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Article

The Risk of Developing Tinnitus and Air Pollution Exposure

by
Po-Yu Lai
1,†,
Chang-Yin Lee
2,3,4,†,
Kuang-Hsi Chang
5,6,7,
Yu-Kang Chang
5,8,
Yi-Chao Hsu
9,10,
Ing-Ming Chiu
11,
Stella Chin-Shaw Tsai
12,13,
Der-Yang Cho
11,14,15,
Cheng-Li Lin
16,17,
Tsung-Hsing Lin
18,* and
Wu-Lung Chuang
19,20,*
1
Department of Family Medicine, Tungs’ Taichung MetroHarbor Hospital, Taichung 435, Taiwan
2
College of Medicine, The School of Chinese Medicine for Post Baccalaureate, I-Shou University (Yancho Campus), Kaohsiung 824, Taiwan
3
Department of Chinese Medicine, E-DA Hospital, Kaohsiung 824, Taiwan
4
Department of Chinese Medicine, E-DA Cancer Hospital, Kaohsiung 824, Taiwan
5
Department of Medical Research, Tungs’ Taichung MetroHarbor Hospital, Taichung 435, Taiwan
6
Center for General Education, China Medical University, Taichung 404, Taiwan
7
General Education Center, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli 356, Taiwan
8
Department of Nursing, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli 356, Taiwan
9
Institute of Biomedical Sciences, Mackay Medical College, New Taipei City 252, Taiwan
10
Department of Audiology and Speech-Language Pathology, Mackay Medical College, New Taipei City 252, Taiwan
11
Institute of Biomedical Sciences, China Medical University, Taichung 402, Taiwan
12
Department of Otolaryngology, Tungs’ Taichung MetroHarbor Hospital, Taichung 435, Taiwan
13
Rong Hsing Research Center for Translational Medicine, College of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan
14
Translational Cell Therapy Center, Department of Medical Research, China Medical University Hospital, Taichung 404, Taiwan
15
Department of Neurosurgery, China Medical University Hospital, Taichung 404, Taiwan
16
Management Office for Health Data, China Medical University Hospital, Taichung 404, Taiwan
17
College of Medicine, China Medical University, Taichung 404, Taiwan
18
Department of Emergency Medicine, Kuang Tien General Hospital, Taichung 433, Taiwan
19
Division of Endocrinology and Metabolism, Department of Internal Medicine, Changhua Christian Hospital, Changhua 500, Taiwan
20
Division of Endocrinology and Metabolism, Department of Internal Medicine, Lukang Christian Hospital, Changhua 505, Taiwan
 
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*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Atmosphere 2025, 16(5), 618; https://doi.org/10.3390/atmos16050618
Submission received: 16 April 2025 / Revised: 7 May 2025 / Accepted: 12 May 2025 / Published: 19 May 2025
(This article belongs to the Special Issue Air Pollution Exposure and Health Impact Assessment (3rd Edition))
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Abstract

:
(1) Background: The role of air pollutants as risk factors for tinnitus remains unclear. To address this gap in research, we conducted a nationwide retrospective cohort study in Taiwan by integrating patients’ clinical data with daily air quality data to evaluate the environmental risk factors associated with tinnitus. (2) Methods: The Taiwan National Health Research Database (NHIRD) includes medical records for nearly all residents of Taiwan. To assess pollution levels, we used daily air quality data from the Taiwan Environmental Protection Agency regarding SO2, CO, NO, NOX, and particulate matter (PM2.5 and PM10). We merged the NHIRD data with air quality information based on the residents’ locations and the positions of air quality monitoring stations. Pollutant levels were then categorized into quartiles (Q1, Q2, Q3, and Q4). (3) Results: This study included 284,318 subjects. After controlling for covariates, the adjusted HR (95 CI%) for tinnitus increased with increasing SO2, CO, NO, NOX, PM2.5, and PM10 exposure levels, specifically from 1.24 (95 CI% = 1.18, 1.30) to 1.35 (95 CI% = 1.28–1.41); from 1.15 (95 CI% = 1.09, 1.21) to 1.90 (95 CI% = 1.81, 2.00); from 0.86 (95 CI% = 0.82, 0.91) to 1.69 (95 CI% = 1.62, 1.77); from 1.62 (95 CI% = 1.54, 1.71) to 1.69 (95 CI% = 1.60, 1.77); from 0.16 (95 CI% = 0.15, 0.18) to 2.70 (95 CI% = 2.57, 2.84); and from 2.53 (95 CI% = 2.38, 2.69) to 3.58 (95 CI% = 3.39, 3.78), respectively, compared to the Q1 concentrations for all air pollutants. (4) Conclusions: During the 15-year follow-up period, we found a significant positive correlation between air pollutant exposure and the risk of tinnitus.

