Contribution of hearing conservation program components to the prevention of noise-induced hearing loss (NIHL) Nicholas Heyer -Battelle Thais C. Morata -NIOSH Lynne E. Pinkerton -NIOSH Hyoshin Kim -Battelle Steve Sinclair - UC Northridge - PowerPoint PPT Presentation
Contribution of hearing conservation program components to the prevention of noise-induced hearing loss (NIHL) Nicholas Heyer -Battelle Thais C. Morata -NIOSH Lynne E. Pinkerton -NIOSH Hyoshin Kim -Battelle Steve Sinclair - UC Northridge
Description:
The findings and conclusions in this presentation are those of the authors and do not necessarily represent the views of the National Institute for Occupational ... – PowerPoint PPT presentation
Title: Contribution of hearing conservation program components to the prevention of noise-induced hearing loss (NIHL) Nicholas Heyer -Battelle Thais C. Morata -NIOSH Lynne E. Pinkerton -NIOSH Hyoshin Kim -Battelle Steve Sinclair - UC Northridge
1 Contribution of hearing conservation program components to the prevention of noise-induced hearing loss (NIHL) Nicholas Heyer - Battelle Thais C. Morata - NIOSH Lynne E. Pinkerton - NIOSH Hyoshin Kim - Battelle Steve Sinclair - UC Northridge Scott E. Brueck - NIOSH Daniel Stancescu - NIOSH Mary Prince Panaccio - NIOSH Martha A. Waters - NIOSH Cherie F. Estill - NIOSH John R. Franks - NIOSH The findings and conclusions in this presentation are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. 2 Study Questions
Can HCP quality be judged by evaluating their component parts?
Can historical data be useful in conducting such evaluations?
2 3 The initial study (1998-2000)
Historic review of 3 plants
2 automotive plants
1 food processor
Covers period from 1970 through 1999
3 4 Four Primary Sources of Data
Historic noise exposure surveys
Historic audiometric test records
Employee work histories
Survey focus group information on history of hearing conservation programs
4 5 8-Hour TWA noise exposure
Assigned by Job Title
Used task-based noise surveys from 1990s
Multiple stage extrapolation to earlier jobs and job titles
5 6 Linking noise exposure and NIHL
Merged historical audiometric testing data with work histories (job titles)
Excellent match for food processor
Poor match for two automotive plants
More than half of all audiometric testing conducted prior to initial work history
Possibly due to migration of workers from other plants
6 7 Creating HCP component variables
History based on worker focus groups
Four historical HCP components created
use of hearing protective devices (HPD)
Audiometric testing frequency (calculated)
Frequency responsiveness of noise monitoring
Worker education (at shop meetings testing)
7 8 Concerns about the data
Noise Exposure Accuracy of TWAs
Multiple stage extrapolation limited data points
Audiometric Thresholds
Workplace audiograms known to be variable
Duration of exposure
Missing work histories loss of data
Quality measures for HCP components
Memory based few historical documents
8 9 Cumulative noise exposure
Leq cumulative measure of equivalent noise energy
3 dB increase in TWA doubles exposure
Does not accommodate uncertainty
Historical estimates of duration better than intensity
Test alternative measure
Duration of exposure within 5 dB strata
Weightings determined by the data
9 10 Audiometric threshold
Not addressing hearing per se
No need to define a threshold shift
No censorship of data
Use a sensitive yet robust measure
Use most sensitive frequencies
Incorporate bilateral measures
Average across multiple thresholds
Solution
Average at 3, 4 6 kHz across both ears
10 11 Missing work histories
Reduced data vs. data uncertainty
Do missing work histories migration between plants?
Guessing could introduce large errors considered too risk
Conclusion Exclude audiograms with missing work histories
11 12 HCP component measures
Used dichotomous variables for all component quality measures
Used better vs. worse categorization
Fortunately these varied by time and plant
Did not necessarily improve over time
The four components did not necessarily vary together
12 13 Unreliable Responders
Extreme cases of threshold improvement
Some clustering by facility and time
Remove person not audiogram
Average improvement of gt15 dB
From baseline audiogram
From immediately preceding audiogram
5 of subjects removed
13 14 14 Analyses 15 Time between consecutive audiograms Unit of Analysis? Time between Baseline current audiograms 15 16 Unit of Analysis
Time from Baseline (1st valid) Audiogram
Reasons
Better captures cumulative exposure
Less dependent on accuracy of time cut-points for HCP quality measures
Less dependent on latency of impact
16 17 Two models of cumulative noise exposure
Variables included
Intercept dummy variables for plant
Baseline (time0) hearing threshold average
Age at time of test (timet)
Leq Duration of employment
Results
Duration of employment better predictor of NIHL
Majority of noise exposures between 85-95 dB
17 18 Duration of Noise Exposure Stratified by TWA
Tested stratified model duration of exposure within 5 dB TWA groups
duration at gt95 dB
duration at lt95 dB
Baseline test 1 .test 2 .test 3 .. test n
Stratified duration for nth audiometric test period for this subject
