Mortality of Deep Brain Stimulation and Risk Factors in Patients With Parkinson's Disease: A National Cohort Study in Korea

Background@#This study aimed to investigate 1) long-term outcomes of deep brain stimulation (DBS), such as mortality after DBS as well as the causes of death, 2) demographic and socioeconomic factors influencing mortality, and 3) comorbidities affecting mortality after DBS in patients with Parkinson’s disease (PD). @*Methods@#This study analyzed the National Health Insurance Service-National Health Information Database. Data on patients with PD diagnosis codes from 2002 to 2019 were extracted and analyzed. Data on the causes of death were obtained by linking the causes of death to data from Statistics Korea. The Kaplan-Meier method with the log-rank test was used for survival analysis. Multivariate Cox regression analyses were used to estimate hazard ratios (HRs) and their 95% confidence intervals. Regarding comorbidities such as PD dementia and fracture, which did not satisfy the assumption for the proportional HR, timedependent Cox analysis with the Mantel-Byar method was used. @*Results@#From 2005 to 2017, among 156,875 patients diagnosed with PD in Korea, 1,079 patients underwent DBS surgery, and 251 (23.3%) had died by 2019. The most common cause of death (47.1%) was PD. In the multivariate Cox regression analysis, the higher the age at diagnosis and surgery, the higher the mortality rate. The men and medical aid groups had significantly higher mortality rates. PD dementia and fracture were identified as risk factors for mortality. @*Conclusion@#Older age at diagnosis and surgery, being male, the use of medical aid, and the comorbidity of dementia and fractures were associated with a higher risk of mortality after DBS in patients with PD. Neurologists should consider these risk factors in assessing the prognosis of PD patients undergoing DBS.

Innate Type 2 Response to Aspergillus fumigatus in a Murine Model of Atopic Dermatitis–like Skin Inflammation

Background@#Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease mediated by T helper type 2 (Th2) cells in acute phase. Group 2 innate lymphoid cells (ILCs) play a role in the initiation of the Th2 response. Although mold exposure is associated with the development of AD, studies on the underlying mechanisms are lacking. This study investigated whether group 2 ILCs are involved in inflammation in AD-like skin induced by Aspergillus fumigatus (Af). @*Methods@#We investigated changes of group 2 ILCs population in Af-induced AD-like skin lesions. To induce AD-like skin lesions, Af extracts were applied to the dorsal skin of BALB/c and Rag1−/− mice five times per week, with repeat exposures at 2-week intervals. @*Results@#The clinical parameters were higher in the Af-treated group than in the control group. Histologic findings revealed epiderrmal and dermal thickening as well as eosinophil and mast cell infiltration into the skin of Af-treated mice. Populations of group 2 ILCs in the skin were also significantly higher in the Af-treated group. In addition, interleukin-33 mRNA expression was significantly higher in the skin lesions of the Af-treated mice. In the Rag1−/− mice lacking mature lymphocytes, AD-like skin lesions were still induced by Af and ILCs depletion using an anti-CD90.2 mAb lowered the Af-induced inflammatory response. @*Conclusions@#Group 2 ILCs may play a role in a murine model of Af-induced AD-like skin lesions.

Innate Type 2 Response to Aspergillus fumigatus in a Murine Model of Atopic Dermatitis–like Skin Inflammation