1. Introduction

Due to the accelerating pace of industrialization and urban development in many countries worldwide, the degradation of air quality—particularly as a result of heavy vehicular traffic—has emerged as a pressing public health concern [1,2,3]. The growing number of automobiles, coupled with industrial emissions and inadequate urban planning, has led to elevated levels of airborne pollutants in densely populated regions [4,5]. Numerous studies have documented the detrimental effects of air pollution on human health, linking exposure to fine particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and other pollutants with a broad spectrum of medical conditions. These include systemic inflammation, oxidative stress, and the exacerbation or development of chronic illnesses such as respiratory diseases (e.g., asthma and chronic obstructive pulmonary disease), cardiovascular diseases, cerebrovascular events, and neurodegenerative disorders [6,7,8,9,10,11,12,13]. Among the range of health outcomes potentially influenced by environmental exposures is tinnitus, a prevalent and often persistent medical condition characterized by the perception of sound in the absence of an external auditory stimulus [14,15]. Tinnitus can manifest as ringing, buzzing, or hissing sensations, and although it may be transient or mild in some individuals, it can be chronic and debilitating in others [16,17]. Several risk factors have been associated with the onset or worsening of tinnitus, including lifestyle behaviors such as obesity, smoking, and alcohol consumption, as well as medical history variables such as head trauma, arthritis, and hypertension [18,19,20,21,22,23]. Despite being more common among older adults, tinnitus can affect individuals of all ages and has been identified as a symptom that significantly disrupts daily functioning and overall well-being [24,25,26]. Though tinnitus only severely affects a subset of those who experience it, its impact on quality of life can be substantial [25]. Affected individuals may report disturbances in emotional and psychological well-being, including symptoms of anxiety and depression, as well as challenges related to sleep, concentration, and communication [27,28,29,30,31,32,33,34]. In many cases, tinnitus necessitates lifestyle adjustments and contributes to a reduction in overall life satisfaction and perceived health [35]. While considerable research has focused on identifying biological, psychological, and environmental contributors to tinnitus, the condition’s multifactorial etiology continues to present challenges for clinicians and researchers alike [36].
Traditionally, air pollution and tinnitus have been treated as distinct public health issues. Air pollution, with its well-established links to mortality and morbidity across organ systems, has prompted global health initiatives aimed at emission reduction and environmental sustainability [37]. Tinnitus, on the other hand, has primarily been approached from an audiological and neurological standpoint. However, emerging evidence suggests that these two seemingly unrelated issues may share underlying mechanisms and health pathways. Recent epidemiological studies have begun to examine the association between exposure to air pollutants and auditory disorders, identifying links to conditions such as sudden sensorineural hearing loss and Meniere’s disease [38,39,40,41,42]. These findings point toward a possible influence of environmental factors—including air quality—on inner ear and neural auditory function [43,44].
Despite these advances, research specifically addressing the relationship between long-term exposure to air pollution and the incidence of tinnitus remains limited. The lack of large-scale, longitudinal data on this topic hinders the ability to draw definitive conclusions or implement evidence-based public health interventions. To address this gap in the literature, we conducted a nationwide retrospective cohort study in Taiwan, leveraging a comprehensive health database to examine whether chronic exposure to ambient air pollutants is associated with an elevated risk of developing tinnitus. This study contributes novel insights into the environmental determinants of tinnitus and can inform future public health policies aimed at mitigating the burden of this condition.

2. Materials and Methods

2.1. Data Sources

Two databases were used: the 2005 Longitudinal Generation Tracking Database (LGTD 2005) and the Taiwan Air Quality Monitoring Database (TAQMD). The LGTD 2005 included two million residents randomly selected from the original 2005 registry for beneficiaries joining the Taiwan National Health Insurance (NHI) program. The NHI program in Taiwan was launched on 1 March 1995, and provides coverage to more than 23 million residents in Taiwan. Disease coding follows the International Classification of Diseases, Ninth Revision, Tenth Revision, and Clinical Modification (ICD-9-CM and ICD-10-CM). The Taiwan Environmental Protection Administration Executive Yuan established the TAQMD to record daily air pollution concentrations from 74 ambient air quality monitoring stations on Taiwan Island. We combined and stratified the LGTD 2005 and TAQMD by residential areas linked to nearby air quality monitoring stations. The living area of the insured persons was defined based on the treatment sought for acute upper respiratory tract infection (AURTI) (ICD-9-CM code 460; ICD-9-CM code J00). This study was approved by the Institutional Review Board of the Research Ethics Committee of China Medical University Hospital (CMUH109-REC2-031(CR-3)).

