This was a hospital-based cross-sectional study conducted over 8 months from October 2024 to May 2025.

The study was conducted at the paediatric sickle cell clinic of the Kilimanjaro Christian Medical Centre (KCMC), which is a zonal referral hospital. Kilimanjaro Christian Medical Centre is situated in the Northern Zone of Tanzania with a bed capacity of over 800, serving approximately 13 million people and 400 patients with SCD. It also serves as a teaching hospital for the KCMC University.

All available paediatric patients with SCD eligible for the study were enrolled.

A consecutive sampling technique was used, whereby all patients who met the inclusion criteria during the study period were recruited.

Patients with SCD, confirmed by Hb electrophoresis, aged 4 years to 17 years old, whose caretakers consented.

Patients with SCD with altered mental status, congenital anomalies of the external ear, such as canal atresia (limits audiology assessment), and patients with a history of ear surgery.

Independent variables were age, sex, frequency of painful vaso-occlusive crises (documented crises requiring hospital visit or admission), number of blood transfusions, use of medications (ototoxic drugs, hydroxyurea), number of admissions, presence of other SCD complications (stroke, anaemia, acute chest syndrome and asplenia), presence of comorbidities (diabetes mellitus and hypertension), family history of hearing loss, age of initiation of treatment and recurrent upper respiratory tract infections. The dependent variable was hearing loss.

The primary outcome was hearing loss, assessed using pure-tone audiometry and defined as a pure-tone average greater than 20 dB across frequencies of 0.25 kHz to 8 kHz in accordance with the updated World Health Organization criteria. The pattern of hearing loss was characterised in terms of type, severity and laterality; type was classified as conductive hearing loss (CHL), sensorineural hearing loss (SNHL) or mixed hearing loss (MHL), severity was categorised as mild (20 dB – 34 dB), moderate (35 dB – 49 dB), moderate severe (50 dB – 64 dB), severe (65 dB – 79 dB), profound (80 dB – 94 dB) and deafness (≥ 95 dB), and laterality was defined as unilateral or bilateral involvement. Variables assessed as associated factors include demographic and clinical characteristics such as age, sex, duration of disease and other relevant patient-related factors.

A structured electronic data collection sheet was developed and administered using Kobo Toolbox to record patients’ demographic information, clinical characteristics, otological examination findings and audiogram results.

All sickle cell patients attending the sickle cell clinic at KCMC were evaluated before the audiometric test. Patients who met the inclusion criteria were asked for assent. Demographic data were collected, and an otoscopic examination was performed using an otomicroscope to examine the ear canal and tympanic membrane at otorhinolaryngology clinic. Impacted cerumen and foreign bodies were removed before the audiometric test.

Pure-tone audiometry was performed in a sound-treated room that met background noise levels according to the International Organisation for Standardisation (ISO) 8253-1 standards by an audiologist using a pure-tone audiometer, a calibrated diagnostic audiometer (with both air and bone conduction transducers) that complied with ISO 389 standards to ensure accuracy. During a pure-tone audiometric test, patients respond to auditory stimuli delivered via air conduction (through headphones) and bone conduction (vibrating the skull directly). The typical frequency range tested is 0.25 kHz to 8 kHz, which covers critical speech frequencies. Testing was carried out using the modified Hughson-Westlake method in which tone intensity was decreased by 5 dB until the hearing threshold level was determined. Both air and bone conduction thresholds were recorded, and results were plotted on a standard audiogram to classify the type, degree (severity), laterality and frequencies affected. High-frequency hearing thresholds (HFHTs) were defined as the average hearing threshold at 4, 5, 6 and 8 kHz. Low-frequency hearing thresholds (LFHTs) were defined as the average hearing threshold at 0.25, 0.5, 1, 2 and 3 kHz in both ears.

Data were entered and analysed using Statistical Package for the Social Sciences (SPSS) version 20. The mean and standard deviation (s.d.) were calculated for continuous variables, whereas proportion and frequency were used to summarise categorical variables. Cross-tabulations with Chi-square tests were used to explore associations between variables. Univariable logistic regression was first used to assess the crude association between independent variables and hearing loss; variables with a p-value of less than 0.05 were included in multivariable logistic regression to identify independent factors. The strength of association was expressed using adjusted odds ratios (AORs) with 95% confidence intervals (CI), and a p-value of less than 0.05 was considered statistically significant.

