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Work-Related Lung Disease Surveillance System (eWoRLD)

Methods: Morbidity

Prevalence (Asthma, Chronic Obstructive Pulmonary Disease, and Smoking)

The estimated prevalence of asthma, chronic obstructive pulmonary disease (COPD), and cigarette smoking was based on public-use data from the National Health Interview Survey (NHIS) (http://www.cdc.gov/nchs/nhis.htm). Asthma was defined as a "yes" response to the question "Have you ever been told by a doctor or other health professional that you had asthma?" Current asthma was defined as a "yes" response to the question "During the past 12 months, have you had an episode of asthma or an asthma attack?" COPD was defined as a "yes" response to either of the following questions: (1) "During the past 12 months, have you been told by a doctor or other health professional that you had chronic bronchitis?" or (2) "Have you ever been told by a doctor or other health professional that you had emphysema?" Cigarette smoking status was classified in three groups: nonsmokers, former smokers, and current smokers. Nonsmokers were defined as those who smoked fewer than 100 cigarettes during their entire life. Former smokers were defined as those who smoked at least 100 cigarettes in their entire life and do not currently smoke.

Data on current industry and occupation were collected from all individuals who were employed during the week before the interview took place. Industry and occupation titles are ranked by the estimated prevalence of asthma, chronic obstructive pulmonary disease, and smoking. The industry titles were coded either to the 1987 Standard Industrial Classification (SIC) system, 1995 SIC, 1997 North American Industry Classification System (NAICS), or 2007 NAICS, depending on the survey year. The occupation titles were coded either to the 1987 Standard Occupational Classification (SOC) system, 1995 SOC, or 2000 SOC, depending on the survey year. The National Center for Health Statistics (NCHS) recodes the industry and occupation response values to a 2-digit code and these coding categories are provided in the NHIS sample adult file section for each survey year, and can be accessed on the NCHS website at http://www.cdc.gov/nchs/nhis/quest_data_related_1997_forward.htm.

Estimated prevalences of asthma, COPD and smoking status by gender, current industry and occupation were calculated using sample weights and adjustment for non-responses. For asthma and COPD, prevalences were also calculated by smoking status. Survey respondents with unknown or missing information were excluded from the denominator when calculating a weighted estimate for the prevalence of asthma. SAS® software (SAS Institute Inc., Cary, NC) was used to analyze data and to calculate the estimated frequencies, variances, and prevalences with corresponding 95% confidence intervals.

Prevalence (Coal Workers' Pneumoconiosis)

Prevalence of coal workers' pneumoconiosis (CWP) is reported by tenure and time period. The Coal Workers' Health Surveillance Program (CWHSP) defines radiographic evidence of CWP in chest x-rays as the presence of either small opacities with a profusion category greater than or equal to International Labour Office (ILO) category 1/0, large opacities (i.e., larger than one centimeter in diameter), or both. Administrative and regulatory guidelines have varied over the life of the program. The prevalence of CWP is presented by underground coal mining tenure of miners who participated in the surveys. Tenure calculations were based upon the work histories reported by each miner at the time of the examination. For presentations by five-year periods, only the most recent examination in that period was used for miners with more than one radiograph.

Incidence (Occupational Respiratory Illnesses)

Estimated numbers of work-related respiratory illness (with days away from work) and incidence rates of occupational respiratory conditions due to toxic agents were generally abstracted from the Bureau Labor Statistics annual reports of occupational injuries and illnesses.

Association of Occupational and Environmental Clinics Diagnoses and Hazards

The frequency distributions of work-related respiratory conditions diagnosed in the Association of Occupational and Environmental Clinics (AOEC) and the respiratory hazards associated with these respiratory diagnoses were tabulated from summary reports prepared by AOEC. For hazards other than asbestos, only the top two are listed and the number in parentheses represents the number of diagnoses associated with that reported hazard. The list of the most frequently associated respiratory hazards (excluding asbestos) is a partial listing of all occupational hazards associated with the work-related respiratory conditions. All remaining occupational hazards are aggregated in an "All other" category.

Discharges from Short-Stay Non-federal Hospitals (Asbestosis, Coal Workers' Pneumoconiosis, Silicosis)

Estimated numbers of discharges from short-stay non-federal hospitals were tabulated from the National Hospital Discharge Survey (NHDS) data files provided by the National Center for Health Statistics. Estimated numbers were based on any mention of asbestosis, coal workers' pneumoconiosis, or silicosis from among the seven diagnosis codes provided in the data files for discharged patients who were of age 15 years and older.

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