Baseline and follow-up characteristics of participants and nonparticipants in a randomized clinical trial of multifactorial fall prevention in Denmark

OBJECTIVES: To address the external validity of a trial of multifactorial fall prevention through an analysis of differences between participants and nonparticipants regarding socioeconomic and morbidity variables. DESIGN: Analysis of nonresponse in a randomized clinical trial. SETTING: Geriatric outpatient department. PARTICIPANTS: One thousand one hundred five community-dwelling adults aged 65 and older who had sustained at least one injurious fall. MEASUREMENTS: Marital status, housing tenure, income, comorbidity, hospitalization, fractures, and drug use before invitation to participate in the trial. Fractures, hospitalization and death were measured for 6 months of follow-up. RESULTS: Four hundred forty-seven responding nonparticipants and 266 nonresponding nonparticipants were compared with 392 participants in the trial. Lower income (odds ratio (OR)=2.38, 95% confidence interval (CI)=1.28-4.28) and more days of hospitalization during the previous 5 years (OR=1.96, 95% CI=1.15-3.33) predicted responding nonparticipation; independent predictors of being a nonresponding nonparticipant were unmarried status (OR=2.0, 95% CI=1.36-2.94), lower income (OR=4.74, 95% CI=2.30-9.78), more days of hospitalization (OR=3.49, 95% CI=1.99-6.11), and prior fractures (OR=1.56, 95% CI=1.02-2.38). Nonresponding nonparticipants were significantly more likely to die (OR=12.99, 95% CI=1.6-105.6) or be hospitalized (OR=2.66, 95% CI=1.7-4.1) than participants during 6 months of follow-up. CONCLUSION: Nonresponding nonparticipants of a trial of multifactorial fall prevention differed significantly from participants in terms of socioeconomic and morbidity variables and were more likely to be hospitalized or die during 6 months of follow-up. Because of the differences between the two populations, it is questionable whether results from this randomized trial can be generalized to people potentially eligible for participation.