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Open Access Research article

Benefits of extensive recruitment effort persist during follow-ups and are consistent across age group and survey method. The TRAILS study

Esther Nederhof1*, Frederike Jörg12, Dennis Raven1, René Veenstra3, Frank C Verhulst4, Johan Ormel1 and Albertine J Oldehinkel1

Author Affiliations

1 Interdisciplinary Center Psychopathology and Emotion regulation, University Center for Psychiatry, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands

2 Friesland Mental Health Services, Leeuwarden, The Netherlands

3 Department of Sociology, University of Groningen, Groningen, The Netherlands

4 Department of Child and Adolescent Psychiatry, Erasmus University Medical Center, Rotterdam, The Netherlands

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BMC Medical Research Methodology 2012, 12:93  doi:10.1186/1471-2288-12-93

Published: 2 July 2012

Abstract

Background

Extensive recruitment effort at baseline increases representativeness of study populations by decreasing non-response and associated bias. First, it is not known to what extent increased attrition occurs during subsequent measurement waves among subjects who were hard-to-recruit at baseline and what characteristics the hard-to-recruit dropouts have compared to the hard-to-recruit retainers. Second, it is unknown whether characteristics of hard-to-recruit responders in a prospective population based cohort study are similar across age group and survey method.

Methods

First, we compared first wave (T1) easy-to-recruit with hard-to-recruit responders of the TRacking Adolescents’ Individual Lives Survey (TRAILS), a prospective population based cohort study of Dutch (pre)adolescents (at first wave: n = 2230, mean age = 11.09 (SD 0.56), 50.8% girls), with regard to response rates at subsequent measurement waves. Second, easy-to-recruit and hard-to-recruit participants at the fourth TRAILS measurement wave (n = 1881, mean age = 19.1 (SD 0.60), 52.3% girls) were compared with fourth wave non-responders and earlier stage drop-outs on family composition, socioeconomic position (SEP), intelligence (IQ), education, sociometric status, substance use, and psychopathology.

Results

First, over 60% of the hard-to-recruit responders at the first wave were retained in the sample eight years later at the fourth measurement wave. Hard-to-recruit dropouts did not differ from hard-to-recruit retainers. Second, extensive recruitment efforts for the web based survey convinced a population of nineteen year olds with similar characteristics as the hard-to-recruit eleven year olds that were persuaded to participate in a school-based survey. Some characteristics associated with being hard-to-recruit (as compared to being easy-to-recruit) were more pronounced among non-responders, resembling the baseline situation (De Winter et al.2005).

Conclusions

First, extensive recruitment effort at the first assessment wave of a prospective population based cohort study has long lasting positive effects. Second, characteristics of hard-to-recruit responders are largely consistent across age groups and survey methods.