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LETTER TO THE EDITOR

Reply to the Comment on Mortality and Cause of Death in Hearing Loss Participants: A Longitudinal Follow-Up Study Using a National Sample Cohort

Kim, So Young M.D., Ph.D.; Kim, Hyung-Jong M.D., Ph.D.; Lee, Chang Ho M.D., Ph.D.; Sim, Songyong Ph.D.; Choi, Hyo Geun M.D., Ph.D.

Author Information
doi: 10.1097/MAO.0000000000002707
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In Reply: We appreciate the comments and agree to the opinion. As we described in the discussion section, it was limitations of our study that some variables, including duration of hearing impairment and the exposure to pesticides and agrochemicals, could not be considered. The indirect association of hearing impairment with mortality could not be totally excluded in the current data (1). The current results demonstrated the rate of mortality due to all causes were 4.03 times higher in severe hearing impairment patients than the control participants. The causality could not be delineated in the present study. To attenuate the confounder effects, the comorbidities were adjusted and the mortality rate was analyzed according to the cause of hearing impairment as presented in Table 4 (1).

As pointed by comments, Table 1 described the high proportion of subjects from the rural area in both severe and profound hearing impairment (59.7 and 65.1%, respectively) (1). Because the region of residence could influence to both hearing impairment and mortality due to the medical accessibility and environmental pollutants (2), the control groups were matched for the region of residence in this study. For the similar reason, the age, sex, and income were matched between hearing impairment and control groups. In addition, only the 1.97% (1,020,828/51,826,059) of Korean was engaged in agriculture according to the 2018 Korean Statistical Information Service (3). Most previous reports on the mortality in hearing impaired patients have limitations on the possible confounder effects due to the unconcerned environmental factors (4,5).

The heterogeneous types and durations of hearing impairment is another shortcoming of the present study. To attenuate the differences from the degree of hearing impairments, this study used the hearing handicap criteria of Korea. The potential relations between hearing impairment and mortality were discussed and these need to be tested in future randomized cohort study considered these possible confounders. However, the current study was in line with other studies suggested the contribution of hearing impairment of mortality and improved the previous findings by analyzed according to the cause of mortality. Although a few possible confounders was existed and the direct impact of hearing impairment on mortality could not be concluded, this study presented the higher rate of mortality in hearing impairment patients compared with control group, which might be clinically meaningful.

REFERENCES

1. Kim SY, Min C, Kim HJ, et al. Mortality and cause of death in hearing loss participants: a longitudinal follow-up study using a national sample cohort. Otol Neurotol 2020; 41:25–32.
2. Park M, Lee JS, Park MK. The effects of air pollutants on the prevalence of common ear, nose, and throat diseases in South Korea: A National Population-Based Study. Clin Exp Otorhinolaryngol 2019; 12:294–300.
3. Korean Statistical Information Service; 2018 Available at: http://kosis.kr/eng/index/index.do. Accessed April 8, 2020.
4. Lin HW, Mahboubi H, Bhattacharyya N. Hearing difficulty and risk of mortality. Ann Otol Rhinol Laryngol 2019; 128:614–618.
5. Davis A, McMahon CM, Pichora-Fuller KM, et al. Aging and hearing health: the life-course approach. Gerontologist 2016; 56: (suppl): S256–S267.
© 2020, Otology & Neurotology, Inc.