1 Introduction
Hearing loss is characterized by a reduced ability or complete inability to perceive sound, typically with a hearing threshold above 20 dB [
1]. Hearing loss can be conductive, sensorineural, or mixed. Conductive hearing loss occurs when sound waves cannot reach the inner ear. Sensorineural hearing loss (SNHL) results from issues affecting the cochlea, auditory nerve, or central nervous system. Mixed hearing loss arises from a combination of factors causing both sensorineural and conductive hearing loss [
2]. Hypertension can contribute to SNHL through various proposed mechanisms. One hypothesis suggests that inner ear damage, caused by increased vascular viscosity, leads to hypoperfusion of the cochlea, ultimately resulting in SNHL [
3,
4]. The other proposed mechanism is excessive reactive oxygen species (ROS) production due to ischemia which overwhelms antioxidants defenses in the cochlear causing damage of hair cells and eventually cell death leading to SNHL [
5]. Hypertension causes reduced endothelial repair capacity in the cochlear vascular bed by lowering circulating level of endothelial progenitor cells which later contributes to cochlear vascular damage resulting into SNHL [
6]. The global prevalence of hypertension is estimated at 1.39 billion. In Sub-Saharan Africa, studies have shown a hypertension prevalence of 16.2%, which is expected to rise to 68% by 2025 [
1,
7]. According to the Tanzanian strategic and action plan for control and prevention of non-communicable diseases, the burden of cardiovascular diseases including hypertension is 12% [
8], while in northern Tanzania, a study found that 28.0% of adults were affected by hypertension [
9]. Globally, an estimated 1.5 billion people are affected by hearing loss, with Africa accounting for approximately 9% of this prevalence. By 2050, the number of individuals with hearing loss is projected to increase to 2.5 billion [
8].
Research data on hearing loss among hypertensive patients and associated factors are scarce around East Africa, including northern Tanzania. One study conducted at a cardiac institute in Tanzania showed the SNHL was prevalent in about 75.4% of hypertensive patients [
10]. Though this study does not explore on factors associated with SNHL. Our current study will add more knowledge to the researchers and community on the prevalence, patterns, and factors associated with SNHL among hypertensive adults at a tertiary hospital in the region.
2 Material and Methods
2.1 Participants and Study Procedure
This cross-sectional hospital-based study was conducted at Kilimanjaro Christian Medical Center (KCMC), a tertiary academic hospital in northern Tanzania. The study involved 201 consented hypertensive adults aged 18–60 years who met the inclusion criteria and it was carried from October 2023 to May 2024. Verbal consent was obtained from those who were unable to read and write and written consent was obtained from those who were able to read and write. Sample size was calculated by using Cochrane formula adopted from the study done in Nigeria [
11]. A systematic random sampling method was employed, the patients were required to count number from 1 up to 5 and every fifth eligible patient was picked to be involved in the study including those who came for follow-up and were normotensive taking into account that they have already enrolled as hypertensive patients. Inclusion criteria encompassed all consenting hypertensive adults aged 18–60 years, while exclusion criteria included individuals with diabetes mellitus, renal disease, HIV/AIDS and history of stroke or head injury, active ear infections, or audiometric features of noise-induced hearing loss. After being excluded, patients with these conditions were sent to their respective clinics for further evaluation and management.
