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NATIONAL HEALTH INTERVIEW SURVEY
OCCUPATIONAL HEALTH SUPPLEMENT

Methods for NORA Sector Profiles based on Key Findings from the 2010 National Health Interview Survey Occupational Health Supplement
(NHIS-OHS)

National Health Interview Survey

The data analyzed in the sector profiles come from the 2010 National Health Interview Survey (NHIS).  The NHIS is a cross-sectional in-person household survey conducted continuously since 1957 by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC).   Data are collected on the civilian noninstitutionalized population of the United States, and thus exclude persons in long-term care facilities (e.g., nursing homes) or correctional facilities, active-duty Armed Forces personnel (although civilian family members are included), and U.S. nationals living in foreign countries. The survey uses a multi-stage clustered sample design, with oversampling of black, Hispanic, and Asian persons, and produces nationally representative data on health insurance coverage, health care access and utilization, health status, health behaviors, and other health-related topics.

The NHIS questionnaire consists of a core set of questions that remain relatively unchanged from year to year, and supplemental questions that vary from year to year to collect additional data pertaining to current health issues of national importance.  The core survey instrument has four main modules: Household, Family, Sample Child, and Sample Adult.  The first two modules collect health and sociodemographic information on each member of each family residing within a sampled household.  Within each family, additional information is collected from one randomly selected adult (the “sample adult”) aged 18 years or older and (if applicable) one randomly selected child (the “sample child”) aged 17 years or younger.  In rare instances when a sample adult is physically or mentally unable to respond, proxy responses are accepted (< 1.5% of sample).  In 2010, NHIS interviews were conducted in 34,329 households, accounting for 89,976 persons in 35,177 families. The estimates presented in this paper are based on data collected from 27,157 sample adults. The household response rate was 79.5%, the conditional sample adult response rate (i.e., the response rate for those sample adults identified as eligible) was 77.3%, and the final sample adult response rate (i.e., the response rate that takes into account both the conditional sample adult response rate and the household/family response rate) was 60.8%. 

The questionnaires, data, and more details about the survey methods are available at http://www.cdc.gov/nchs/nhis.htm. Information from survey questions regarding employment status and the industry and occupation of those currently employed was obtained from the Sample Adult core module.  Demographic characteristics were obtained from questions asked in the Household and Family core modules. 

Occupational Health Supplement

The National Institute for Occupational Safety and Health (NIOSH) sponsored an occupational health supplement (OHS) to the 2010 NHIS to collect information on the prevalence and correlates of work-related health conditions and exposures to potential psychological and physical occupational hazards in the U.S. working population. The OHS questions were embedded within the Sample Adult questionnaire. The 2010 NHIS sample included 17,524 sample adults who had worked at least part of the 12 months preceding their interviews; most of the OHS questions focused on these respondents.

The last NHIS-OHS was conducted in 1988. The 2010 NHIS-OHS includes similar questions to the 1988 supplement about dermatitis, carpal tunnel syndrome and occupational asthma and questions on other topics (e.g., psychosocial exposures) have been adapted from other validated survey instruments, where possible. Data from the OHS can be combined with data from the core NHIS questionnaire for analysis of relationships between occupational exposures and other common health conditions and interactions between occupational and non-occupational factors (e.g., tobacco use, physical activity). The OHS questions are embedded within the Sample Adult questionnaire.

Summary of the content of the 2010 NHIS-OHS

Ethics Board Approval and Consent

The 2010 National Health Interview Survey (NHIS) was approved by the Research Ethics Review Board of the National Center for Health Statistics (Protocol #2009-16) and the U.S. Office of Management and Budget (Control #0920-0214). Written consent for participation in the 2010 NHIS was not received, but instead all 2010 NHIS respondents provided oral consent prior to participation.

Study Definitions

Employment status as of the week prior to the interview was asked of all adults (individuals 18 years or older). Answers put respondents into one of five categories: employed (“working for pay at a job or business” or “with a job or business but not at work”), unemployed (“looking for work”), unpaid worker (“working, but not for pay, at a family-owned job or business”), non-worker (“not working at a job or business and not looking for work”), and unknown. Respondents were also asked if they had ever worked (yes, no, unknown).

The NHIS obtains verbatim responses from each employed adult respondent (age 18 years and over) regarding his/her industry (employer’s type of business) and occupation (employee’s type of work).  In 2010, supplemental questions were added to insure that these data were collected for both current and longest-held jobs of each employed respondent.  These responses were reviewed by U.S. Census Bureau coding specialists who assigned 4-digit industry and occupation (I&O) codes based on the 1997 North American Industrial Classification System (NAICS) and 2000 Standard Occupational Classifica­tion (SOC) system.  To protect respondent confidentiality and allow for more reliable estimates, the public use dataset contains less detailed 2-digit I&O recodes.  The occupation recodes include 94 detailed categories and 23 simple categories, and the industry recodes include 79 detailed categories and 21 simple categories.  The sector profiles are mainly based on the detailed industry recodes, which approximate 3 digit NAICS codes; but, some categories in the profiles were derived by NIOSH from the 4-digit I&O codes through an agreement with the NCHS Research Data Center.  The categories used for each sector were based on the preferences/requests of the sector leadership.

Different reference periods were used for different outcomes. Respondents were asked if they had experienced dermatitis or carpal tunnel syndrome during the past 12 months. The NHIS variable AASSTILL was used to identify workers who had ever been diagnosed with asthma and still had asthma.  The following work organization factors and psychosocial, physical and chemical exposures were analyzed for all adult respondents who were currently employed or employed in the past 12 months: non-standard work arrangement, temporary position, non-standard shift, hostile work environment, exposure to potential skin hazards at work, exposure to outdoor work, and exposure to secondhand smoke. The questions relating to job insecurity and work-family imbalance were only analyzed for those adults currently employed. Data on number of hours worked per week were only analyzed for respondents with one current job.  The question about exposure to vapors, gas, dust, or fumes at work was related to the respondent’s longest-held job, while respondents were asked to relate all of the other workplace exposure and work organization questions to their current jobs.

Data Analysis

After merging the NHIS adult and person files, the prevalence rates of the occupational health supplement’s variables (health outcomes, work organization factors and psychosocial, physical and chemical exposures) among currently employed civilian workers by I&O categories were calculated.  We excluded respondents coded to the military specific occupation category or the Armed Forces industry category (N = 42) from further analyses because the NHIS sample is not designed to provide accurate estimates of persons in the Armed Forces.  The analyses were completed using SAS (version 9.2) survey procedures. Weights were applied in the calculation to obtain proper estimation for the target population, and the Taylor series linearization method was used for variance estimation to account for the complex sample design which involves stratification, clustering, and multistage sampling.  We used the population survey unit, stratum, and sample adult weights provided by NCHS.The minimum sample size for the industry and occupation subgroups presented in these profiles is 5 respondents.

 

 
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