INTRODUCTION
Population aging has become a global phenomenon. According to the World Health Organization (WHO), by 2030, one in every six people around the world will be 60 years or older [1]. Aging is the primary factor contributing to hearing loss, which explains the increasing prevalence of this condition. The WHO has estimated that by 2050, over 900 million people will experience disabling hearing loss [2].
A substantial body of evidence indicates a correlation between hearing loss and cognitive decline [3,4], including reports suggesting an association with dementia [5-7]. Moreover, hearing loss that impedes communication can result in social isolation. Therefore, it is unsurprising that studies have linked hearing loss to feelings of loneliness [8], depression [9], anxiety [10], and a lower overall quality of life [11,12]. Furthermore, studies have demonstrated correlations between hearing loss and postural instability [13], falls [14], and gait [15]. Consequently, managing hearing loss is crucial for healthy aging, encompassing both mental and physical well-being.
The societal impact of age-related hearing loss is increasingly recognized, leading to growing concerns about the most effective management strategies. Currently, the most effective and widely used method to address age-related hearing loss is the use of hearing aids. Research has suggested that hearing rehabilitation through hearing aids may help reduce cognitive decline [16,17], the risk of falls [18], and even the risk of dementia [19]. A randomized controlled trial has shown that hearing aids can improve hearing-related quality of life and reduce symptoms of depression [20].
Despite the increasing prevalence of hearing loss and the numerous benefits of hearing aids, the uptake of these devices remains relatively low. Data from the 2020 Korea National Health and Nutrition Examination Survey (KNHANES) indicate that only 25.8% of individuals aged 65 and older with bilateral moderate or more severe hearing loss use hearing aids or cochlear implants. The primary barrier to adoption is the cost of hearing aids. A 2011 study found that approximately half of the individuals who did not use hearing aids cited high costs as the main reason for their decision [21]. This observation is supported by another study, which reported that an increase in government subsidies corresponded with a higher likelihood of hearing aid usage [22].
In light of the finite nature of economic resources and the significant financial strain that escalating healthcare costs place on society, it is crucial to assess the cost-effectiveness of hearing aids. A study utilized a multistate Markov model to evaluate the cost-effectiveness of hearing aids [23]. The findings indicated that, at a willingness-to-pay (WTP) threshold of $12,000 in Taiwan, the likelihood of hearing aids being cost-effective was 53% for women and 65% for men. Another study performed a cost-utility analysis on hearing aids for individuals with moderate to severe hearing loss. It found that if about 70% of users continued to use their hearing aids over 5 years, the incremental cost-effectiveness ratio (ICER) per quality-adjusted life year (QALY) would be 11,964 Singapore dollars [24]. A randomized controlled trial in China showed that using hearing aids led to an annual reduction of 243.34 yuan in healthcare costs. Additionally, the trial concluded that hearing aids were cost-effective when used for at least 2.52 years [25].
However, previous studies have focused exclusively on nations such as Taiwan [23], Singapore [24], and China [25], as well as individuals with at least moderate hearing loss [24,25]. Therefore, it is necessary to utilize recent data to investigate the cost-effectiveness of hearing aid use among individuals with mild hearing loss, who are still advised to use hearing aids. Consequently, this study aimed to evaluate the cost-effectiveness of hearing aid use across all levels of hearing loss for the first time in Korea.
MATERIALS AND METHODS
This study received an exemption from Institutional Review Board review (No. E-2308-134-1459). This retrospective study using national big data was exempted from the requirement for informed consent, as obtaining participant consent was not feasible.
Structure of the Markov model
A state-transition Markov model was employed to assess the cost-effectiveness of hearing aid utilization [26]. This model simulated a cohort of patients starting at age 50, progressing through normal, mild, moderate, and severe stages of hearing loss until death or age 80. The annual probabilities of changes in hearing status were based on the results of Chao and Chen [23]. The model was developed and analyzed using TreeAge software. Fig. 1 shows the structure of the model, which was adapted from the original model by Chao and Chen [23]. Once patients decided to use a hearing aid, they were assumed to continue using it until natural death or age 80. Full compliance was assumed in order to simplify the complex effects of dropout and reuse rates. The model is also based on sex- and age-specific mortality rates [27].
This study utilized the hearing thresholds proposed by the WHO in 1991. According to these criteria, mild hearing loss is characterized by an average threshold of 26–40 dB at 0.5, 1, 2, and 4 kHz in the better ear; moderate hearing loss by an average threshold of 41–60 dB; and severe hearing loss by an average threshold of 61–80 dB [28]. The condition of hearing loss either remains stable or progresses, regardless of hearing aid use. In adopting the societal perspective, the analysis included both direct medical costs and indirect costs, such as those related to productivity loss and travel expenses.
