Table 1

Response rates

NW-partNI-partTotal samplea
CasesControlsCasesControlsCasesControls
n%n%n%n%n%n%
Eligible23468242989
Contacted22861002998100791100111710029061003886100
Questionnaire returned193884.8212670.966383.476168.1245484.4281572.4
Included in analysis186781.7205768.663480.268861.6235881.1258866.6
Telephone interview117277.5195765.360676.666259.3223977.0246463.4
  • a One hundred forty-three cases and 157 controls that fulfilled the inclusion criteria of both study parts are counted only once in the total sample.