Department of General Practice and Central Research Unit for General Practice, Institute of Public Health, University of Copenhagen, Denmark. m.vass@dadlnet.dk
AIMS: In controlled intervention studies, a selective non-response or refusal to participate at baseline may bias measurable effects of the intervention. The aim of this study was to compare mortality and nursing home admission among older persons who accepted (participants) and older person who declined (non-participants) to join a controlled feasibility trial, and to describe and evaluate defined subgroups of non-participants. METHODS: Prospective controlled three-year intervention study (1999-2001) in 34 Danish municipalities with five-year follow-up. Randomization and intervention (education of municipality employees) was done at municipality level. In total 5,788 home-dwelling 75- and 80-year-olds living in these municipalities were invited to participate in the study. Written consent was obtained from 4,060 persons (participation rate 71%). RESULTS: During five-year follow-up non-participants had a higher mortality rate (survival analysis risk ratio RR = 1.5, 95% CI = 1.3-1.7, p