Approaches to Calculation of Average Exposure in Analysis of Epidemiologic Cohorts

• Activity Number: 34
• Type: Contributed
• Date/Time: Sunday, August 4, 2013 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Leonid Kopylev*+
• Companies: US EPA
• Keywords: cumulative exposure ; average exposure

Abstract

There are two different ways of calculating average exposure metric in occupational cohorts. Both use cumulative exposure as the numerator, but one uses the duration of exposure and another uses the length of employment, as the denominator. The former approach is normally used to calculate average exposure when detailed exposure history is available, and the latter is used to calculate de facto exposure when exposure history is less detailed. Both approaches yield the same result when all the workers are exposed over the entire duration of employment. The differences between the two approaches are investigated for a large occupational cohort exposed to acrylonitrile, with detailed exposure data. The cumulative exposure divided by the length of employment is a significant predictor of the lung cancer mortality in this study, while cumulative exposure divided by the duration of exposure is not. Results suggest that both approaches should be considered when calculating an average exposure metric in the analysis of epidemiologic data. DISLAIMER: The views expressed are those of the author and do not necessarily reflect the views or policies of the US Environmental Protection Agency