Hearing Loss
Conditions
Keywords
noise, hearing loss, temporary threshold shift
Brief summary
This study will examine whether oral intake of 1200mg N-Acetylcysteine/day will prevent temporary threshold shift in hearing among workers exposed to noise
Detailed description
Both genetic and environmental factors contribute to noise-induced hearing loss (NIHL). The cellular antioxidant system appears to protect cochlear hair cells from oxidative stress due to noise. Previous animal studies showed protective effects of anti-oxidant medicines against NIHL.The objective of this study is to test the hypothesis that preventive medication of antioxidation is related to susceptibility to NIHL. The 53 noise-exposed workers from steel industries in Taiwan will be recruited, and divided into N-Acetylcysteine (NAC)(Acetine, 1200mg/day) group and placebo one. The duration of medication is 2 weeks initially. After washout for 2 weeks, the kinds of medications in these 2 groups will be crossover and used for 2 weeks. Firstly, questionnaires interview about noise exposure, smoking, alcohol drinking, drug habit history and calculation of Body Mass Index (BMI) will be done. The following methods would be performed individually after medication. With detailed local examination with otoscope, these subjects receive hearing tests by pure-tone audiometry (PTA) and distortion product otoacoustic emissions (DPOAE) before and after their daily works. The possible confounding factors including background noise, solvent, heavy metals, carbon monoxide and temperature in the workplaces will be assessed. The amount of noise exposure is evaluated by personal dosimeter. Early morning, Blood samples will be collected. Deletion polymorphisms in the Glutathione S-transferase (GST)T1 and GSTM1 genes will be determined. Statistical analysis will be performed to evaluate the relation between intake of anti-oxidant medicine and noise-induced temporal threshold shift (TTS). The expected results of this study are to determine whether anti-oxidant supplements protect workers from noise-induced TTS. We anticipate that these human studies might help elucidate the relative importance of anti-oxidant enzymes as risk factors for NIHL.
Interventions
DRUGN-acetylcysteine (NAC)
600mg twice daily for 2 weeks
DRUGglucose
1 gm glucose capsule
Sponsors
Institute of Occupational Safety and Health, Taiwan
Municipal Hospital of Tainan, Taiwan
National Taiwan University Hospital
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
MALE
Age
25 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* workers in steel industry * known exposure to noise at work
Exclusion criteria
* ever diagnosed as having diabetes mellitus * fasting glucose of 120 or greater
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Temporary Threshold Shift Measurement by Pure Tone Audiometry (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift) | A total of four hearing assessments were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift | The hearing threshold level (HL) at high frequency (HF) by pure-tone audiometry (PTA) was defined as the average of HLs at 3k,4k,6kHz for each ear examined. A total of four hearing assessments by PTA were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift. The amount of temporary threshold change was calculated by subtracting the pre-shift hearing threshold from the post-shift hearing threshold at each frequency. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Temporary Threshold Changes Measurement by Distortion Product Otoacoustic Emissions (DPOAE) (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift) | A total of four hearing assessments were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift | Distortion product otoacoustic emissions (DPOAE) is an objective measure to assess the cochlear changes. DPOAE response threshold at high frequency (HF) was defined as the average of response levels (dB SPL) at 3k,4k,6kHz for each ear examined. A total of four hearing assessments by DPOAE were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift. The amount of DPOAE temporary threshold change was calculated by subtracting the pre-shift DPOAE response threshold from the post-shift DPOAE response threshold at each frequency. |
Countries
Taiwan
Participant flow
Recruitment details
Participants recruited between November 2007 and January 2008.
Pre-assignment details
A total of 60 workers voluntarily participated in this study. However, 6 workers had preexisting hearing loss of \>50 dBA at high frequency and 1 worker accidentally turned off the noise monitoring device. These 7 participants were excluded from the analysis. The 53 workers who satisfactorily completed the study.
