Attrition in a panel study of people with environmental exposures: new insights about the impact of race, sex, and number of children in the household.

This study examines attrition in a panel survey. Each member of the panel was selected because of their documented exposure to long-term, low levels of hazardous substances in their residential water. In addition, each was informed of their exposure at the time of baseline contact. The analytic approach involves examining the interactive effect of race and sex, as well as the additive effect of household characteristics on the propensity to stay. The data are derived from the National Exposure Registry, which is a large-scale, longitudinal health survey. This study finds that compared with white males, non-white males are more likely to attrite and white females are more likely to stay in the study. In addition, the propensity to stay is affected by the number of children in the household. These findings have implications for field procedures that may involve the selective targeting at baseline of those subgroups with a greater propensity to attrite.