2.2. Study Population, Outcome, and Comorbidities

The study cohort was determined according to the residential addresses of insured individuals on 1 January 2005, which served as the index date for the research. We excluded insurants with a history of tinnitus (ICD-9-CM codes: 388.30, 388.31, and 388.32; ICD-10-CM codes: H93.11, H93.12, H93.13, and H93.19) before the index date. The follow-up endpoints included either the date of withdrawal from the NHI program, the onset of tinnitus, or 31 December 2017. For each participant, daily average concentrations of air pollutants were computed from 2003 through the end of the observation period. These concentrations were then divided into four quartile-based levels: SO2 concentration (first quartile [Q1]: <3.64, second quartile [Q2]: 3.64–4.61, third quartile [Q3]: 4.62–5.30, and fourth quartile [Q4]: >5.30 ppb), CO concentration (first quartile [Q1]: <0.49, second quartile [Q2]: 0.50–0.61, third quartile [Q3]: 0.62–0.78, and fourth quartile [Q4]: >0.78 ppm), NO concentration (Q1: <4.15, Q2: 4.15–7.31, Q3: 7.32–10.0, and Q4: >10.0 ppb), NOx concentration (Q1: <21.7, Q2: 21.7–28.1, Q3: 28.2–37.8, and Q4: >37.8 ppb), PM2.5 concentration (Q1: <27.6, Q2: 27.6–29.1, Q3: 29.2–36.3, and Q4: >36.3 μg/m3), and PM10 concentration (Q1: <51.7, Q2: 51.7–55.6, Q3: 55.7–66.4, and Q4: >66.4 μg/m3). We considered sex, age, urbanization level, alcohol abuse or dependence, tobacco abuse or dependence, chronic obstructive pulmonary disease (COPD), asthma, obesity, osteoporosis, temperature, and humidity as the confounding factors in this study.

2.3. Statistical Analysis

Categorical variables, including sex, urbanization level, comorbidities, and outcome, are expressed as numbers and percentages. Continuous variables, including age, temperature, humidity, and exposure to air pollutants, are presented as means and standard deviations. The incidence rate (IR) of tinnitus (per 1000 person-years) was calculated for different air pollutants. Univariate and multivariate Cox proportional hazard regression models were used to calculate hazard ratios for tinnitus in Q2–Q4 concentrations of air pollutants compared with concentrations in Q1. SAS software (version 9.4; SAS Institute Inc., Cary, NC, USA) was used in this study, and a two-sided p-value of <0.05 was considered significant.

