 58 |
| Unemployed | 42 |
| Tiredness and fatigue | |
| Present | 60 |
| Absent | 40 |
| Tingling and numbness of extremities | |
| Present | 12 |
| Absent | 88 |
| Pallor | |
| Present | 96 |
| Absent | 4 |
| Clubbing | |
| Present | 3 |
| Absent | 97 |
*SD = Standard Deviation
Table 2.
Classification of anaemia in study population, N = 100
| Characteristics | N/% |
|---|---|
| Classification based on haemoglobin levels | |
| Mild anaemia | 9 |
| Moderate anaemia | 64 |
| Severe anaemia | 27 |
| Peripheral smear | |
| Microcytic hypochromic RBCs** | 93 |
| Macrocytic hypochromic RBCs** | 7 |
Classification of anaemia based on WHO classification, **RBCs = Red Blood Cells
Pure Tone Audiometry revealed SNHL in 48% of the study population. The mean haemoglobin concentration is 8.76 ± 0.849 g/dl. All the study participants had ferritin levels less than 24 ng/dl which infers the prevalence of Iron deficiency anaemia in all the study participants. Moreover of the 100 participants, 7 of them had megaloblastic anaemia. The association between age and SNHL was found to be statistically significant with a Chi-square value of 3.949 and P value of 0.047 (< 0.05) whereas the association between gender and SNHL was found to be statistically in significant by Fischer’s exact test and the association between education and occupation was found to be statistically insignificant by Chi-square test (Table 3). Of the 100 participants, 46.8% of moderately anaemic patients and 64.3% patients with severe anaemia exhibited sensorineural hearing loss The association between severity of anaemia and SNHL was found to be statistically significant with a P value of 0.012 (< 0.05) by Fischer’s exact test. But there was no statistical association between peripheral smear and hearing loss by Chi-square test (Table 4). Hence, null hypothesis is proved for the association between dimorphic anaemia and hearing loss in our study. Threshold intensity at various air conduction and bone conduction frequencies among different groups was compared (Table 5).
Table 3.
Association between demographic characteristics and hearing loss by Chi-square test, N = 100
| Characteristics | Sensorineural Hearing Loss | Chi-square value | P value | |
|---|---|---|---|---|
| Present | Absent | |||
| Age | ||||
| < 35 years | 20 | 32 | 3.949 | 0.047 |
| ≥ 35 years | 28 | 20 | ||
| Gender | ||||
| Male | 4 | 2 | 0.891 | 0.345 |
| Female | 44 | 50 | ||
| Education | ||||
| Literate | 36 | 33 | 1.554 | 0.213 |
| Illiterate | 12 | 19 | ||
| Occupation | ||||
| Employed | 30 | 28 | 0.767 | 0.381 |
| Unemployed | 18 | 24 | ||
Table 4.
Association between type and severity of anaemia and Sensorineural hearing Loss by Fischer’s Exact Test, N = 100
| Classification of anaemia | Sensorineural Hearing Loss | Fischer’s exact value | P value | |
|---|---|---|---|---|
| Present | Absent | |||
| Type of anaemia | ||||
| Microcytic hypochromic anaemia | 46 | 47 | 1.138 | 0.286 |
| Dimorphic anaemia *** | 2 | 5 | ||
| Severity of anaemia | ||||
| Mild anaemia | 1 | 9 | 8.798 | 0.012 |
| Moderate anaemia | 29 | 33 | ||
| Severe anaemia | 18 | 10 | ||
***Dimorphic anaemia = peripheral smear shows hypochromic and orthochromic red blood cells
Table 5.
Threshold intensity at various air conduction and bone conduction frequencies (decibels), N = 100
| Pure tone audiometry frequencies | Mild anaemia | Moderate anaemia | Severe anaemia | |
|---|---|---|---|---|
| Right ear | 500 Hz | 18.89 ± 17.1 | 24.92 ± 18.91 | 19.63 ± 19.21 |
| 1000 Hz | 26.67 ± 19.04 | 31.48 ± 20.66 | 26.48 ± 19.6 | |
| 2000 Hz | 32.22 ± 19.54 | 36.95 ± 21.87 | 32.96 ± 22.63 | |
| Pure tone AC threshold of right ear | 24.2 ± 18.05 | 31.05 ± 20.48 | 26.36 ± 20.04 | |
| Pure tone BC threshold of left ear | 29.6 ± 21.15 | 32.26 ± 20.82 | 28.25 ± 19.66 | |
| Left ear | 500 Hz | 29.44 ± 18.61 | 21.56 ± 18.36 | 21.30 ± 17.46 |
| 1000 Hz | 36.11 ± 20.27. | 26.95 ± 20.99 | 27.41 ± 19.33 | |
| 2000 Hz | 44.44 ± 21.28 | 35.23 ± 22.15 | 34.26 ± 21.61 | |
| Pure tone AC threshold of left ear | 34.1 ± 20.15 | 28.02 ± 20.44 | 26.96 ± 18.92 | |
| Pure tone BC threshold of left ear | 36.3 ± 19.9 | 31.03 ± 20.85 | 28.25 ± 19.02 | |
Discussion
Anaemia, a pathological condition, is characterized by an inadequate capacity to transport oxygen, thereby failing to meet the body’s physiological requirements. This condition is closely associated with alterations in the quantity of red blood cells, which can either be elevated or diminished. Iron deficiency and Vitamin B12 deficiency are the two main nutrient deficiency causes of anaemia, causing iron deficiency and megaloblastic anaemia, respectively, and if both are deficient, the condition is known as dimorphic anaemia. Iron deficiency anaemia is the most prevalent micronutrient condition in the world, compromising the health and socioeconomic status of tens of thousands of men, women, and children. The prevalence of Iron deficiency anaemia varies in different states across India due to different factors ranging from poor economic, educational status, rural residence, and exposure to mass media among women. [8].
