Hearing loss in elderly subjects, similar to most parts of the world, is not uncommon in Thailand. The prevalence of hearing disability, defined as a PTA > 40 dB in the better hearing ear in elder subjects, has been reported in different parts of the world to be approximately one-third of the elderly population.(2,39–42) In Thailand, the prevalence of hearing disability among elderly subjects was 24.40% in a previous study by Bunnag et al published in 2002(1). However, in our study, we found that the prevalence of hearing disability was higher, at 38.34% (risk difference = 13.90%). The external ear and middle ear pathology could contribute to the increasing of hearing disability prevalence. There were approximately 10 percent of participants in this study who had the external or middle ear pathology in either ear, half of them had PTA > 40 dB in the better hearing ear. Therefore, the otoscopy examination should be encouraged to confirm the diagnosis. The increase in the prevalence of hearing disability in this study could be explained by the differences in study settings and population. Our study was conducted in rural communities where the risk for loud noise exposure from agriculture machines is higher than in urban communities. Relevance to the study by Wang et al (43) which included the retired staff of an automobile manufactory, who may be more likely to have been exposed to loud noises in their prior environment, we found we have lower prevalence with a higher number of participants.
Presbycusis is the most common cause of hearing loss in the elderly population.(39) This process slowly progresses; hence, some elderly individuals with hearing loss do not realize the problem and therefore do not seek prompt medical attention. Diagnosis and rehabilitation can be delayed, especially in community-based patients. Earlier studies showed that only 7.5-10% of elderly individuals with hearing disability used hearing aids.(42,44) Hands reported a reduction in hearing handicap and an increase in overall hearing aid usage in elderly subjects in their cohort study of routine hearing screening performed with the HHIE-S in the elderly population.(45) Raising awareness of hearing problems by implementing feasible screening methods should lead to a higher number of elderly individuals receiving proper hearing rehabilitation. This is especially important in people with severe hearing loss (i.e., a PTA ≥ 60 dB) who are more likely to adopt the use of a hearing aid and have reported a higher QOL due to hearing rehabilitation. (46–48)
Ensuring that validated questionnaires are adopted and applied across different cultural contexts while retaining the reliability and validity of the original version is a challenge. For our study, we found that the reliability was very good for our Thai version and that our internal consistency was higher than that achieved by the Swedish version and comparable to that of the original version. The Cronbach’s alpha score for the HHIE-ST, the original version, the Japanese version and the Swedish version are 0.94, 0.82, 0.91 and 0.77, respectively.(23,27,49)
Regarding HHIE-ST scores and demographic data correlations, we found that mean scores were significantly correlated with age group, with older individuals having higher scores (p<0.001). There was no significant difference in HHIE-ST scores between sex or area of residence. However, there were significant differences in the total scores among groups with different levels of education, with higher scores received by participants with lower educational levels (p<0.001). We suggest that this could be related to the ability to understand the true meaning of the questions and the possibility that there are differences in self-awareness between these groups. Average hearing levels were worse in men than in women at every frequency and worsened with age, as expected, although these trends were not statistically significant.
Concerning the diagnostic value of this study, at a cut-off score 10 and a PTA BE higher than 40 dB, the sensitivity of HHIE-ST was 88.96%, slightly higher than that reported by Sindhusake et al(32) (80%) and Tomioka et al(27) (81.30%). The report of specificity was varied from 59 to 92% in other studies in the literature(23,27,29–33,50). In our study, the specificity was 52.19%. This result may reflect the influence of differences in culture, language, and religion.
Furthermore, a similar study in Thai population was done recently. Judee et al reported the sensitivity of HHIE-ST at a cut-off score 10 for detecting hearing disability was 69.7% and specificity was 74.9(51), which is lower sensitivity with higher specificity than in our study. This could be explained by the smaller number of participants than our study, 220 to 1109 participants. And the PTA in Judee et al study was calculated over the frequencies of 500, 1,000, and 2,000 Hz for the better ear hearing level, while we included 4,000 Hz in the PTA calculation for grading of hearing impairment according to WHO classification in our study.
Given all the reasons outlined above and according to the ROC curves shown in Table 3, we found that the HHIE-ST with the cut-off point 10 is sensitive for detecting Thai patients with moderate hearing loss who are targeted for hearing rehabilitation.
The diagnostic value of the A Single Question survey has been reported to range from 48-90% for sensitivity and 50-91% for specificity.(22,23,26,27,30,32,44,52–54) For the TSQ, we obtained a sensitivity of 88.73% and a specificity of 55.93% for detecting moderate hearing loss and a sensitivity of 95.56% and a specificity of 41.81% for screening for severe hearing loss. This result is similar to that found in a Japanese study(27) and the Blue Mountain study(32), which screened for moderate hearing loss; both of these studies also included more than one thousand participants, similar to our study.
We recommend that both the TSQ and the HHIE-ST are sensitive and useful for screening eligible hearing-disabled persons. However, we found that using the HHIE-ST in combination with the TSQ can increase specificity to 60.13% while sensitivity is still as high at 85.29%, as shown in Table 2. This is an effective screening method that could increase the detection rate and raise awareness for hearing rehabilitation in the hearing-disabled population.
The strength of this study is a large number of participants with varying educational levels and urban-rural community status. In addition, we conducted this study in a setting that accurately represents how the screening process would likely be done in a limited resource context. We performed the audiometry test in a sound-proof booth in the quietest area possible instead of using a sound-proof testing room, this could result in some error in the audiometry results. However, we conducted the test according to the WHO hearing measurement guidelines for nonclinical settings.(55) Hence, we believe that our study results should accurately represent the results that would be obtained in a general Thai elderly population when using these hearing screening tools and should present the least bias. In terms of how better results could be obtained with sensitivity and specificity, we recommend that language modification of a simplified questionnaire may be more appropriate for the Thai lifestyle.