3. Results

A total of 223,544 participants were enrolled in this study (Table 1); 54.4% were female, and the average age was 39.6 ± 15.5 years. The highest level of urbanization (Level 1) accounted for 64.29% of the total. The percentage of participants with COPD, asthma, and osteoporosis were 26,453 (12.39%), 27,949 (13.09%), and 16,604 (7.78%), respectively. The daily average concentrations of SO2, CO, NO, NOx, PM2.5, and PM10 were 4.66 ± 1.67 ppb, 0.68 ± 0.29 ppm, 10.2 ± 11.0 ppb, 32.4 ± 16.9 ppb, 31.7 ± 7.73 µg/m3, and 58.7 ± 12.4 µg/m3, respectively. At the end of the study, 9401 (4.4%) participants had developed tinnitus during the study period. The mean follow-up time was 16.1 ± 2.76 years.
The incidence rates (IRs), crude hazard ratios (cHRs), and 95% confidence intervals of tinnitus for SO2, CO, NO, NOx, PM2.5, and PM10 are presented in Table 2 and stratified into quartiles. The IR of tinnitus increased from Q1 to Q4 for SO2, CO, NO, NOx, PM2.5, and PM10, specifically from 1.93 to 5.29; from 2.13 to 6.19; from 2.13 to 3.4; from 1.77 to 3.62; from 0.65 to 6.46; and from 1.10 to 6.19 per 1000 person-years, respectively.
After controlling for age, sex, urbanization level, and comorbidities of alcohol abuse/dependence, tobacco abuse/dependence, COPD, asthma, temperature, and humidity, the adjusted HR (95 CI%) for tinnitus increased with increasing SO2, CO, NO, NOx, PM2.5, and PM10 exposure levels, specifically from 1.25 (95 CI% = 1.17, 1.34) to 2.75 (95 CI% = 2.60–2.91); from 1.11 (95 CI% = 1.044, 1.18) to 3.13 (95 CI% = 2.95, 3.33); from 1.31 (95 CI% = 1.23, 1.39) to 1.76 (95 CI% = 1.66, 1.86); from 1.57 (95 CI% = 1.47, 1.67) to 2.24 (95 CI% = 2.11, 2.39); from 1.29 (95 CI% = 1.17, 1.46) to 9.26 (95 CI% = 8.58, 9.99); and from 0.36 (95 CI% = 0.32, 0.41) to 5.23 (95 CI% = 4.89, 5.58), respectively, compared to the Q1 concentrations for all air pollutants (Table 3).
Figure 1 illustrates the positive association between exposure to higher concentrations of SO2, CO, NO, NOX, PM2.5, and PM10 and an increased incidence of tinnitus, relative to lower exposure levels. Across all pollutants examined, elevated ambient air pollution concentrations were consistently associated with an increased risk of tinnitus, suggesting a dose–response relationship.
Pearson coefficients were highest between NOx and NO (r = 0.977) and NOx and CO (r = 0.940), moderate for SO2 with NOx (r = 0.640) and NO (r = 0.581), and strong between PM2.5 and PM10 (r = 0.923), with low correlations between gaseous and particulate pollutants (Table S1). Table S2 show the per-unit exposure–tinnitus associations. After adjustment, each 1 ppb increase in SO2 corresponded to aHR 1.25 (95% CI 1.23–1.26), each 1 ppm CO to aHR 2.25 (2.11–2.39), each 1 ppb NO and NOx to aHR 1.01 (1.008–1.01 and 1.01–1.012, respectively), each 1 µg/m3 PM2.5 to aHR 1.12 (1.11–1.12), and each 1 µg/m3 PM10 to aHR 1.06 (1.05–1.06). In median-stratified subgroup analyses, participants with pollutant levels at or above the median showed significantly higher adjusted tinnitus hazards across demographic and comorbidity strata (Tables S3–S8). In females versus males, aHRs were: SO2 ≥ 4.61 ppb (Table S3): 1.72 (1.63–1.82) vs. 1.44 (1.36–1.54); CO ≥ 0.61 ppm (Table S4): 1.67 (1.58–1.77) vs. 1.54 (1.44–1.64); NO ≥ 7.31 ppb (Table S5): 1.20 (1.14–1.27) vs. 1.13 (1.06–1.20); NOx ≥ 28.1 ppb (Table S6): 1.55 (1.47–1.64) vs. 1.44 (1.36–1.54); PM2.5 ≥ 29.1 µg/m3 (Table S7): 6.89 (6.37–7.46) vs. 6.01 (5.51–6.56); PM10 ≥ 55.6 µg/m3 (Table S8): 5.61 (5.20–6.04) vs. 4.83 (4.45–5.24). Across age, urbanization, and comorbidity subgroups, elevated pollutant exposures conferred 20–150% greater risk for gaseous pollutants and 4–17-fold for particulate matter. Effect sizes were generally larger in younger adults, females, and lower-urbanization areas, and modestly attenuated among participants with baseline respiratory or metabolic conditions.

