A case-control study was conducted to assess whether occupational radiation exposure among men was associated with Down syndrome in their children. The investigators matched cases and controls on age of the mother at childbirth by 5-year categories.
1. When possible, information on paternal radiation exposure was taken from employment records rather than from subject interviews. Why was this done?
O To minimize recall bias of exposure
O To minimize detection bias for cases
O To minimize differential misclassification of exposure
O To remove selection bias of non-radiation exposed fathers
O To provide dose-response information