Participants by arm
| Arm | Count |
|---|---|
| N-acetylcysteine (NAC) First, Then Placebo Formulation NAC (1200 mg/day, 14 days) (Actein, Synmosa Corp., Taiwan) in the first intervention period and Placebo (a tablet of identical taste and odor to the NAC agent) in the second intervention period (after washout period). | 25 |
| Placebo First, Then N-acetylcysteine (NAC) Placebo in the first intervention period and Formulation NAC in the second intervention period (after washout period). | 28 |
| Total | 53 |
Baseline characteristics
| Characteristic | Placebo First, Then N-acetylcysteine (NAC) | N-acetylcysteine (NAC) First, Then Placebo | Total |
|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0.0 Participants |
| Age, Categorical >=65 years | 0 Participants | 0 Participants | 0.0 Participants |
| Age, Categorical Between 18 and 65 years | 28 Participants | 25 Participants | 53.0 Participants |
| Age Continuous | 42.1 years STANDARD_DEVIATION 9.6 | 40.0 years STANDARD_DEVIATION 11.6 | 41.1 years STANDARD_DEVIATION 10.5 |
| Region of Enrollment Taiwan | 28 participants | 25 participants | 53.0 participants |
| Sex: Female, Male Female | 0 Participants | 0 Participants | 0.0 Participants |
| Sex: Female, Male Male | 28 Participants | 25 Participants | 53.0 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 0 / 53 | 0 / 53 |
| serious Total, serious adverse events | 0 / 53 | 0 / 53 |
Outcome results
Primary
Temporary Threshold Shift Measurement by Pure Tone Audiometry (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift)
The hearing threshold level (HL) at high frequency (HF) by pure-tone audiometry (PTA) was defined as the average of HLs at 3k,4k,6kHz for each ear examined. A total of four hearing assessments by PTA were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift. The amount of temporary threshold change was calculated by subtracting the pre-shift hearing threshold from the post-shift hearing threshold at each frequency.
Time frame: A total of four hearing assessments were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift
Population: Intent to treat analysis including only participants who had at least one post-baseline assessment.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| N-acetylcysteine (NAC) | Temporary Threshold Shift Measurement by Pure Tone Audiometry (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift) | 3.4 decibels | Standard Deviation 2.3 |
| Placebo | Temporary Threshold Shift Measurement by Pure Tone Audiometry (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift) | 2.7 decibels | Standard Deviation 2.1 |
p-value: <0.05ANOVA
Secondary
Temporary Threshold Changes Measurement by Distortion Product Otoacoustic Emissions (DPOAE) (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift)
Distortion product otoacoustic emissions (DPOAE) is an objective measure to assess the cochlear changes. DPOAE response threshold at high frequency (HF) was defined as the average of response levels (dB SPL) at 3k,4k,6kHz for each ear examined. A total of four hearing assessments by DPOAE were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift. The amount of DPOAE temporary threshold change was calculated by subtracting the pre-shift DPOAE response threshold from the post-shift DPOAE response threshold at each frequency.
Time frame: A total of four hearing assessments were completed for each formulation period on the 1st day pre- and post-shift, and the 14th day pre- and post-shift
Population: Intent to treat analysis including only participants who had all 4 post-baseline assessments (measurements at beginning of 1st and 2nd intervention periods and end of 1st and 2nd intervention periods).
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| N-acetylcysteine (NAC) | Temporary Threshold Changes Measurement by Distortion Product Otoacoustic Emissions (DPOAE) (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift) | -0.85 decibels (dB SPL) | Standard Deviation 1.1 |
| Placebo | Temporary Threshold Changes Measurement by Distortion Product Otoacoustic Emissions (DPOAE) (A Total of Four Hearing Assessments Were Completed for Each Formulation Period on the 1st Day Pre- and Post-shift, and the 14th Day Pre- and Post-shift) | -0.89 decibels (dB SPL) | Standard Deviation 0.9 |
p-value: <0.05ANOVA