4. Discussion

Accumulating evidence indicates that air pollution is associated with the incidence of sensorineural hearing loss (SNHL) [39,40,45,46,47]. However, it is still unclear whether air pollution is associated with the incidence of tinnitus. Tinnitus is defined as the perception of sound without additional external stimuli. It is usually accompanied by different types of SNHL, such as noise-induced and age-related SNHL. In the present study, we further tested the hypothesis of an association between air pollution and tinnitus using two large longitudinal databases to evaluate the risk of tinnitus in Taiwanese residents exposed to air pollution. During the 15-year follow-up period, we enrolled 284,318 residents (13,882 with tinnitus and 270,436 with SNHL) and found a significant positive correlation between air pollutant exposure and the risk of tinnitus.
Tinnitus has been associated with an increased incidence of depression and anxiety [48,49,50]. A previous study enrolled a total of 566 patients with tinnitus to evaluate depression and anxiety symptoms, both of which have been suggested as significant targets for the management of suicidal ideation [48]. Lin et al. also reported a significant association between tinnitus and the risk of depression in the adult population of the United States and suggested that the clinical management of tinnitus requires consideration of psychological factors [49]. Another prospective study evaluating 600 enrolled patients with mild-to-moderate tinnitus also indicated a significant correlation between the degree of SNHL and anxiety/depression scores in these patients [50]. Tinnitus has also been associated with an increased incidence of dementia [51,52,53]. Cheng et al. reported that in the young and middle-aged populations, pre-existing tinnitus increased the risk of developing early-onset dementia by 68%, indicating an urgent need for raising awareness of tinnitus as a potential harbinger for future dementia in these populations [51]. Notably, compared to dementia patients without any history of auditory symptoms, patients with tinnitus or hyperacusis had relatively preserved gray matter in the posterior superior temporal lobe but reduced gray matter in the orbitofrontal cortex and medial geniculate nucleus. Therefore, tinnitus may be a significant risk factor for dementia [53].
The concentrations of pollutants were divided into four quartile-based levels. The adjusted hazard ratio for PM2.5 in the second quartile (0.16; 95% CI: 0.15–0.18) was significantly low and inconsistent with the trends observed in higher quartiles. Several factors may contribute to this outcome. First, our data show that the study population was heavily concentrated near the upper limit of the first quartile (25.49 μg/m3) for PM2.5. As a result, the number of individuals exposed to PM2.5 levels in the second quartile—and who subsequently developed tinnitus—was lower compared to those exposed to other pollutants. Second, PM2.5 may have a threshold effect whereby health risks only begin to increase once exposure exceeds a certain level. However, the use of quartile-based categorization for pollutant exposure is methodologically limiting. Arbitrary cutoffs reduce interpretability, mask dose–response relationships, and limit comparability to established regulatory thresholds.
This cohort study was meticulously designed and featured an extended follow-up duration with adjustments for diverse confounding factors. However, this study had certain limitations. First, the primary constraints of the NHIRD study pertain to the absence of occupational noise exposure, stress, and information on healthy behaviors and dietary habits. The lack of these covariates does create potential bias. However, several studies suggested that urbanization is highly correlated with the above covariates [54,55,56,57,58]; therefore, we consider urbanization as a proxy covariate in multivariate analysis to minimize potential bias. The diagnostic criteria for alcohol abuse/dependence rely on drinking behavior and patient attitudes. Previous NHIRD studies have focused on COPD, asthma, and tobacco abuse/dependence instead of assessing smoking status [12,39,40,59,60,61,62,63]. Therefore, we regarded COPD, asthma, tobacco abuse/dependence, and alcohol abuse/dependence as surrogate variables for assessing smoking status and alcohol consumption. However, the reported prevalence of COPD, asthma, and tobacco abuse/dependence may be affected by underreporting.
Second, there could be surveillance bias at play, potentially linked to the level of urbanization and its association with medical accessibility. This could lead to the varying prevalence rates of tinnitus in urban and rural areas. Notably, the Taiwanese government has implemented a single-payer compulsory social insurance system that encompasses over 99% of residents. This system helps to equalize medical accessibility between urban and rural regions by offering free medical care [64,65]. Third, while indoor air pollutant levels are linked to building characteristics [66], their concentration was not assessable in this nationwide study. However, there is no evidence suggesting variations in building characteristics among locations with different air pollution levels in Taiwan, nor is there any evidence indicating that buildings cannot effectively block outdoor air pollutants [67,68]. Nevertheless, further research is needed to elucidate the influence of indoor air quality. Fourth, due to the Personal Data Protection Act, we are unable to obtain the study participants’ addresses and activity areas from the database. Therefore, the participants’ residential area was determined based on the location of the institution where they sought medical attention for acute upper respiratory tract infections (URTIs), throughout the study period. In the United States, URTIs represent the most prevalent category of infectious diseases, with adults experiencing an estimated three episodes annually [69]. Defining residential areas based on patterns of healthcare utilization, as employed in this study, is considered a more accurate approach than relying on administrative insurance registration data, particularly in evaluating accessibility to medical resources [70]. Furthermore, evidence supports the notion that individuals typically seek care for upper respiratory tract infections (URTIs) within or near their residential zones, and that long-distance travel for such care is uncommon [71]. However. individuals without medical records during this period were excluded, and this group tended to reside in regions characterized by low levels of air pollutants. This could lead to an underestimation of the risk of tinnitus. Nevertheless, potential misclassification bias remains. Fifth, although this study featured a long follow-up period, misclassification resulting from tinnitus developing after the study period may have led to an underestimation of tinnitus risk. Finally, the air pollution levels in the residential areas of the NHIRD insurants were evaluated using data from the closest air quality monitoring stations to clinics or hospitals. This methodology may introduce bias into the findings, given that the measured air quality and urbanization levels could diverge from the actual values, especially in cases where participants have lengthy commutes between their homes and medical facilities. Therefore, additional personal air sampling should be conducted to confirm these observations.