Included parameters
Costs
According to the Korea National Health Insurance Service (KNHIS), the mean annual number of clinic visits for hearing loss in the absence of a hearing aid prescription was calculated to be 2.30 in 2020. However, this statistic only reflects the average number of visits per person and does not include those who did not seek medical care. Therefore, it was necessary to include the likelihood of clinic visits in the calculation. The probability of visiting a clinic for individuals without hearing aids who experience hearing loss was derived from a study conducted in 2008 [23].
The respective costs were determined to be $4 for travel [29], $14 for a clinic visit, and $33 for a hearing test [30] in 2020. These figures were obtained from their representative sources. For each clinic visit, the productivity loss was assumed and calculated as half of the average daily income, which was $45 [31] in 2020.
The use of hearing aids involves several additional costs. These include the initial purchase price of the hearing aid, the cost of batteries, and any necessary repairs. The mean price of a hearing aid has been reported to be $1,373 [32]. Considering the subsidy provided every 5 years for purchasing hearing aids in Korea, the lifespan of a hearing aid was assumed to be 5 years, leading to an annual cost of $275. The annual costs for batteries and repairs, as reported by representatives from two major hearing aid vendors, Starkey and Resound, were $38 and $68, respectively. The financial impact doubled when both ears were equipped with hearing aids. Additionally, there were fees for hearing tests conducted while the patient wore the hearing aids. The cost for testing with a unilateral hearing aid was $23, whereas testing with bilateral hearing aids costs $33 [30]. The fee for fitting hearing aids was set at $68, based on the reimbursement of $339 by the KNHIS over a 5-year period.
According to data from the KNHIS, the average annual frequency of clinic visits among hearing aid users was 3.31 times in 2020. The proportion of users with binaural hearing aids reached 51% [33]. In 2020, the exchange rate was 1 dollar to 1180.0 won [34]. For a detailed account of the specific values and references, please refer to Table 1.
Effectiveness
The efficacy of hearing aid usage was quantified using the hearing-related QALY metric [35]. However, it is challenging to find appropriate reference values for the QALYs associated with various degrees of hearing loss and the efficacy of hearing aids. For our research, the study conducted by Landry et al. [36] proved to be particularly noteworthy due to its comprehensive and systematic analysis. For instance, the QALYs associated with hearing aids in the study by Landry et al. [36] varied across different degrees of hearing loss, unlike those reported by Chao and Chen [23]. Although some studies have suggested a link between hearing loss and increased mortality rates [37-39], we assumed that hearing loss or hearing aid use does not affect the lifespan. The discount rates for both costs and effects were set at an annual rate of 4.5%, in accordance with the guidelines established by the Health Insurance Review and Assessment Service [40].
Cost-utility analysis
The results of the cost-utility analysis are reported as the ICER, which is the difference in costs divided by the difference in QALYs.
Sensitivity analysis
A deterministic sensitivity analysis was conducted with the application of varying values to the parameters presented in Table 1. The cost range for hearing aids, set at $169 to $424, was sourced from Sim [32]. In the absence of sufficient data in the literature, an arbitrary range of 60% to 150% of the mean value was established for several parameters: hearing aid maintenance fees (including battery, repair, and fitting), the proportion of bilateral hearing aid use, hearing evaluation fees, clinic visit fees, annual clinic visit frequency, the probability of a clinic visit, travel expenses, productivity loss, and the discount rate. However, the range for the QALY was set between 60% and 120%, as it cannot exceed 1.
In addition, we modeled two different starting ages, 60 and 70 years, to represent cohorts with different transitions in hearing status and mortality. These choices allowed different cost-effectiveness results depending on different durations of hearing aid use at different starting ages. Probabilistic sensitivity analysis was also used to assess the robustness of the model results by considering the joint uncertainty of all parameters in the model. This involved sampling model parameter values from distributions of the variables in the model. We chose distributions that best represented the nature of the parameters involved. Specifically, a beta distribution was used for probabilities such as clinic visits and binaural hearing aid use, utility parameters, and the discount rate, which are bounded between 0 and 1. In contrast, we used a gamma distribution for cost and medical use parameters because this distribution is defined for non-negative values and is useful for modeling skewed data, which are common in cost data [26].
RESULTS
Table 2 presents the base-case cost-effectiveness results for male and female cohorts aged 50 years. The additional cost of hearing aids was $4,633, resulting in an increase of 0.54 QALYs for men. The corresponding ICER was $8,571, significantly below the WTP threshold of $31,721 (per capita gross domestic product [GDP] in 2020 [41]). The use of hearing aids for women yielded an ICER of $10,635, with an incremental cost of $5,422 and an incremental effectiveness of 0.51 QALYs.
