Nonparticipation in a Danish cohort study of long-term sickness absence

Pernille Pedersen,¹ Ellen A Nohr,² Hans Jørgen Søgaard<sup>1

1</sup>Psychiatric Research Unit West, Regional Psychiatric Services, Herning, Denmark; ²Department of Epidemiology, Institute of Public Health, University of Aarhus, Aarhus C, Denmark

Aim: The aim of the present study was to identify predictors of nonparticipation in a Danish cohort of individuals on long-term sickness absence with a nonparticipation rate of 53.6%.
Methods: Data from Danish public registers were linked to all 2414 individuals initially recruited to the cohort. Information regarding social- and health-related characteristics was retrieved. Adjusted logistic regression was carried out to examine differences between participants and nonparticipants as well as to identify predictors of nonparticipation.
Results: Nonparticipation was associated with being male, relatively young, having a vocational secondary education, and having a low income, whereas a recent somatic disease treated in hospital was a predictor for participation. Having had a psychiatric disorder in the past was generally a barrier for participation, while a recent psychiatric disorder was a positive factor for participation.
Conclusion: Individuals with low socioeconomic status and individuals with prior psychiatric disorders were less willing to participate in this cohort study of long-term sickness absence.

Keywords: mental disorders, nonparticipation, nonresponse, sickness absence