Potential confounders
Subjects were initially classified as either smokers or nonsmokers
on the basis of baseline survey, but changes in
smoking habit were recorded in all follow up surveys. All but
10 female workers were non-smokers in the initial cohort,
and five started to smoke during the follow up time. Smoking
at each survey period was measured in unit of pack-years.
Information was also gathered on exposure to indoor
pollutants including cooking fuel type (coal, gas, and
electricity), pets at home, regularly passive smoking either
at home or at work area, and family medical history, focusing
on respiratory diseases in parents (asthma, bronchitis,
emphysema, and lung cancer).
Potential confounders
Subjects were initially classified as either smokers or nonsmokers
on the basis of baseline survey, but changes in
smoking habit were recorded in all follow up surveys. All but
10 female workers were non-smokers in the initial cohort,
and five started to smoke during the follow up time. Smoking
at each survey period was measured in unit of pack-years.
Information was also gathered on exposure to indoor
pollutants including cooking fuel type (coal, gas, and
electricity), pets at home, regularly passive smoking either
at home or at work area, and family medical history, focusing
on respiratory diseases in parents (asthma, bronchitis,
emphysema, and lung cancer).
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