Background@#Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease mediated by T helper type 2 (Th2) cells in acute phase. Group 2 innate lymphoid cells (ILCs) play a role in the initiation of the Th2 response. Although mold exposure is associated with the development of AD, studies on the underlying mechanisms are lacking. This study investigated whether group 2 ILCs are involved in inflammation in AD-like skin induced by Aspergillus fumigatus (Af). @*Methods@#We investigated changes of group 2 ILCs population in Af-induced AD-like skin lesions. To induce AD-like skin lesions, Af extracts were applied to the dorsal skin of BALB/c and Rag1−/− mice five times per week, with repeat exposures at 2-week intervals. @*Results@#The clinical parameters were higher in the Af-treated group than in the control group. Histologic findings revealed epiderrmal and dermal thickening as well as eosinophil and mast cell infiltration into the skin of Af-treated mice. Populations of group 2 ILCs in the skin were also significantly higher in the Af-treated group. In addition, interleukin-33 mRNA expression was significantly higher in the skin lesions of the Af-treated mice. In the Rag1−/− mice lacking mature lymphocytes, AD-like skin lesions were still induced by Af and ILCs depletion using an anti-CD90.2 mAb lowered the Af-induced inflammatory response. @*Conclusions@#Group 2 ILCs may play a role in a murine model of Af-induced AD-like skin lesions.

Effect of Weight Changes on the Development of Erosive Esophagitis / 가정의학회지

Background@#Gastroesophageal reflux disease is highly prevalent among overweight and obese individuals. This study aimed to investigate the effect of weight change on the development of erosive esophagitis (EE). @*Methods@#A retrospective review of medical records from a university hospital in South Korea identified 7,123 subjects who underwent routine health checkups in 2012 and 2014. We excluded participants with EE in 2012. Body mass index (BMI) changes were classified as loss, stable, mild gain, or moderate gain. @*Results@#Mild and moderate weight gain increased the odds of EE development (odds ratio [OR], 1.39; 95% confidence interval [CI], 1.06–1.84 and OR, 2.80; 95% CI, 1.87–4.21, respectively) relative to weight stability. Weight loss decreased the odds of EE development (OR, 0.58; 95% CI, 0.38–0.90) relative to weight stability. After stratifying subjects into three groups by baseline BMI, those with mild and moderate weight gain in the obese group and moderate gain in the overweight group showed increased odds of EE development relative to members of those groups whose weights remained stable (OR, 2.08; 95% CI, 1.29–3.36; OR, 3.92; 95% CI, 1.99–7.73 in obese group, and OR, 3.30; 95% CI, 1.64–6.64 in overweight group, respectively). In comparison, weight loss in the normal weight group decreased the odds of EE development relative to weight stability (OR, 0.38; 95% CI, 0.15–0.97). @*Conclusion@#Weight gain was positively associated with EE development in overweight or obese individuals. Weight loss was negatively associated with EE development in normal-weight individuals.

The Prevalence and Incidence of Insomnia in Korea during 2005 to 2013

Objective@#The aim of this study was to estimate the progress of insomnia prevalence and incidence over the past several years. Also, this study compared survival rates between individuals with and without insomnia. @*Methods@#The National Health Insurance Service-National Sample Cohort (NHIS-NSC) from 2002–2013 was used for this study. Prevalent cases of insomnia were defined using ICD-10 codes F51.0 or G47.0, or a prescription of sedatives. Cox’s proportional hazard analysis was conducted to compare survival rates between insomnia patients and people without insomnia. @*Results@#In 2013, there were 46,167 (5.78%) insomnia patients over 20 years old in this cohort. Insomnia was more common among women and the elderly. Annual incidence over the past several years remained steady but the prevalence increased. The survival of insomnia patients was lower than that of people without insomnia, and the hazard ratio for overall mortality was 1.702 (p<0.001). @*Conclusion@#This large-scale population-based cohort study provided current epidemiologic indicators of insomnia in the Korean general population.

The effect of diabetes on 4-year changes of hearing thresholds in male workers exposed to noise in a single company: a longitudinal study

