Abstract
This cohort study compares the incidence of sudden sensorineural hearing loss during the COVID-19 pandemic with that during 2018 and 2019 and assesses the association of lockdowns during the pandemic with sudden sensorineural hearing loss.
Sudden sensorineural hearing loss (SSNHL) is an emergency otologic condition with unknown pathophysiology that is mainly idiopathic. However, a viral cause was reported in temporal bone studies.1 Several reports have suggested that there is an increased risk of SSNHL after COVID-19.2 We aimed to compare the incidence of SSNHL during the COVID-19 pandemic with the incidence during 2018 and 2019 and to assess the association of lockdowns with incidence of SSNHL.
Methods
Using data from the Clalit Health Services (CHS), the largest health care provider in Israel (serving approximately 4.7 million people), we performed a retrospective cohort study with a nonconcurrent historic comparative group of individuals aged 16 years or older. The diagnosis of SSNHL was based on International Classification of Diseases, Ninth Revision codes in conjunction with a purchase of prednisone within 30 days after diagnosis. Observed cases of SSNHL documented from the beginning of the COVID-19 pandemic (March 1, 2020) to the introduction of the BNT162b2 messenger RNA COVID-19 vaccine (BioNTech/Pfizer) in Israel (December 19, 2020) were compared with the expected cases of SSNHL, estimated based on the experience of the CHS population in 2018 and 2019 during the same period. The study was approved by the institutional review board of the Lady Davis Carmel Medical Centre. Data were deidentified and owing to the retrospective nature of the study, a waiver of informed consent was granted by the institutional review board. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
Age- and sex-specific and adjusted standardized incidence ratios (SIRs) were calculated, and their 95% CIs were computed using the Mid-P exact test. To examine trends in SSNHL and its association with lockdowns, the weekly incident SSNHL cases during the 2020 study period were plotted and compared with the corresponding weekly incident cases during the same periods in 2018 and 2019. Similar comparisons were done for emergency department and community physician visits among adult members of the CHS.
Results
This study included 3 251 851 individuals (1 682 958 [51.7%] female; mean [SD] age, 45 [19.6] years) in 2020, 3 166 266 in 2018 (1 641 780 [51.8%] female; mean [SD] age, 45 [19.5] years), and 3 204 462 in 2019 (1 659 871 [51.8%] female; mean [SD] age, 45 [19.6] years). Compared with 2018 and 2019, there was a significant decrease in the incidence of SSNHL in 2020 during the COVID-19 pandemic before vaccine introduction. The sex- and age-weighted SIR was 0.80 (95% CI, 0.75-0.86) compared with 2018 and 0.78 (95% CI, 0.72-0.83) compared with 2019 (Table). The magnitude of SIRs was similar across both sex and examined age groups (Table). Comparing the distribution of weekly cases of SSNHL during the COVID-19 pandemic with that during the corresponding weeks in 2018 and 2019, we found a substantial decrease in documented SSNHL cases during and near the time of the first lockdown and a smaller decrease during the second lockdown (Figure, A). There was a significant decrease in emergency department and community physician visits during the first lockdown, followed by a small but steady decrease in emergency department visits during 2020 compared with 2018 and 2019 (Figure, B and C). However, the number of community physician’ visits was similar among all years after the first lockdown.
Table. Standardized Incidence Ratios for SSNHL During the COVID-19 Pandemic From March 1 Through December 19, 2020, Compared With the Same Period in 2018 and 2019a.
