Self-reported flight hours vs. company records for epidemiologic studies of flight attendants.

INTRODUCTION: Although there is increased interest in health effects studies of aircrew members, the differences between self-reported work history and company records, including effects on exposure assessment, are poorly characterized.
METHODS: We collected both self-reported work history and company records as part of a National Institute for Occupational Safety and Health biomonitoring study of reproductive hormones in 45 female flight attendants. These two sources of work history information were compared to identify differences which might impact the assessment of work exposures.
RESULTS: There appeared to be consistent overreporting of self-reported block time and number of flight segments compared with company record-based estimates. Overreporting in turn inflated the assessment of two important exposures: cosmic ionizing radiation estimated dose and time zones crossed. Factors including domicile, block hours per year of work, and length of employment affected the amount and direction of overreporting. Comparison to compensated credit hours, including nonflight hours, did not fully account for the overreporting. DISCUSSION: Self-report of block time may or may not include compensated nonflight hours, resulting in differences when compared to company records. Exposure bias is likely to result if the complexities of self-report are not considered when writing questionnaires. Aircrew members should be asked for additional occupational information, and a comparison of self-report block time to a sample of company records should be considered prior to exposure assessment and epidemiologic analysis.