Background: This paper discusses whether baseline demographic, socio-economic, health variables, length of
follow-up and method of contacting the participants predict non-response to the invitation for a second
assessment of lifestyle factors and body weight in the European multi-center EPIC-PANACEA study.
Methods: Over 500.000 participants from several centers in ten European countries recruited between 1992 and
2000 were contacted 2–11 years later to update data on lifestyle and body weight. Length of follow-up as well as
the method of approaching differed between the collaborating study centers. Non-responders were compared with
responders using multivariate logistic regression analyses.
Results: Overall response for the second assessment was high (81.6%). Compared to postal surveys, centers where
the participants completed the questionnaire by phone attained a higher response. Response was also high in
centers with a short follow-up period. Non-response was higher in participants who were male (odds ratio 1.09
(confidence interval 1.07; 1.11), aged under 40 years (1.96 (1.90; 2.02), living alone (1.40 (1.37; 1.43), less educated
(1.35 (1.12; 1.19), of poorer health (1.33 (1.27; 1.39), reporting an unhealthy lifestyle and who had either a low
(<18.5 kg/m2, 1.16 (1.09; 1.23)) or a high BMI (>25, 1.08 (1.06; 1.10); especially ≥30 kg/m2, 1.26 (1.23; 1.29)).
Conclusions: Cohort studies may enhance cohort maintenance by paying particular attention to the subgroups
that are most unlikely to respond and by an active recruitment strategy using telephone interviews.