The susceptibility of the cochlea to ischemic damage is attributed to the exclusive supply of blood to this area by the labyrinthine artery. [9] Chang Y-L et al. and Dubyk MD et al. in their study found that Iron deficiency anaemia was a potential risk factor for ischemic stroke owing to reduced haemoglobin levels that result in impaired oxygen-carrying capacity. [10, 11] Chung S-D et al. observed a higher risk of sudden sensorineural hearing loss (SNHL) in individuals with vascular disease. [12] A plausible vascular pathway that connects hearing loss with iron deficiency anaemia (IDA) is the heightened susceptibility of patients with reactive thrombocytosis to IDA. [13, 14] The regulation of thrombopoiesis is influenced by iron, and prior research has established links between thrombocytosis and blood loss. [15, 16] Iron deficiency has been found to cause degradation of lipid saturase and desaturase, leading to impaired energy production and subsequent myelin production, as reported in a recent medical journal article. [17] The impairment of conduction velocity caused by damage to the myelin surrounding the auditory nerve may lead to noise-induced hearing loss. [18] Brown AM et al. attributed this to alterations in the density of sodium channels. [19].
According to Schieffer KM et al., anaemia and hearing loss are significant factors that contribute to health impairment on a global scale. [20] Hearing loss is a commonly overlooked health issue that receives limited public health attention, in contrast to anaemia. Limited research has been conducted on the correlation between IDA and hearing loss. Assuming that Iron Deficiency anaemia (IDA) could be a potential risk factor for hearing impairment, it is postulated that the prevalence of hearing loss may have been underestimated in the existing literature. Additional research from developing nations would enhance comprehension of the correlation between the two conditions.
Iron Deficiency anaemia (IDA) continues to be a significant public health issue worldwide, with its correlation to hearing loss being a cause for greater concern. The prevention, early diagnosis, and treatment of IDA have the potential to provide dual benefits by reducing the burden of anaemia and potentially mitigating hearing loss. Prior studies have emphasized the significance of conducting screenings. [21–23].
In this study, a significant correlation was found between anaemia and sensorineural hearing loss, especially in those patients with moderate and severe sensorineural hearing loss. While prior studies have explored the connection between anaemia and hearing impairment, limited research has delved into the potential implications of dimorphic anaemia, a specific subtype, which has received less attention in the context of auditory function. This was specifically investigated in this study. Despite the unique focus on dimorphic anaemia, the study’s results revealed that there was no significant association between dimorphic anaemia and hearing impairment. This finding suggests that while anaemia, in general, may have an impact on auditory function, the specific subtype of dimorphic anaemia does not seem to be a significant contributing factor. It’s important to note that the absence of a significant association does not rule out other potential contributing factors to hearing impairment in patients with dimorphic anaemia. Further research may be needed to identify other variables or comorbid conditions that could impact auditory function in these individuals.
Thus, the importance of screening for hearing loss in individuals with anaemia may be heightened in areas with a high prevalence of anaemia. Further studies are needed to explore strategies for integrating hearing loss screening for anemic cases, or vice versa, into existing public health and clinical practices. The rationale for exclusively employing pure tone audiometry in this study was based on the lack of objective tests available to quantify hearing impairment. Consequently, the Pure-Tone Audiometry (PTA) proved to be a suitable tool for examining the correlation between the extent of hearing loss and the presence of anaemia.
Conclusion
In summary, the current investigation delving into the association between anaemia patients and hearing loss has unveiled a statistically noteworthy connection between moderate to severe anaemia and sensorineural hearing impairment. The aforementioned discovery emphasizes the potential influence of the severity of anaemia on auditory capabilities and emphasizes the necessity for heightened attentiveness in assessing the state of hearing in individuals with moderate to severe anaemia. Intriguingly, our study revealed no statistically significant association between dimorphic anaemia and auditory impairment. Nevertheless, it is imperative to acknowledge that additional investigation is necessary to delve more profoundly into the underlying mechanisms implicated.
In light of the ramifications of auditory impairment on individuals diagnosed with anaemia, the findings of this investigation emphasize the significance of integrating auditory screening initiatives within medical facilities that serve a population with a notably elevated prevalence of anaemia. The timely detection and intervention of auditory dysfunction in individuals with anaemia may yield advantageous outcomes in mitigating subsequent impairment. Potential avenues for investigation involve the incorporation of regular auditory evaluations within the established treatment regimens for individuals afflicted with anaemia, thereby facilitating expeditious identification and suitable intervention for instances of auditory impairment. The integration of expertise from hematologists, audiologists, and healthcare policymakers holds promise in the advancement of holistic screening strategies, thereby enhancing the overall healthcare outcomes for this susceptible demographic.
Declarations
Informed Consent
As per university standards written ethical approval has been collected and preserved by the author(s).
Ethical Approval
As per university standards written ethical approval has been collected and preserved by the author(s).
Competing Interests
The authors have declared that no competing interests exist.
Footnotes
Publisher’s Note
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