Study design, sampling and assessment methods of the European study 'abuse of the elderly in the European region'

Background: Violence against and abuse of older persons (VAO) aged > 60 years has become a prominent public health issue. From January 2009-July 2009, we conducted the cross-sectional European study 'Abuse of the elderly in the European region' (ABUEL) among community-dwelling elderly populations aged 60-84 years in Germany, Greece, Italy, Lithuania, Portugal, Spain and Sweden. We describe the cooperation, completion and response rates; the modes of recruitment and administration; and analyse differences in response rates between countries. Methods: We calculated the population fraction (respondents in each age/sex group divided by the population in the same age/sex group) and the population fraction ratio (PFR) to describe and analyse heterogeneity between countries. To analyse associations between methods and response rates we conducted cross tabulations and logistic regression analyses. Results: The response rates ranged from 18.9% in Germany to 87.4% in Portugal. Men were underrepresented in all countries (PFR < 1). Cluster- and cohort-based sampling produced the highest overall response rates. Conclusion: More European and international studies investigating response behaviour in VAO research systematically are needed to gain further knowledge about the internal and external validity of research on VAO.