Ethical clearance to conduct this study was obtained from the KCMC University College Research Ethics Committee (No. PG 156/2024).

A total of 90 patients with SCD were included in the final analysis (Table 1). The age ranged from 4 years to 17 years old, with a mean age of 10.67 ± 4.22 years. The male to female ratio was 60:40. In all, 70% (n = 63) patients resided in urban areas, with more than half were attending primary school (56.7%, n = 51 patients).

In all, 31% (28) of patients had hearing loss (Figure 1); 86% of patients were diagnosed with SCD at or before the age of 5 years, with a mean age at diagnosis of 3.15 ± 2.16 years. A total of 91% had a normal body mass index (BMI) of 20.41 ± 1.66 kg/m². Of the 90 patients, 93.3% were on hydroxyurea and folic acid treatments, while 6.7% used folic acid alone. Approximately 26.7% of the study patients had experienced SCD-related complications, while 27% had a history of blood transfusion. Additionally, only 2.2% reported prior exposure to ototoxic drugs (Table 2).

In this study, 28/90 patients were found to have hearing loss. Among affected patients, 57% (16) had bilateral hearing loss, and 43% (12) had unilateral hearing loss. With regard to severity, moderate hearing loss was the most common presentation, affecting 35.7% (10/28) of patients, followed by mild hearing loss in 32.1% (9/28), moderate-to-severe hearing loss in 25.0% (7/28) and severe hearing loss in 7.1% (2/28). Sensorineural hearing loss was the most common type of hearing loss, accounting for 53.6% (15/28) of cases, followed by CHL in 35.7% (10/28) and MHL in 10.7% (3/28) (Figure 2).

Among patients with SNHL, high-frequency hearing loss was the predominant pattern, occurring in 58.8% (10/17) of patients, while 29.4% (5/17) had low-frequency hearing loss and 11.8% (2/17) had hearing loss affecting all frequencies (Figure 3).

In assessing factors associated with hearing loss among paediatric patients with SCD, only the presence of painful vaso-occlusive crises within the past year was found to be significantly associated with hearing loss in both univariate and multivariate analyses (Table 3). In the univariate analysis, patients who had experienced painful vaso-occlusive crises within the past year had approximately 15 times higher odds of developing hearing loss compared to those without such episodes (Crude odds ratio [COR]= 15.88; 95% CI: 4.8–12.55; p < 0.001). In the multivariate analysis, the association remained significant, with affected patients showing six times higher odds of hearing loss compared to those without painful crises (Adjusted odds ratio (AOR) = 6.3; 95% CI: 1.61–9.69; p < 0.008).

This study focused on a vulnerable population of children with SCD, who are predisposed to multiple systemic complications, including hearing impairment. By examining this group, the study draws attention to an often overlooked yet clinically significant problem. Furthermore, conducting the research in a low-resource setting where audiological services are limited provides valuable insights that may inform the development of targeted interventions for individuals with SCD.

This study has several limitations. Firstly, the relatively small sample size and single-centre design limit the generalisability of the findings to other regions and populations. Secondly, the use of a hospital-based sample may introduce selection bias, as children attending the clinic may differ from those in the wider community with SCD, which may further affect representativeness. Thirdly, the absence of a control group restricts direct comparison with children without SCD, limiting broader interpretation of the findings. Although multivariable analysis was performed to adjust for potential confounders, residual confounding from unmeasured variables cannot be excluded. In addition, the study did not account for some potential confounding factors, including genetic predispositions, which may also influence the development of hearing loss.

This study recommends integrating targeted hearing screening into SCD management at both national and institutional levels. Routine hearing assessments should be prioritised for all patients, and in particular for patients with recurrent vaso-occlusive crisis. Prevention of SCD crisis by optimising use of hydroxyurea and rapid intervention to manage vaso-occlusive events would further prevent associated sensorineural damage. Conductive hearing loss associated with OM, especially in the context of an impaired immune system in SCD, requires more aggressive identification and treatment. Further multicentre and longitudinal studies are needed to enhance generalisability and clarify causal relationships between SCD and hearing loss. Future research should employ objective audiological assessments and include broader age groups.