BACKGROUND: Recently, several studies have assessed the association between diabetes and hearing impairment. However, the effect of diabetes on hearing impairment is not well known in diabetic patients exposed to noise, a typical cause of hearing impairment. The aim of this study is to longitudinally analyze the effect of diabetes on hearing impairment in workers exposed to similar noise levels from 2013 to 2017 who had experienced little change in their working conditions. METHODS: The study subjects included 2,087 male workers exposed to noise in a single company and who underwent health examinations at the same hospital in Ulsan city in 2013 and 2017. Hearing impairment was defined that a pure-tone average of pure-tone audiometry (PTA) thresholds at 1,000, 2,000, 3,000, and 4,000 Hz was 25 dB and over in both ears. Statistical analyses were conducted using χ2 tests, ANOVA, and Cox proportional hazard models. We analyzed covariates that might affect hearing impairment, including age; working period; levels of total cholesterol, triglyceride, and serum creatinine; smoking and alcohol history; and noise level. RESULTS: The average PTA thresholds and their average changes between 2013 and 2017 were significant in the diabetes mellitus (DM) group than those in the normal and impaired fasting glucose group. Among the subjects with the same status of fasting glucose group in 2013 and 2017, the adjusted hazard ratios for incident hearing impairment among those in the DM group compared to normal group were 3.35 (95% confidence interval [CI], 1.54–7.29) in the left ear and 5.66 (95% CI, 2.01–15.98) in the right ear. CONCLUSIONS: This study suggested that the risk of hearing impairment in the DM group was significantly higher than that in the normal group in both ears, even when exposed to similar noise levels.

Simultaneous Analysis of Four Standards of The Herbal Formula, DF-02, of Ephedra intermedia and Rheum palmatum, using by High Performance Liquid Chromatography-Ultraviolet Detector (HPLC-UVD)

The herbal formula, DF-02, consisting of Ephedra intermedia and Rheum palmatum are used for the treatment of the metabolic diseases such as obesity and liver fibrosis in Korean local clinics. We aimed to develop the simultaneous analytical conditions for four standards, (+)-pseudoephedrine (PSEP) and (−)-ephedrine (EP) for E. intermedia, and aloe-emodin (AE) and chrysophanol (CP) for R. palmatum using HPLC-UV techniques. The validated conditions yielded the high precision (relative standard deviation (RSD) 0.9994). As a result, four standards of DF-02 were simultaneously determined under the developed method, which will be utilized for the quality control or evaluation of DF-02 and many herbal preparations containing E. intermedia and R. palmatum.

Low Income as a Vulnerable Factor to the Effect of Noise on Insomnia

OBJECTIVE: The present study aimed to examine the potential mediating effect of income level on the association between noise exposure and insomnia. METHODS: 706 individuals were evaluated in conjunction with 2014 noise map data from Seoul, South Korea. Cross-sectional analysis was performed to examine differences in noise level according to household income, while three separate logistic regression models were used to examine factors influencing insomnia. Odds ratios (ORs) were calculated after adjusting for depression, anxiety, auditory acuity and noise sensitivity in the first model. Analyses were adjusted for sociodemographic variables in the second model, lifestyle factors and medical illnesses in the third model. RESULTS: Noise level was significantly associated with an increased risk of insomnia in the low-income group, although no such association was observed in the high-income group. Groups exposed to >60 dB of noise (Lden; day-evening-night equivalent) exhibited a 1.79-fold increase in the incidence of insomnia relative to those exposed to <50 dB. The result was significant after adjusting sociodemographic variables, although not significant when adjusted for lifestyle factors and medical illnesses. CONCLUSION: Individuals with low income may be more vulnerable to the deleterious effects of noise exposure on health. Various aspects including income should be considered to ascertain the influence of noise on insomnia.

Comparing Attention and Cognitive Function in School Children across Noise Conditions: A Quasi-Experimental Study

OBJECTIVE: The effect of acute noise on cognitive function has long been a topic of study, yet these effects remain a serious problem for learning performance in school children. METHODS: From November 15, 2010 to December 8, 2010, we enrolled 268 students from three elementary schools (135 boys and 133 girls, 10–12 years old) in Ulsan, Korea. The study subjects were divided into two groups according to their test conditions (background versus additional noise), and tests were conducted using psychological examination tools. Chi-square tests and general linear models were used to assess the differences of impacts on cognition between the two groups. RESULTS: After adjusting for socio-demographic covariates, the noise significantly affected the results of full-scale IQ, verbal IQ, Continuous Performance Test scores, and Children’s Color Trails Test and Stroop test scores. The groups at high risk of learning difficulties were more affected by noise than low-risk groups. CONCLUSION: These findings suggest that noise is hazardous to the attention and performance of elementary school students, particularly for groups at greater risk for poor academic achievement. Additional studies are needed to identify subject-specific levels of noise that can affect attention and cognitive function.