Sensitivity analysis
Modifying the values of the parameters in the model did not change the conclusion that hearing aids are cost-effective. A decrease in the utility of hearing aid use and an increase in their cost led to the largest rise in ICERs; however, these values still fell below the WTP threshold for both men and women. Even when the use of hearing aids was delayed until ages 60 or 70, the ICERs remained under the WTP threshold, registering at $9,716 and $10,084 for men, and $10,529 and $10,444 for women, respectively. The results of the deterministic sensitivity analysis are illustrated in a tornado diagram (Fig. 2). Fig. 3 depicts the cost-effectiveness acceptability curve derived from the probabilistic sensitivity analysis. This analysis shows that the probabilities of cost-effectiveness were 83.6% for men and 73.4% for women at a WTP threshold of $31,721.
DISCUSSION
The prevalence of hearing loss is expected to rise sharply alongside an aging population. Hearing loss is linked not only to cognitive decline and social isolation but also to adverse physical and mental health outcomes. A systematic review indicates that in the United States, productivity losses and direct medical costs due to hearing impairment range from $1.8 billion to $194 billion and from $3.3 billion to $12.8 billion, respectively [42]. These findings suggest that the use of hearing aids could lead to reduced healthcare expenditures [25,43]. A global analysis by the WHO has shown that the social and economic costs of untreated hearing loss are estimated to be between $750 billion and $790 billion annually [44]. Additionally, the analysis suggests that proactive interventions for hearing loss could generate a return of approximately $15 for every $1 invested [45].
Our findings suggest that hearing interventions are cost-effective in Korea, where the costs of hearing aids and medical services are lower compared to other countries with a National Health Insurance Service. The ICERs for the men and women in Korea were $8,571 and $10,635, respectively. These figures decreased to $6,295 and $8,601 when using QALYs from Chao and Chen [23]. The ICERs are significantly below the WTP threshold of $31,721, which corresponds to the per capita GDP in 2020 [41] and is widely recognized as a benchmark by the WHO [46,47].
The lower ICERs for men can be explained by the earlier onset and faster progression of hearing loss in this group, which increase the potential benefits of hearing aids when used earlier in life. Differences between the sexes in biological and socio-economic factors are reflected in the model by differences in the transition of both hearing status and mortality. As expected, delaying hearing aid use until age 60 or 70 resulted in higher ICERs for men ($9,716 and $10,084, respectively), reflecting shorter duration of use and lower cumulative benefits.
Our ICER results are lower than or comparable to those reported in previous studies for Taiwan (United States Dollar [USD], 9,702–13,615), Singapore (SGD, 11,964), and China (USD, 33,587–11,180) [23-25]. Although the costs of hearing aids and medical services are similar to those in Taiwan under the National Health Insurance [48], the evaluation of hearing while wearing a hearing aid is less expensive in Korea. Furthermore, in Taiwan and Singapore, patients with hearing loss must schedule a separate appointment with an audiologist or hearing aid dispenser, incurring additional costs. In contrast, in Korea, these patients can have their hearing aid managed during their otolaryngologist appointment, eliminating the need for a separate consultation fee.
Our model assumed that once patients decided to use a hearing aid, they would continue to do so until either the end of their natural life or until they reached the age of 80. Kaur’s study [24] found that higher drop-out rates lead to an increased ICER. Ye et al. [25] assigned a 64% probability to the maintenance of hearing aids. As the retention period lengthened, the maintenance costs for hearing aids increased, yet the ICER decreased [25]. Therefore, it is necessary to consider our ICER results for the complete use case of the hearing aid.
A further challenge involves measuring QALYs in individuals with hearing loss. Researchers have emphasized that the impact of hearing loss on quality of life is highly multidimensional, involving numerous factors that are not accounted for in current utility measures [49,50]. Although our study employed two different QALY measures with great care, the use of more precise QALY measures that specifically account for hearing loss could prove beneficial in future cost-effectiveness assessments.
This study has several limitations. First, although we attempted to estimate and use as many Korean-specific parameters as the available data allowed, certain parameters, such as the transition probabilities proposed by Chao and Chen [23], had to be obtained from the previous literature. Second, where standard deviation values for certain variables were not available, we assumed these values to be one-tenth of the mean. The probabilistic sensitivity results remained consistent when these variables were assumed to be either one-fifth or one-twentieth of the mean. Third, subgroup analysis was restricted to sex and age to represent cohorts with different transitions in hearing status and mortality. Finally, caution should be exercised in extrapolating our findings from the Korean context, which has universal health insurance, to countries with different health care systems.
Hearing aids are highly cost-effective for adults aged 50 and above in Korea, regardless of the degree of hearing loss, even in mild cases. In light of the rapidly aging population, it would be prudent for government policymakers to consider the cost-effectiveness of hearing aids in their decision-making processes.
HIGHLIGHTS
▪ Hearing aids are a cost-effective intervention for both men and women aged 50 or older, with incremental cost-effectiveness ratios (ICERs) that are significantly lower than Korea’s per capita gross domestic product (GDP).
▪ Policy initiatives that promote the use of hearing aids could be a valuable investment in public health, improving the quality of life for older adults.
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