This is the first study to examine the association between social determinants of health and hearing loss in children in South Africa, and findings from this study contribute to the growing body of evidence globally that examine these associations. We found that females were more likely to have hearing loss than male children. Similarly, younger children were more likely to have hearing loss than older children. Exposure to cigarette smoking, type of housing (mud house), ablution facilities (use of pit latrine), and no availability of clean drinking water were all associated with higher odds of hearing loss.
The factors associated with hearing loss in our study align with some of the emerging evidence globally. However, it is worth noting that previous studies have shown variability in the association between sex and hearing loss, while some studies have found lower odds of hearing loss in females than in males,56,57 other studies found lower odds of hearing loss in males than in females.58 For instance, a 2017 UK study56 with 3292 adults showed increased odds of hearing loss among male participants (OR: 1.7, 95% CI: 1.4–2.0) when compared to female participants. Similarly, Tsimpida et al57 also showed increased odds of hearing loss among male participants in a 2019 UK study. In contrast, a recent cross-sectional study58 among 810 South African participants found increased odds of hearing loss (OR: 2.0; 95% CI: 1.7–3.3) amongst female participants when compared to male participants.
The contextual factor with the highest odds of hearing loss in this study was the use of pit latrines for ablution, even after accounting for age, sex, and exposure to cigarette smoking in the household. While a clear link between the proper disposal of excreta and improved health has been established,59 there is limited research examining the association between the use of pit latrines and hearing loss. Nevertheless, two recent studies in KwaZulu-Natal, South Africa, identified high concentrations of Staphylococcus aureus60 and Escherichia coli (E. coli)61 on the surface areas of pit latrines such as doorknobs. E. coli and Staphylococcus aureus are common pathogens that cause otitis media in children, as these pathogens are often introduced into the ear canal and subsequently the middle ear cavity through contact with contaminated surfaces, which leads to the development of otitis media.62 The latter is often accompanied by conductive hearing loss. It is possible that using pit latrines could lead to otitis media due to E. coli and Staphylococcus aureus infection, common pathogens found in such facilities and associated with hearing loss.
On the other hand, Tiwari et al63 argue that the decision regarding the choice of ablution facilities is complex and can be affected by other factors, such as socioeconomic status and the availability of piped water for flushing. This suggests a connection between the use of pit latrines, the availability of piped water and socioeconomic status. In this study, children without access to piped or clean drinking water were twice as likely to have hearing loss than those with access to clean or piped drinking water, and this association remained significant after adjusting for smoking exposure, participant age and sex. As a result, it is difficult to determine if the higher odds of hearing loss in children using pit latrines in this study was due to conductive hearing loss due to otitis media, a lower socioeconomic status or unavailability of water in the household or a combination of all these factors.
We found over three times the odds of hearing loss in children exposed to smoking in the households when compared to children who were not exposed to smoking, which has been demonstrated in previous studies.28–31 While the exact pathophysiology remains unclear, there is an increased risk of otitis media in children exposed to smoking through the suppression of the immune system, enhancement of bacterial adherence factors, the consequence of exposure to toxins within tobacco smoke, and impairment of the respiratory muco-ciliary apparatus leading to Eustachian tube dysfunction and the resulting otitis media.33,34 More than 60% of those exposed to smoking in the xxx study also had otitis media, linking smoking exposure to otitis media and conductive hearing loss.28,35 In other studies, smoking exposure has led to sensorineural hearing loss, which is associated with dysfunction of the endothelial physiology of the basilar membrane in the cochlea, microvascular impairment and apoptosis of cochlear hair cells.29,36 The inner ear is an energy-consuming organ that relies on sufficient blood supply, making it vulnerable to changes in blood flow that can lead to sensorineural hearing loss.37
Our findings also showed higher odds of hearing loss in children whose parents had lower income levels or those with lower educational attainment, which is similar to previously reported studies.56,64–66 For instance, a study in England with 3 292 adults showed that those in the lowest income tertile were almost twice as likely to have hearing loss when compared to those in the highest income tertile.56 While research has indicated a connection between lower socioeconomic status and hearing loss, it is important to recognise that people who develop hearing loss in childhood are less likely to complete their education, potentially leading to difficulties in obtaining higher-paying jobs due to reduced educational attainment.67 Specific to educational attainment, a 2017 Brazilian study showed that adults without education were twice as likely to have hearing loss when compared to those with higher education.68 Similarly, in England, adults with no formal education had twice the odds of hearing loss when compared to those with graduate-level qualifications.57 In China, a 2018 population-based survey with 25 860 adults showed that those with some primary-level education had twice the odds of hearing loss when compared to those with a high school-level education.69 In Japan, a case‒control study with 1 039 participants found that those with low education attainment were three times more likely to have hearing loss than those with higher education.70
We did not find an association between living in rural areas and increased odds of having hearing loss, which is in contrast to other findings.71–73 The increased odds could be because hearing loss is positively correlated with other indicators for a lower socioeconomic status, such as poverty, reduced educational achievement, and manual labour occupations, which are characteristics more prevalent in rural settings.71
Our study has strengths and limitations to consider. The careful calculation of sample size, with high statistical power and representativeness of the target population, minimises random error and selection bias. The comprehensive dataset without missing data ensures the accuracy of the analysis. The data collected by an experienced audiologist and double-checked data entries contributed to the study’s reliability. Furthermore, the inclusion of participants from diverse socioeconomic areas and locations within Mthatha enhances the potential generalisability of the findings to other areas with similar demographics. However, limitations include the cross-sectional design, which hinders the establishment of causal relationships between variables. Some information reported on socioeconomic status may not be accurate, as participants may have given false information for social desirability. Furthermore, unmeasured variables and the absence of classification of hearing loss types and severity limit the study’s ability to explore the impact of specific factors on hearing loss types.
Our study findings have implications for public health policy and practice. For example, policymakers, public health authorities and multi-ministry collaboration are needed to increase awareness, re-evaluate and ensure enforcement of Tobacco Control guidelines. Additionally, these collaborative efforts could focus on the development and implementation of policies that improve access to clean drinking water and improve sanitation and hygiene practices for those who use pit latrines to ensure that children are better protected against such exposure. Furthermore, there is a need to broaden participation and enhance educational attainment, which could be attained through Adult Based Education, Technical and Vocational Education and Training, and improved access to educational funding for those who want to further their education through bursaries and the National Student Financial Aid.
The findings of our study can also inform future research. Examination of the pathophysiology of hearing loss in children exposed to cigarette smoking and those using pit latrines is recommended, given that 38% (n = 199) of children in this study were exposed to cigarette smoking, while over 80% (n = 417) used pit latrines. Furthermore, given that this study was conducted in one area of the Eastern Cape province of South Africa and that data collection on different populations from other parts of the province and the country may show different findings, further large-scale research is recommended to obtain countrywide estimates of the impact of social determinants of health on hearing outcomes in South Africa.