Environmental and Body Concentrations of Heavy Metals at Sites Near and Distant from Industrial Complexes in Ulsan, Korea

BACKGROUND: Industrial pollution may affect the heavy metal body burden of people living near industrial complexes. We determined the average concentrations of atmospheric heavy metals in areas close to and distant from industrial complexes in Korea, and the body concentrations of these heavy metals in residents living near and distant from these facilities. METHODS: The atmospheric data of heavy metals (lead and cadmium) were from the Regional Air Monitoring Network in Ulsan. We recruited 1,148 participants, 872 who lived near an industrial complex (“exposed” group) and 276 who lived distant from industrial complexes (“non-exposed” group), and measured their concentrations of blood lead, urinary cadmium, and urinary total mercury. RESULTS: The results showed that atmospheric and human concentrations of heavy metals were higher in areas near industrial complexes. In addition, residents living near industrial complexes had higher individual and combined concentrations (cadmium + lead + mercury) of heavy metals. CONCLUSION: We conclude that residents living near industrial complexes are exposed to high concentrations of heavy metals, and should be carefully monitored.

Perceptions regarding utilization of meteorological information in healthcare in Korea: a qualitative study

BACKGROUND: Health forecasting has been used in an attempt to provide timely and tailored meteorological information to patients and healthcare providers so that they might take appropriate actions to mitigate health risks and manage healthcare-related needs. This study examined the in-depth perceptions of healthcare providers and the general public regarding the utilization of meteorological information in the healthcare system in Korea. METHODS: The COREQ (Consolidated Criteria for Reporting Qualitative Research) checklist was applied to this study. We conducted three focus group discussions in accordance with semi-structured guidelines developed to deal with various aspects of the utilization of meteorological information in healthcare settings. The verbatim transcriptions and field notes were analyzed according to content analysis. RESULTS: Six physicians, four nurses, three emergency medical technicians, and seven members of the general public participated in the focus group discussions. There were some individual discrepancies among most participants regarding the health effects of climate change. Although several physician participants felt that meteorological information utilization is not a prime concern during patient care, most of the general public participants believed that it should be used in the patient care process. The provision of meteorological information to patients undergoing care is expected to not only improve the effective management of climate-sensitive diseases, but also boost rapport between healthcare providers and patients. CONCLUSIONS: More attempts should be made to provide meteorological information to groups vulnerable to climate change, and the effects of this information should be evaluated in terms of effectiveness and inequality. The findings of this study will be helpful in countries and institutions trying to introduce health forecasting services. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s40557-018-0214-3) contains supplementary material, which is available to authorized users.

Correction to: Perceptions regarding utilization of meteorological information in healthcare in Korea: a qualitative study

The authors flagged that the Funding information in the Declarations was incorrect.

Effect of shift work on hypertension: cross sectional study

BACKGROUND: The need of efficient resource management and full-time accessibility to resources has increased with the development of industry, resulting in the increase of shift workers. Previous researches of past decades show that there are various health effects on shift workers. However, the definition and the form of shift work have varied from each research and occupational harmful factors except for shift work have not been excluded completely in previous researches. Therefore, in this research, we tried to find out the effect of shift work focusing on the hypertension. To complement previously mentioned weakness of other researches, we performed our research on participants to whom we could minimize other risk factors excluding shift work. METHODS: This research examined 1,953 petrochemical plant male workers (shift work 1,075, day worker 878) who did medical checkup from 1st Jan. 2014 to 31th Dec. 2014 in a general hospital located in Ulsan, based on their medical records and questionnaires. With the questionnaire, we found out their basic information including age, social status, occupational history, and we took their physical measurements. RESULTS: Compared to day workers, shift workers' odds ratio of developing hypertension was 1.31 (95% CI 0.98–1.75). After adjusting confounding variables, adjusted odds ratio for entire subjects was 1.51 (95% CI 1.11–2.06). Also, for subjects who were in continuous service for over 20 years, odds ratio was 1.51 (95% CI 1.08–2.11). CONCLUSIONS: Shift workers had a higher chance of hypertension than day workers do. Particularly, the longer the workers work continuously, the risk of hypertension getting higher.