Data collection was conducted using a structured tool that included socio demographic characteristics (age, gender), duration of hypertension, history of smoking, history of drinking alcohol, history of ototoxic drugs use (frusemide and/or hydrochlorothiazide), otoscopic findings and pure-tone audiometry (PTA) results. The associated factors (e.g., age, gender, duration of hypertension, smoking, alcohol use and ototoxic drug use) were all confirmed and verified through patient medical records reviews, structured interviews and by statistical analysis through multivariate regression. Prolonged hypertension was operationally defined as a documented diagnosis of hypertension ≥ 5 years regardless of intermittent control. The interviews were conducted in a language understood by the participants, questions were simplified and explained when necessary and verification on associated factors made thoroughly in files in order to minimize recall and literacy bias. The patients with earwax and foreign bodies were removed, and complex cases were referred to the ENT clinic. Patients with discharging ears were also referred for further management. Pure tone audiometry was performed in a soundproof room (with ambient noise of less than 30 dB) by a qualified audiologist using a Clinical Audiometer (AC40 2003, made in Denmark) with standard headphones. Hearing thresholds were measured at frequencies of 250, 500, 1000, 2000, 4000, and 8000 Hz. Patients with conductive or mixed hearing loss were excluded from the SNHL category. SNHL was classified according to the modified 2021 WHO guidelines as follows mild (20–35 dB), moderate (35–50 dB), moderately severe (50–65 dB), severe (65–80 dB), profound (80–95 dB) and complete hearing loss ≥ 95 dB. Independent variables included age, sex, duration of hypertension, smoking, alcohol consumption, and ototoxic drug use, while the dependent variable was SNHL.
2.2 Statistical Analysis
Data were analyzed using SPSS (version 26), incorporating univariate analysis and multivariate logistic regression. Mean and standard deviation were calculated for continuous variables, while proportions and frequency tables summarized categorical variables. Logistic regression identified factors associated with hearing loss, with odds ratios (ORs) used to measure the significance of associations between independent and outcome variables. A p value of ≤ 0.05 was considered statistically significant.
3 Results
This study included 201 hypertensive adults, with a mean age of 46.8 years; 75.6% were aged ≤ 50 years, and 24.4% were > 50 years. Females constituted 55.7% of participants. Hypertension duration was < 5 years in 66.7% of cases and > 5 years in 33.3%, with a median duration of 3 years. Alcohol consumption was reported by 30.8%, cigarette smoking by 12.9%, and ototoxic drug use by 19.9% of participants (Table 1). The prevalence of SNHL was 23.9% with higher rates among participants aged > 50 years (59.2%) compared to ≤ 50 years (12.5%, p < 0.01). Females were more affected (31.3%) than males (14.6%, p = 0.01). SNHL was more prevalent in participants with hypertension for > 5 years (64.2%) than those with < 5 years (3.7%, p < 0.01). In Table 1, the Shapiro–Wilk test was used to evaluate the distribution of continuous variables. Age was normally distributed (p = 0.21) whereas duration of hypertension was not (p = 0.001). Age is therefore presented as mean ± SD and duration of hypertension as median (IQR).
Alcohol consumption and cigarette smoking were associated with higher SNHL prevalence (56.5% and 53.8%, respectively) compared to non-drinkers (9.4%) and non-smokers (19.4%, p < 0.01). Ototoxic drug use also showed a higher prevalence (65.0%) compared to non-users (13.7%, p < 0.01) (Table 2). Most cases of SNHL were bilateral (81.3%), with 10.4% right-sided and 8.3% left-sided (Figure 1). Mild SNHL was most common (70.8%), followed by moderate (18.8%) and moderately severe (10.4%) forms (Figure 2). Significant factors associated with SNHL included cigarette smoking (OR = 21.2, p < 0.01), hypertension duration > 5 years (OR = 16.0, p < 0.01), female gender (OR = 9.4, p = 0.01), age > 50 years (OR = 6.4, p < 0.01), alcohol consumption (OR = 5.5, p < 0.01), and ototoxic drug use (OR = 4.5, p = 0.02) (Table 3).
4 Discussion
In the current study, SNHL was prevalent among hypertensive patients. This finding tallies with a study done in Dar es Salaam, Tanzania where SNHL was found to be prevalent [
10], though in our study, the prevalence was lower than that of Dar es Salaam and in other countries [
12,
13]. This discrepancy may be attributed to differences in sample size and statistical power. Bilateral and mild SNHL were the predominant patterns. These findings align with other studies done in Dar es Salaam, Tanzania, as well as in Brazil and South Africa [
10,
14,
15], that can be explained by similarities in study designs used in these studies.