Only strata significantly different from total exposure duration was for gt95 dB
18 19 Duration of Noise Exposure Stratified by TWA and years
Model duration of exposure by TWA and duration groups (over x years in red)
duration at 95 dB
duration at lt95 dB
Baseline test 1 .test 2 .test 3 .. test n
Two-way stratified duration for nth audiometric test period for this subject
Observed change in the dose-response relationship after 6 years
19 20 Adding terms for HCP quality
HCP quality term entered separately for each component
Duration in Worse quality HCP (red) does not add to term
Duration in Better quality HCP
Baseline test 1 .test 2 .test 3 .. test n
Duration in Better quality HCP for nth audiometric test period for this subject
Interaction terms yielded incoherent results
20 21 21 Results 22 NIHL model with/without HPD use
Base Model HPD Model
Variables Coeff Coeff
Intercept -1.89 -2.18
Plant X -1.02 0.62
Plant Y -0.39 -0.03
Reflecting Individual Characteristics
Baseline Threshold -0.03 -0.03
Age at Test 0.08 0.08
Reflecting NIHL
Duration at lt95dB / lt6 (years) 0.60 0.77
Duration at gt95dB / lt6 (years) 0.82 1.04
Duration at lt95dB / gt6 (years) 0.52 0.79
Duration at gt95dB / gt6 (years) 0.44 0.69
Better HPD Use (Years) ----- -0.31
Coefficients directly reflect average threshold change per variable unit
plt0.05 plt0.01 plt0.001 plt0.0001
22 23 Hearing Protective Devices
HPD programs effective in reducing NIHL
Reported enforcement of HPD policies
Did not use information on types of devices
No consensus on relative effectiveness of different devices
Dependent on use and acceptance of the various devices
23 24 NIHL model with/without quality audiometric monitoring
Base Model HPD Model
Variables Coeff Coeff
Intercept -1.89 -2.18
Plant X -1.02 0.85
Plant Y -0.39 -0.43
Reflecting Individual Characteristics
Baseline Threshold -0.03 -0.03
Age at Test 0.08 0.08
Reflecting NIHL
Duration at lt95dB / lt6 (years) 0.60 0.54
Duration at gt95dB / lt6 (years) 0.82 0.77
Duration at lt95dB / gt6 (years) 0.52 0.44
Duration at gt95dB / gt6 (years) 0.44 0.31
Better Audiometric Monitoring (Years) ----- 0.13
Coefficients directly reflect average threshold change per variable unit
plt0.05 plt0.01 plt0.001 plt0.0001
24 25 Audiometric Testing
Apparent reverse association (more testing, more threshold change detected)
Used mean time between tests
Need better descriptors
Possibly due to artifacts
People with poor hearing may resist initial testing
Longer term employees supervisors may resist testing
25 26 NIHL model with/without better noise monitoring
Base Model HPD Model
Variables Coeff Coeff
Intercept -1.89 -2.09
Plant X -1.02 0.48
Plant Y -0.39 -0.31
Reflecting Individual Characteristics
Baseline Threshold -0.03 -0.03
Age at Test 0.08 0.08
Reflecting NIHL
Duration at lt95dB / lt6 (years) 0.60 0.64
Duration at gt95dB / lt6 (years) 0.82 0.83
Duration at lt95dB / gt6 (years) 0.52 0.53
Duration at gt95dB / gt6 (years) 0.44 0.43
Better Noise Monitoring (Years) ----- -0.13
Coefficients directly reflect average threshold change per variable unit
plt0.05 plt0.01 plt0.001 plt0.0001
26 27 Noise Monitoring
Apparent effect - BUT
Noise Exposure coefficients basically same
Larger change in plant coefficient
No variation by time within plants
Only one plant had a better program
Conclusion Effect due to confounding
27 28 NIHL model with/without better worker training
Base Model HPD Model
Variables Coeff Coeff
Intercept -1.89 -1.87
Plant X -1.02 -0.99
Plant Y -0.39 -0.47
Reflecting Individual Characteristics
Baseline Threshold -0.03 -0.03
Age at Test 0.08 0.08
Reflecting NIHL
Duration at lt95dB / lt6 (years) 0.60 0.63
Duration at gt95dB / lt6 (years) 0.82 0.84
Duration at lt95dB / gt6 (years) 0.52 0.54
Duration at gt95dB / gt6 (years) 0.44 0.43
Better Worker Training (Years) ----- -0.04
Coefficients directly reflect average threshold change per variable unit
plt0.05 plt0.01 plt0.001 plt0.0001
28 29 Worker Training
Weak non-significant association
None of the programs were very satisfactory
Sporadic at best
Better could only be used as a relative term
Conclusion not enough variability
29 30 30 Conclusions 31 Usefulness of historic data
PowerShow.com is a leading presentation sharing website. It has millions of presentations already uploaded and available with 1,000s more being uploaded by its users every day. Whatever your area of interest, here you’ll be able to find and view presentations you’ll love and possibly download. And, best of all, it is completely free and easy to use.
You might even have a presentation you’d like to share with others. If so, just upload it to PowerShow.com. We’ll convert it to an HTML5 slideshow that includes all the media types you’ve already added: audio, video, music, pictures, animations and transition effects. Then you can share it with your target audience as well as PowerShow.com’s millions of monthly visitors. And, again, it’s all free.
About the Developers
PowerShow.com is brought to you by CrystalGraphics, the award-winning developer and market-leading publisher of rich-media enhancement products for presentations. Our product offerings include millions of PowerPoint templates, diagrams, animated 3D characters and more.