The responses of subjective feeling, task performance ability, cortisol and HRV for the various types of floor impact sound: a pilot study

BACKGROUND: Recently, noise coming from the neighborhood via floor wall has become a great social problem. The noise between the floors can be a cause of physical and psychological problems, and the different types of floor impact sound (FIS) may have the different effects on the human's body and mind. The purpose of this study is to assess the responses of subjective feeling, task performance ability, cortisol and HRV for the various types of floor impact. METHODS: Ten men and 5 women were enrolled in our study, and the English listening test was performed under the twelve different types of FIS, which were made by the combinations of bang machine (B), tapping machine (T), impact ball (I) and sound-proof mattress (M). The 15 subjects were exposed to each FIS for about 3 min, and the subjective annoyance, performance ability (English listening test), cortisol level of urine/saliva and heart rate variability (HRV) were examined. The sound pressure level (SPL) and frequency of FIS were analyzed. Repeated-measures ANOVA, paired t-test, Wilcoxon signed rank test were performed for data analysis. RESULTS: The SPL of tapping machine (T) was reduced with the soundproof mattress (M) by 3.9–7.3 dBA. Impact ball (I) was higher than other FIS in low frequency (31.5–125 Hz) by 10 dBA, and tapping machine (T) was higher than other FIS in high frequency (2–4 k Hz) by 10 dBA. The subjective annoyance is highest in the combination of bang machine and tapping machine (BT), and next in the tapping machine (T). The English listening score was also lowest in the BT, and next in T. The difference of salivary cortisol levels between various types of FIS was significant (p = 0.003). The change of HRV parameters by the change of FIS types was significant in some parameters, which were total power (TP) (p = 0.004), low frequency (LF) (p = 0.002) and high frequency (HF) (p = 0.011). CONCLUSIONS: These results suggest that the human's subjective and objective responses were different according to FIS types and those combinations.

The association between cadmium and lead exposure and blood pressure among workers of a smelting industry: a cross-sectional study

BACKGROUND: Lead and cadmium are harmful heavy metals that are used for a variety of occupational purposes. Considering their potentially hazardous effects on health, studies on the association between exposure to these two heavy metals and health disorders have been actively conducted. This study aimed to determine the association between blood lead and cadmium levels and blood pressure in workers exposed to lead and cadmium in a smelter. METHODS: Nine hundred and sixty-three male workers who worked in a smelter, and underwent medical examinations at the Ulsan University Hospital between January 1 and December 31, 2014, were selected as participants. Among them, 310 subjects whose data on height, weight, blood pressure, fasting blood glucose, lipid profile, and blood lead and cadmium levels were available and who answered the questionnaire were selected as the final participants. We investigated the drinking habit, smoking status, exercise adequacy, and family history of hypertension of these workers using formal questionnaires. A statistical analysis was conducted using Student's t-test, analysis of variance, and linear or logistic regression. RESULTS: The association between blood lead and cadmium levels and blood pressure was analyzed through statistical adjustment of the risk factors of hypertension. Results showed an association between blood cadmium level and blood pressure elevation. However, blood lead level was found to be not correlated with blood pressure elevation. CONCLUSIONS: This study shows the association between blood cadmium level and systolic blood pressure (SBP) and diastolic blood pressure (DBP) elevation. TRIAL REGISTRATION: IRB No. 2017–03-037. Retrospectively Registered 30 March 2017.