In our study, cigarette smoking was found to be a major significant factor associated with SNHL. The sample size of smoking subgroup is small (
n = 26) which may result in overestimation of odds ratios value. This is similar to the study which was done in Turkey and Nigeria [
16,
17], these similarities are explained by both studies used a hospital based settings. The population survey study done in Australia confirms associations between smoking and prevalent hearing loss [
18]. This similarity is explained by both studies using adult population. Also these findings highlight the importance of smoking cessation for hypertension patients. The duration of hypertension of equal or more than 5 years was found to carry a risk of SNHL, and these findings tally with studies done in Tanzania (Dar es Salaam) and India [
10,
12,
13,
19] and can be explained by similarities in study settings and study designs. These findings emphasize the need for early detection and effective management of SNHL among hypertensive patients. Our study identified female gender to have a higher risk of SNHL. This finding is similar to the study done in India [
12], which may be explained by the predominance of females in both studies.
The study done in Brazil shows that male gender was an independent risk factor for SNHL. Contrary to our study, this might be explained by differences in study approaches: our study used a cross-sectional design, while the study in Brazil used a case-control design [
14].
Advanced age of more than 50 years was found to be associated with SNHL. This is similar to the studies done in Tanzania (Dar es Salaam) and India [
10,
12,
13], which may be explained by the fact that hypertensive patients tend to have accelerated hearing loss, apart from normal presbycusis which occur in advanced age, and is supported by a longitudinal study done to assess the effects of age and gender on speech reception scores. In this study, speech reception scores worsened with increasing age [
18].
The use of ototoxic drugs, especially loop diuretics like frusemide and hydrochlorothiazide, was another notable risk factor for SNHL, consistent with existing research on the cellular degeneration caused by these medications in the inner ear [
13,
17,
19]. These findings underscore the importance of addressing modifiable risk factors, such as smoking and alcohol consumption, and exercising caution when prescribing ototoxic drugs to hypertensive patients.
In light of Tanzania's non-communicable diseases (NCD) policy, the results from this study will strengthen the policy by providing a real time evidence that supports integrated, preventive and holistic management of hypertension. It will also be an eye opener on not just addressing cardiovascular complications of hypertension but also sensory complications specifically SNHL through risk reduction and early intervention.
5 Conclusion
This study highlights a significant burden of SNHL among hypertensive patients, with bilateral and mild forms being the most prevalent. Key risk factors identified include cigarette smoking, prolonged hypertension, female gender, older age, alcohol consumption, and the use of ototoxic drugs. The findings emphasize the importance of early detection and targeted interventions to address modifiable risk factors, particularly smoking, prolonged hypertension, and the use of ototoxic medications. By mitigating these risks, the impact of SNHL on hypertensive patients can be reduced, ultimately improving their quality of life. Further research is warranted to explore causal relationships and effective prevention strategies in this population.
5.1 Recommendations
Hypertensive patients should undergo routine audiometric screening for early detection and management of SNHL to enhance their quality of life. Health education programs should emphasize avoiding modifiable risk factors, including smoking and alcohol consumption. Further community-based studies are needed to better understand the prevalence and association of SNHL with hypertension in the general population.
5.2 Limitations of the Study
This study is a hospital-based nature limits generalizability to the broader population. Additionally, some associated factors to SNHL, such asdyslipidemia, poorly controlled hypertension, hypothyroidism, environmental exposures and passive smokers may have been overlooked. Not all prescriptions could be retrieved that may include over-the-counter ototoxic drugs. Furthermore, the cross-sectional design precludes establishing causality between hypertension and SNHL.
2026 The Author(s). Eye & ENT Research published by John Wiley & Sons Australia, Ltd on behalf of Higher Education Press.
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