5. Conclusions

This is the first nationwide, population-based cohort study investigating the association between air pollution and tinnitus. Our findings suggest that increased exposure to air pollution is associated with a higher risk of tinnitus. Future research should incorporate personal air sampling to validate and further explore these observations.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/atmos16050618/s1, Table S1. Pearson’s Correlation Coefficient among air pollutants; Table S2. The risk of Tinnitus in patients and associated HRs in participants exposed to daily average concentrations of various air pollutants; Table S3. Comparison of incidence and hazard ratio of Tinnitus stratified by gender, age, and comorbidity between SO2 < 4.61 (median) and SO2 ≧ 4.61 (median); Table S4. Comparison of incidence and hazard ratio of Tinnitus stratified by gender, age and comorbidity between CO < 0.61 (median) and CO ≧ 0.61 (median); Table S5. Comparison of incidence and hazard ratio of Tinnitus stratified by gender, age and comorbidity between NO < 7.31 (median) and NO ≧ 7.31 (median); Table S6. Comparison of incidence and hazard ratio of Tinnitus stratified by gender, age and comorbidity between NOx < 28.1 (median) and NOx ≧ 28.1 (median); Table S7. Comparison of incidence and hazard ratio of Tinnitus stratified by gender, age and comorbidity between PM2.5 < 29.1 (median) and PM2.5 ≧ 29.1 (median); Table S8. Comparison of incidence and hazard ratio of Tinnitus stratified by gender, age and comorbidity between PM10 < 55.6 (median) and PM10 ≧ 55.6 (median).

Author Contributions

Conceptualization, K.-H.C., P.-Y.L., S.C.-S.T. and Y.-C.H.; methodology, K.-H.C. and C.-L.L.; software, K.-H.C. and C.-L.L.; validation, P.-Y.L., C.-Y.L., K.-H.C., Y.-K.C., Y.-C.H., I.-M.C., S.C.-S.T., D.-Y.C., C.-L.L., T.-H.L. and W.-L.C.; formal analysis, K.-H.C., Y.-K.C. and C.-L.L.; investigation, P.-Y.L., C.-Y.L., K.-H.C., Y.-K.C., Y.-C.H., I.-M.C., S.C.-S.T., D.-Y.C., C.-L.L., T.-H.L. and W.-L.C.; resources, D.-Y.C. and K.-H.C.; data curation, K.-H.C., Y.-K.C., S.C.-S.T. and Y.-C.H.; writing—original draft preparation, K.-H.C., P.-Y.L., S.C.-S.T. and Y.-C.H.; writing—review and editing, K.-H.C.; visualization, all authors; supervision, K.-H.C., P.-Y.L., S.C.-S.T. and Y.-C.H.; project administration, D.-Y.C. and S.C.-S.T.; funding acquisition, D.-Y.C. and S.C.-S.T. All authors have read and agreed to the published version of the manuscript.

Funding

This study is supported in part by Taiwan Ministry of Health and Welfare Clinical Trial Center (MOHW113-TDU-B-212-114009), China Medical University Hospital (DMR-111-105; DMR-112-087; DMR-113-009; DMR-113-156; DMR-114-139), and Tungs’ Taichung Metroharbor Hospital (TTMHH-R1120012/R1130051/R1140020/R1140024/R140025/R140037/R1140083/R1140085).

Institutional Review Board Statement

The NHIRD safeguards patient personal information through encryption to ensure privacy protection and assigns researchers anonymous identification numbers linked to pertinent claims data such as gender, date of birth, medical services, and prescriptions. Consequently, accessing the NHIRD does not necessitate patient consent. This research project received approval for exemption from the Institutional Review Board (IRB) at China Medical University (Approval Number CMUH109-REC2-031(CR-3)), and the IRB explicitly waived the requirement for consent. All procedures adhered to the applicable guidelines and regulations. The requirement for informed consent was waived by the Ethics Committee of the Institutional Review Board (IRB) at China Medical University because of the retrospective nature of the study.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are accessible through the National Health Insurance Research Database (NHIRD) provided by the Taiwan National Health Insurance (NHI) Administration. However, due to the Personal Information Protection Act enforced by the Taiwan government, these data cannot be publicly released. If you wish to obtain these data, you can submit an official request through the NHIRD website at https://dep.mohw.gov.tw/DOS/lp-2506-113.html (accessed on 15 May 2025).