Comparisons of hearing threshold changes in male workers with unilateral conductive hearing loss exposed to workplace noise: a retrospective cohort study for 8 years

BACKGROUND: The purpose of this study was to investigate hearing threshold changes of workers with unilateral conductive hearing loss who were exposed to workplace noise for 8-years. METHODS: Among 1819 workers at a shipyard in Ulsan, 78 subjects with an air-bone gap ≥10 dBHL in unilateral ears were selected. Factors that could affect hearing were acquired from questionnaires, physical examinations, and biochemistry examinations. Paired t-test was conducted to compare the hearing threshold changes over time between conductive hearing loss (CHL) ear and sensorineural hearing loss (SNHL) ear. RESULTS: The study included male subjects aged 48.7 ± 2.9, having worked for 29.8 ± 2.7 years. Hearing thresholds increased significantly in CHL ears and SNHL ears at all frequencies (0.5–6 kHz) during follow-up period (p < 0.05). The threshold change at 4 kHz was 3.2 dBHL higher in SNHL ears which was statistically significant (p < 0.05). When workers were exposed to noise levels of 85 dBA and above, threshold change at 4 kHz was 5.6 dBHL higher in SNHL ears which was statistically significant (p < 0.05). Among workers aged below 50, the threshold change values were lower in low-frequency (0.5–2 kHz) in SNHL ears, with a small range of changes, whereas in high-frequency (3–6 kHz), the range of changes was greater SNHL ears (p < 0.05). Among workers aged 50 and above, SNHL ears showed a wider range of changes in both high- and low-frequency areas (p < 0.05). CONCLUSIONS: At high-frequencies, particularly at 4 kHz, the range of hearing threshold changes was lower in ears with conductive hearing loss than in contralateral ears. This is suggested as a protective effect against noise exposure.

The Effects of Different Noise Types on Heart Rate Variability in Men

PURPOSE: To determine the impact of noise on heart rate variability (HRV) in men, with a focus on the noise type rather than on noise intensity. MATERIALS AND METHODS: Forty college-going male volunteers were enrolled in this study and were randomly divided into four groups according to the type of noise they were exposed to: background, traffic, speech, or mixed (traffic and speech) noise. All groups except the background group (35 dB) were exposed to 45 dB sound pressure levels. We collected data on age, smoking status, alcohol consumption, and disease status from responses to self-reported questionnaires and medical examinations. We also measured HRV parameters and blood pressure levels before and after exposure to noise. The HRV parameters were evaluated while patients remained seated for 5 minutes, and frequency and time domain analyses were then performed. RESULTS: After noise exposure, only the speech noise group showed a reduced low frequency (LF) value, reflecting the activity of both the sympathetic and parasympathetic nervous systems. The low-to-high frequency (LF/HF) ratio, which reflected the activity of the autonomic nervous system (ANS), became more stable, decreasing from 5.21 to 1.37; however, this change was not statistically significant. CONCLUSION: These results indicate that 45 dB(A) of noise, 10 dB(A) higher than background noise, affects the ANS. Additionally, the impact on HRV activity might differ according to the noise quality. Further studies will be required to ascertain the role of noise type.

Update on Management of Compressive Neuropathy: Tarsal Tunnel Syndrome / 대한정형외과학회잡지

The tarsal tunnel is located beneath the flexor retinaculum, which connects the medial malleolus and calacaneus. The tarsal tunnel contains the posterior tibialis tendon, flexor digitorum longus tendon, posterior tibial artery and vein, posterior tibial nerve, and flexor halluces longus tendon. Tarsal tunnel syndrome is a compressive neuropathy of posterior tibial nerve and its branches under the flexor retinaculum. The etiologies of tarsal tunnel syndrome are space-occupying lesion, hypertrophied flexor retinaculum, osteophytes, tarsal coalition, varicose vein, and trauma. The symptoms are foot pain and hypoesthesia or paresthesia at dermatome according to involving nerve branches. Clinical diagnosis can be obtained from a detailed history and physical examination such as compressive test at the tarsal tunnel area. Ultrasonography and magnetic resonance imaging can reveal the space-occupying lesion, such as ganglion, lipoma, and neuroma. The initial treatments of tarsal tunnel syndrome are conservative management, such as physical therapy, night splint, and steroid injection. Surgical decompression is indicated after failure of conservative managements. Variable results of surgical treatment have been reported. Favorable result after decompression could be obtained from young patients, early onset symptoms, and space-occupying lesion.

