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Comparison of the sociodemographic characteristics of the large NutriNet-Santé e-cohort with French Census data: The issue of volunteer bias revisited

par Andreeva, Valentina;Salanave, Benoît;Castetbon, Katia ;Deschamps, Valérie;Vernay, Michel;Kesse-Guyot, Emmanuelle;Hercberg, Serge
Référence Journal of epidemiology and community health, 69, 9, page (893-898)
Publication Publié, 2015-09

Article révisé par les pairs

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Résumé :

BACKGROUND:A recurring concern in traditional and in Web-based studies pertains to non-representativeness due to volunteer bias. We investigated this issue in an ongoing, large population-based e-cohort.METHODS:The sample included 122 912 individuals enrolled in the Internet-based, nutrition-focused NutriNet-Santé study between May 2009 and March 2014, with complete baseline data. Participants were recruited via recurrent multimedia campaigns and other traditional and online strategies. Individuals aged 18+ years, residing in France and having Internet access, were eligible for enrolment. Their sociodemographic characteristics were compared with the corresponding 2009 Census data via χ(2) goodness-of-fit tests. The effectiveness of statistical weighting of the e-cohort data was also explored.RESULTS:The sample exhibited marked geographical and sociodemographic diversity, including volunteers belonging to typically under-represented subgroups in traditional surveys (unemployed, immigrants, the elderly). Nonetheless, the proportions of women, relatively well-educated individuals and those who are married or cohabiting, were notably larger compared with the corresponding national figures (women: 78.0% vs 52.4%; postsecondary education: 61.5% vs 24.9%; married or cohabiting: 70.8% vs 62.0%, respectively; all p<0.0001).CONCLUSIONS:There were notable sociodemographic differences between the general French population and this general population-based e-cohort, some of which were corrected by statistical weighting. The findings bear on the potential generalisability of future investigations in the context of e-epidemiology.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.