1. EHS 655 Lecture 2: Introduction and overview, continued

2. Setting the stage
So, what exposure will we be focusing on this semester?
Exposure selected based on…
Ubiquity of exposure (e.g., many sources)
Variability of exposure
Range of health effects
Availability of dataset
Over-emphasis on chemicals at SPH

3. Setting the stage
Will use dataset of noise exposures and two health outcomes related to noise
Hearing loss
Hypertension
Concepts from this analysis can be readily applied to
Any hazard
Workplace and community exposures

4. Noise and associated health effects
Noise among most common occupational exposures
Noise-induced hearing loss (NIHL) among most common, well-understood occupational diseases
100% preventable, but permanent, irreversible
Profound social and occupational effects
Linked to injuries and non-auditory effects
Time course of NIHL from variable noise unclear
Non-auditory effects of noise less well-understood
Hypertension, ischemic heart disease, etc
NIOSH, 1998; Berger, Royster, Royster, Driscoll, Layne, 2000

5. Noise and hearing loss
Henderson D et al, Ear Hear 2006

6. Noise and hearing loss
Henderson D et al, Ear Hear 2006

7. Noise and hearing loss

8. Noise and hearing loss

9. Noise and CVD
Van Kempen et al, Environ Health Persp, 2002

10. Environmental noise and CVD
Meta-analysis, 7-17% increase in CVD per 10 dB increase
Basner et al, Lancet, 2014

11. Environmental noise and CVD
World Health Organization: >1 million healthy life years (i.e., Disability-Adjusted Life Years, DALYs) lost annually due to environmental noise (Note: does not consider occupational noise)
Basner et al, Lancet, 2014

12. Environmental noise and CVD
Estimated US CVD savings from 5 dB reduction in population noise in 2014: $3.9 billion
Swinburn et al, Am J Prev Med, 2015

13. Occup. noise and CVD
Retrospective cohort, 27,464 workers, mean 92 dBA, 24 years avg f/u
Davies et al, Epidemiol, 2005

14. One way to assess CVD: blood pressure
Measured using 2 numbers (e.g., 120 over 80 or 120/80)
First number = systolic blood pressure
Measures the pressure in blood vessels when heart beats
Second number = diastolic blood pressure
Measures pressure in blood vessels when heart rests between beats

15. Okay, so noise is bad. Why do we need another study?
Anyone know Hill’s Criteria for Causality?

16. NIHL claims in one industry with highly variable noise
7.5% workforce , 21% accepted NIHL claims
1998 cost: $57 mil
All Industries
Daniell, Fulton-Kehoe, Cohen, Swan, Franklin, 2002

17. Overview of study (some of) our data come from
Prospective study of early NIHL among construction workers,
Why are studies like this rare?
Workers recruited at start of apprenticeship programs
Annual subject visit to University of Washington, Seattle with:
Extensive battery of hearing tests
Survey of work experience, tasks, perceptions of exposure
Direct exposure measurements on cohort infeasible

18. Blood pressure data from study
Did not actually collect blood pressure data
I have simulated data and added it to dataset provided
Everything else in the dataset is real

19. Data needed to understand risk of health effects of noise
Frequency
Duration
Intensity
Variability
Personal risk factors
Protective behaviors
Dose
Frequency x Duration x Intensity = Exposure

20. Exposure assessment in construction

21. Exposure assessment Full-shift dosimetry measurements
Convenience sample of construction workers at sites around Puget Sound
Shifts not all exactly 8 hours
Dosimeters datalog exposure parameters at 1-min intervals
Average level (LEQ)
Maximum level (LMAX)
Workers simultaneously record tasks, hearing protector use, etc.

22. Task-based exposure assessment

23. Subjective rating (SR) of noise exposure
Workers assess own noise exposure via SR
Simultaneously measure noise exposure
Combine for quantitative exposure estimate
Neitzel, Daniell, Sheppard, Davies, Seixas, 2009

24. Data needed to understand risk of health effects of noise
Frequency
Duration
Intensity
Variability
Personal risk factors
Protective behaviors
Dose

25. Variability – alternative metrics
Different exposure parameters may help explain health effects
Average
Maximum or peak
Can also compute ratios of these parameters
Maximum/average (peakiness of levels)
Seixas, Sheppard, Neitzel, 2005; Rappaport, 1991

26. Data needed to understand risk of health effects of noise
Frequency
Duration
Intensity
Variability
Personal risk factors
Protective behaviors
Dose

27. Non-occupational sources of noise in life
Others? 27

28. Data needed to understand risk of health effects of noise
Frequency
Duration
Intensity
Variability
Personal risk factors
Protective behaviors
Dose

29. Factors to consider regarding use of hearing protectors
Is it used and is it effective?

30. Other protective “behaviors”
Acoustic reflex
Biomarker of exposure and susceptibility
Temporary Threshold Shift at 2 mins post-exposure, TTS2

31. Data needed to understand risk of health effects of noise
Frequency
Duration
Intensity
Variability
Personal risk factors
Protective behaviors
Dose

32. From the reading
Kauppinen 1991, Appl Occup Environ Hyg

33. Introduction to the data files
Types of files
Dataset files
Variable description files
You’ll be using and referring to both regularly
How they’ll be introduced
New version of dataset most weeks, with additional variables and (at least once) more measurements

34. Introduction to Stata The program The do-file Why use a do-file?
Ease of manipulation of data
Documentation of manipulations and analyses
Preserve original data file
I’m forcing you to

35. Resources
Statistics Consulting Group, University of California-Los Angeles Institute for Digital Research and Education
Which statistical analysis should I use?
Stata online help files
Frequently asked questions on using Stata