Physical Agents and Occupational Disease Compensation: Noise, Vibration, Radiation, and Other Physical Agents

The context of specific criteria for the recognition of occupational diseases (ODs) due to physical agents in the Enforcement Decree of the Industrial Accident Compensation Insurance Act (ED-IACIA) and the Labor Standard Act (LSA) does not describe definite disease along with the agents but listed symptoms or obscure clinical conditions. Moreover, the needs for an amendment of these Acts have recently attracted renewed interest. To establish agreed criteria for compensable ODs due to physical agents, we reviewed the criteria for recognizing ODs on the basis of International Labor Organization (ILO) documents and European Union (EU) guideline. After providing a brief review of the history of OD outbreaks due to physical exposure in South Korea and the responses to them, we describe the basis for the recent amendments to the IACI Act and LSA and assess their appropriateness. On the basis of these findings, this study could be helpful for determining and compensating process of ODs. However, further work is required to ascertain the scientific relationship between diseases caused by physical agents and the exposure criteria.

Relationship of cigarette smoking and hearing loss in workers exposed to occupational noise

OBJECTIVES: To investigate the effects of smoking on hearing loss among workers exposed to occupational noise. METHODS: From the results of a special workers health examination performed in 2011, we enrolled 8,543 subjects exposed to occupational noise and reviewed the findings. Using self-reported questionnaires and health examination results, we collected data on age, smoking status, disease status, height, weight, and biochemistry and pure tone audiometry findings. We divided the workers into 3 groups according to smoking status (non-smoker, ex-smoker, current smoker). Current smokers (n = 3,593) were divided into 4 groups according to smoking amount (0.05-9.9, 10-19.9, 20-29.9, > or =30 pack-years). We analyzed the data to compare hearing thresholds between smoking statuses using analysis of covariance (ANCOVA) after controlling for confounder effects. RESULTS: According to ANCOVA, the hearing thresholds of current smokers at 2 k, 3 k, and 4 kHz were significantly higher than that of the other groups. Multiple logistic regression for smoking status (reference: non-smokers) showed that the adjusted odds ratios of current smokers were 1.291 (95% confidence interval [CI]: 1.055-1.580), 1.180 (95% CI: 1.007-1.383), 1.295 (95% CI: 1.125-1.491), and 1.321 (95% CI: 1.157-1.507) at 1 k, 2 k, 3 k, and 4 kHz, respectively. Based on smoking amount, the adjusted odds ratios were 1.562 (95% CI: 1.013-2.408) and 1.643 (95% CI: 1.023-2.640) for the 10-19.9 and > or =30 pack-years group, respectively, at 1 kHz (reference: 0.05-9.9 pack-years). At 2 kHz, the adjusted odds ratios were increased statistically significantly with smoking amount for all groups. At all frequencies tested, the hearing thresholds of noise-exposed workers were significantly influenced by current smoking, in particular, the increase of hearing loss at low frequencies according to smoking amount was more prevalent. CONCLUSIONS: Current smoking significantly influenced hearing loss at all frequencies in workers exposed to occupational noise, and heavier smoking influenced low-frequency hearing loss more greatly. There was a dose-response relationship between smoking amount and low-frequency hearing thresholds; however, this was not observed for high-frequency hearing thresholds. Therefore, well-designed prospective studies are needed to clarify the effects of smoking on the degree of hearing loss.