Acknowledgments

We are grateful to the Health Data Science Center, China Medical University Hospital, for providing administrative, technical, and funding support. The funders had no role in the study design, data collection and analysis, the decision to publish, or the preparation of the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
LGTDLongitudinal Generation Tracking Database
TAQMDTaiwan Air Quality Monitoring Database
IRRincidence rate ratio
aHRadjusted hazard ratio
cHRcrude hazard ratio
CIconfidence interval
SO2sulfur dioxide
COcarbon monoxide
NOnitric oxide
NOxnitrogen oxide
PMparticulate matter
NHIRDNational Health Insurance Research Database
COPDchronic obstructive pulmonary disease

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Atmosphere 16 00618 g001
Figure 1. Kaplan–Meier curves depicting the cumulative incidence of tinnitus over the follow-up period for each quartile of air pollutant exposure.
Figure 1. Kaplan–Meier curves depicting the cumulative incidence of tinnitus over the follow-up period for each quartile of air pollutant exposure.
Atmosphere 16 00618 g001
Table 1. Baseline demographics and air pollutant exposure by yearly average concentration in Taiwan, 2003–2021.
Table 1. Baseline demographics and air pollutant exposure by yearly average concentration in Taiwan, 2003–2021.
N = 213,544Groupsn%
GenderFemale116,08254.4
Male97,46245.6
Age, yearsMean, SD39.615.5
Urbanization level †1 (highest)137,28864.29
258,41427.35
315,4607.24
4 (lowest)23821.12
Comorbidity
Alcohol abuse/dependenceYes46072.16
Tobacco abuse/dependenceYes14,1536.63
COPDYes26,45312.39
Asthma Yes27,94913.09
ObesityYes55832.61
OsteoporosisYes16,6047.78
Exposure to air pollutants
SO2 level (daily average, ppb)Mean, SD4.661.67
CO level (daily average, ppm)Mean, SD0.680.29
NO level (daily average, ppb)Mean, SD10.211.0
NOx level (daily average, ppb)Mean, SD32.416.9
PM2.5 (daily average, μg/m3)Mean, SD31.77.73
PM10 (daily average, μg/m3)Mean, SD58.712.4
Outcome
TinnitusYes94014.4
Follow-up time, years Mean, SD16.12.76
Urbanization level † was categorized by the population density of each residential area into four levels, with level 1 being the most urbanized and level 4 being the least urbanized. COPD, chronic obstructive pulmonary disease; CO, carbon monoxide; NO, nitric oxide; NOx, nitrogen oxides; SD, standard deviation.
Table 2. Incidence rates and crude hazard ratios of tinnitus across quartiles of pollutant levels.
Table 2. Incidence rates and crude hazard ratios of tinnitus across quartiles of pollutant levels.
PollutantsLevelsEventIRcHR(95%CI)
SO2 (ppb)Quartile 1, <3.6416991.931.00Ref
Quartile 2, 3.64–4.6119882.391.24(1.16, 1.32)
Quartile 3, 4.62–5.3013331.480.76(0.71, 0.82)
Quartile 4, >5.3043815.292.75(2.60, 2.91)
CO (ppm)Quartile 1, <0.4916582.131.00Ref
Quartile 2, 0.50–0.6119482.211.04(0.97, 1.11)
Quartile 3, 0.61–0.7825012.000.94(0.88, 1.00)
Quartile 4, >0.7832946.192.93(2.76, 3.11)
NO (ppb)Quartile 1, <4.1518052.131.00Ref
Quartile 2, 4.15–7.3123342.731.29(1.21, 1.37)
Quartile 3, 7.31–10.015032.361.11(1.04, 1.19)
Quartile 4, >10.037593.41.6(1.52, 1.70)
NOx (ppb)Quartile 1, <21.714711.771.00Ref
Quartile 2, 21.7–28.124752.721.54(1.44, 1.64)
Quartile 3, 28.1–37.820012.681.51(1.41, 1.62)
Quartile 4, >37.834543.622.05(1.93, 2.18)
PM2.5 (μg/m3)Quartile 1, <27.67920.651.00Ref
Quartile 2, 27.6–29.15150.861.33(1.19, 1.48)
Quartile 3, 29.1–36.331973.725.75(5.32, 6.21)
Quartile 4, >36.348976.4610(9.36, 10.88)
PM10 (μg/m3)Quartile 1, <51.7 10811.101.00Ref
Quartile 2, 51.7–55.63140.390.36(0.31, 0.40)
Quartile 3, 55.7–66.429153.473.15(2.93, 3.37)
Quartile 4, >66.450916.195.65(5.29, 6.04)
IR, incidence rate (per 1000 person-years); cHR, crude hazard ratio; CI, confidence interval. Daily average air pollutant concentrations were categorized into four groups based on the quartiles for each air pollutant.
Table 3. The risk of tinnitus in patients exposed to various air pollutants stratified by quartile of daily average concentration using Cox proportional hazard regression.
Table 3. The risk of tinnitus in patients exposed to various air pollutants stratified by quartile of daily average concentration using Cox proportional hazard regression.
PollutantsLevelsaHR #(95%CI)
SO2 (ppb)Continuous1.25(1.23, 1.26)
Quartile 1, <3.641.00Ref
Quartile 2, 3.64–4.611.25(1.17, 1.34)
Quartile 3, 4.62–5.300.83(0.77, 0.89)
Quartile 4, >5.302.75(2.60, 2.91)
CO (ppm)Continuous2.25(2.11, 2.39)
Quartile 1, <0.491.00Ref
Quartile 2, 0.50–0.611.11(1.04, 1.18)
Quartile 3, 0.61–0.781.06(0.99, 1.13)
Quartile 4, >0.783.13(2.95, 3.33)
NO (ppb)Continuous1.01(1.008, 1.01)
Quartile 1, <4.151.00Ref
Quartile 2, 4.15–7.311.31(1.23, 1.39)
Quartile 3, 7.31–10.01.19(1.11, 1.27)
Quartile 4, >10.01.76(1.66, 1.86)
NOx (ppb)Continuous1.01(1.01, 1.012)
Quartile 1, <21.71.00Ref
Quartile 2, 21.7–28.11.57(1.47, 1.67)
Quartile 3, 28.1–37.81.60(1.50, 1.72)
Quartile 4, >37.82.24(2.11, 2.39)
PM2.5 (μg/m3)Continuous1.12(1.11, 1.12)
Quartile 1, <27.61.00Ref
Quartile 2, 27.6–29.11.31(1.17, 1.46)
Quartile 3, 29.1–36.35.40(5.00, 5.84)
Quartile 4, >36.39.26(8.58, 9.99)
PM10 (μg/m3)Continuous1.06(1.05, 1.06)
Quartile 1, <51.71.00Ref
Quartile 2, 51.7–55.60.36(0.32, 0.41)
Quartile 3, 55.7–66.43.07(2.87, 3.30)
Quartile 4, >66.45.23(4.89, 5.58)
aHR, adjusted hazard ratio; CI, confidence interval. Daily average air pollutant concentrations were categorized into four groups based on the quartiles for each air pollutant. Adjusted HR #, adjusted for age, sex, urbanization level, and comorbidities of alcohol abuse/dependence, tobacco abuse/dependence, chronic obstructive pulmonary disease, and asthma.
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Lai, P.-Y.; Lee, C.-Y.; Chang, K.-H.; Chang, Y.-K.; Hsu, Y.-C.; Chiu, I.-M.; Tsai, S.C.-S.; Cho, D.-Y.; Lin, C.-L.; Lin, T.-H.; et al. The Risk of Developing Tinnitus and Air Pollution Exposure. Atmosphere 2025, 16, 618. https://doi.org/10.3390/atmos16050618