| Characteristic | Patients with SSNHL, No.b | Standardized incidence ratioc | |||
|---|---|---|---|---|---|
| 2020 Observed | 2018 Expected | 2019 Expected | 2020 vs 2018 | 2020 vs 2019 | |
| Age and sex weighted | 756 | 941.46 | 971.74 | 0.80 (0.75-0.86) | 0.78 (0.72-0.83) |
| Age, y | |||||
| Overall | |||||
| 16 to <45 | 171 | 206.34 | 206.30 | 0.83 (0.71-0.96) | 0.83 (0.71-0.96) |
| 45 to <65 | 210 | 281.59 | 298.56 | 0.75 (0.65-0.85) | 0.70 (0.61-0.80) |
| ≥65 | 375 | 453.06 | 466.77 | 0.83 (0.75-0.91) | 0.80 (0.72-0.89) |
| Age weighted | 756 | 940.99 | 971.62 | 0.80 (0.75-0.86) | 0.78 (0.72-0.83) |
| Female | |||||
| 16 to <45 | 86 | 103.26 | 103.18 | 0.83 (0.67-1.02) | 0.83 (0.67-1.02) |
| 45 to <65 | 97 | 132.97 | 144.60 | 0.73 (0.59-0.89) | 0.67 (0.55-0.81) |
| ≥65 | 169 | 209.79 | 239.33 | 0.81 (0.69-0.93) | 0.71 (0.60-0.82) |
| Age weighted | 352 | 446.02 | 487.11 | 0.79 (0.71-0.87) | 0.72 (0.65-0.80) |
| Male | |||||
| 16 to <45 | 85 | 103.09 | 103.11 | 0.82 (0.66-1.04) | 0.82 (0.66-1.01) |
| 45 to <65 | 113 | 148.83 | 154.04 | 0.76 (0.63-0.91) | 0.73 (0.61-0.88) |
| ≥65 | 206 | 243.52 | 227.48 | 0.85 (0.74-0.97) | 0.91 (0.79-1.04) |
| Age weighted | 404 | 495.44 | 484.63 | 0.82 (0.74-0.90) | 0.83 (0.75-0.92) |
The 2020 interval corresponds to the period of the COVID-19 pandemic before the introduction of the vaccine in Israel.
Expected numbers were estimated using the reference years.
With 2018 and 2019 as the reference years.
Figure. Weekly Distributions of Sudden Sensorineural Hearing Loss (SSNHL) Cases and Emergency Department (ED) and Physician Visits Among Adults From March 1 Through December 19, 2020, Compared With the Same Period in 2018 and 2019 in Israel.
The 2020 interval corresponds to the period of the COVID-19 pandemic before the introduction of the vaccine in Israel.
Discussion
This cohort study revealed a significant decrease in SSNHL during the COVID-19 pandemic in 2020 in Israel, particularly during the first lockdown. This finding may be associated with the decrease in visits to community physicians and emergency departments, as has been described with other life-threatening conditions, such as myocardial infarction.3 A similar decrease in the number of patients with SSNHL during the initial COVID-19 wave was reported at a single institute.4 As seen in our data, the number of physician community visits after the first lockdown in 2020 was similar to the numbers of visits in 2018 and 2019. In Israel, virtual visits to community physicians by telephone became available during the COVID-19 pandemic. Because SSNHL is abrupt and substantially impairs the conduct of normal life, it is less likely that patients ignore the symptoms when there is immediate availability of health care services.
Another explanation for these findings might be related to the substantial decrease in the occurrence of viral respiratory infections during the COVID-19 pandemic.5 The Israel Center of Disease Control reported that influenza was not detected in all sentinel clinics between March and December 19, 2020. This lack of cases was most likely associated with social distancing, lockdown, and the use of masks. A possible association between infectious diseases and SSNHL might be supported by the observation of a time-clustered presentation of SSNHL, suggesting an environmental or infectious cause.6 Although an attractive theory, if this were true, one would have expected that the occurrence of SSNHL would have remained low for the entire pandemic period because social distancing and face masks continued to be implemented, although to lesser extent later in 2020. The present study relied on data originally collected for administrative and clinical management and not specifically for the current study; thus, a possible limitation may be related to the quality of the data. In addition, International Classification of Diseases, Ninth Revision codes include only diagnosis of sensorineural hearing loss with no specific codes for SSNHL. However, to identify patients with SSNHL, our search included new diagnosis of hearing loss with a concurrent prednisone treatment, which is the standard of care for this condition. Therefore, the study did not include patients with SSNHL who were treated with intra-tympanic steroid injection as primary treatment in either 2020 or 2018 and 2019.
Reference
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