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EHS 655 Lecture 2: Introduction and overview, continued 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 2 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 3 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 4 Noise and hearing loss Henderson D et al, Ear Hear 2006 5 Noise and hearing loss Henderson D et al, Ear Hear 2006 6 Noise and hearing loss 7 Noise and hearing loss 8 Noise and CVD Van Kempen et al, Environ Health Persp, 2002 9 Environmental noise and CVD Meta-analysis, 7-17% increase in CVD per 10 dB increase Basner et al, Lancet, 2014 10 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 11 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 12 Occup. noise and CVD Retrospective cohort, 27,464 workers, mean 92 dBA, 24 years avg f/u Davies et al, Epidemiol, 2005 13 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 https://www.cdc.gov/bloodpressure/measure.htm 14 Okay, so noise is bad. Why do we need another study? Anyone know Hill’s Criteria for Causality? http://nfs.unipv.it/nfs/minf/dispense/patgen/lectures/files/disease_causality.html 15 NIHL claims in one industry with highly variable noise 7.5% 6000 workforce 1984-96, 21% accepted NIHL claims Number of claims 5000 4000 1998 cost: $57 mil All other industries All Industries 3000 Construction 2000 1000 0 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 Year claim was filed (1984-1998) Daniell, Fulton-Kehoe, Cohen, Swan, Franklin, 2002 16 Overview of study (some of) our data come from Prospective study of early NIHL among construction workers, 2000-2010 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 17 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 18 Data needed to understand risk of health effects of noise Frequency Protective behaviors Duration Dose Personal risk factors Intensity Variability Frequency x Duration x Intensity = Exposure 19 Exposure assessment in construction 20 Exposure assessment Full-shift dosimetry measurements Dosimeters datalog exposure parameters at 1-min intervals Convenience sample of construction workers at sites around Puget Sound Shifts not all exactly 8 hours Average level (LEQ) Maximum level (LMAX) Workers simultaneously record tasks, hearing protector use, etc. 21 Task-based exposure assessment 100.0 Task A Task B Task A Task C Task A Noise Level (dBA) 90.0 80.0 70.0 60.0 Measured Exposure 50.0 40.0 0 50 100 150 200 250 Time (Minutes) 22 Subjective rating (SR) of noise exposure Workers assess own noise exposure via SR What percent of time were you exposed to each of the following noise levels at work? _____% No louder than a normal speaking voice _____% As loud as a vacuum _____% As loud as a gas lawnmower _____% As loud as a chainsaw The total should add to about 100 percent. _____% As loud or louder than a siren Total = about 100% Simultaneously measure noise exposure Combine for quantitative exposure estimate Neitzel, Daniell, Sheppard, Davies, Seixas, 2009 23 Data needed to understand risk of health effects of noise Frequency Protective behaviors Duration Dose Personal risk factors Intensity Variability 24 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 25 Data needed to understand risk of health effects of noise Frequency Protective behaviors Duration Dose Personal risk factors Intensity Variability 26 Non-occupational sources of noise in life Others? 27 Data needed to understand risk of health effects of noise Frequency Protective behaviors Duration Dose Personal risk factors Intensity Variability 28 Factors to consider regarding use of hearing protectors Is it used and is it effective? 29 Other protective “behaviors” Acoustic reflex Biomarker of exposure and susceptibility Temporary Threshold Shift at 2 mins postexposure, TTS2 30 Data needed to understand risk of health effects of noise Frequency Protective behaviors Duration Dose Personal risk factors Intensity Variability 31 From the reading Kauppinen 1991, Appl Occup Environ Hyg 32 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 33 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 34 Resources Statistics Consulting Group, University of CaliforniaLos Angeles Institute for Digital Research and Education Which statistical analysis should I use? http://www.ats.ucla.edu/stat/mult_pkg/whatstat/ Stata online help files Frequently asked questions on using Stata http://www.stata.com/support/faqs/ 35