AMA Style

Lai P-Y, Lee C-Y, Chang K-H, Chang Y-K, Hsu Y-C, Chiu I-M, Tsai SC-S, Cho D-Y, Lin C-L, Lin T-H, et al. The Risk of Developing Tinnitus and Air Pollution Exposure. Atmosphere. 2025; 16(5):618. https://doi.org/10.3390/atmos16050618

Chicago/Turabian Style

Lai, Po-Yu, Chang-Yin Lee, Kuang-Hsi Chang, Yu-Kang Chang, Yi-Chao Hsu, Ing-Ming Chiu, Stella Chin-Shaw Tsai, Der-Yang Cho, Cheng-Li Lin, Tsung-Hsing Lin, and et al. 2025. "The Risk of Developing Tinnitus and Air Pollution Exposure" Atmosphere 16, no. 5: 618. https://doi.org/10.3390/atmos16050618

APA Style

Lai, P.-Y., Lee, C.-Y., Chang, K.-H., Chang, Y.-K., Hsu, Y.-C., Chiu, I.-M., Tsai, S. C.-S., Cho, D.-Y., Lin, C.-L., Lin, T.-H., & Chuang, W.-L. (2025). The Risk of Developing Tinnitus and Air Pollution Exposure. Atmosphere, 16(5), 618. https://doi.org/10.3390/atmos16050618

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