Objective: Participation bias may be a problem in couple-based psychosocial studies. Therefore, it is important to investigate the characteristics associated with participation. The aim of this study was to analyze whether participation in a longitudinal psychosocial questionnaire study among couples affected by breast cancer was associated with socioeconomic, breast cancer-specific, and other health-related characteristics of the patients and partners.
Methods: The analyzes are based on 2254 couples who were invited to participate in a nationwide survey on psychosocial adjustment among couples dealing with breast cancer. Participating couples (N = 792) were compared with non-participating couples (N = 1462) with regard to socioeconomic and health-related characteristics obtained from nationwide clinical and administrative registers.
Results: Associations were seen between various socioeconomic variables and couple participation. The patient characteristics older age (OR = 0.15 [95% CI = 0.07-0.55]), low education (OR = 1.95 [95% CI = 1.46-2.68]), disability pension (OR = 0.59 [95% CI = 0.39-0.55]), or non-western ethnicity (OR = 0.36 [95% CI = 0.15-0.82]) reduced couple participation. The partner characteristics older age (OR = 0.23 [95% CI = 0.15-0.43]), low education (OR = 1.67 [95% CI = 1.25-2.22]), receiving disability pension (OR = 0.46 [95% CI = 0.25-0.82]), non-western ethnicity (OR = 0.17 [95% CI = 0.06-0.49]), or high morbidity (OR = 0.76 [95% CI = 0.60-0.96]) also reduced couple participation. Furthermore, couples with low income (OR = 1.49 [95% CI = 1.16-1.95]) had reduced participation. No associations were found between couple participation and breast cancer-related variables.
Conclusions: Socioeconomic characteristics of patients and partners, and morbidity of partners may influence participation in couple-based psychosocial breast cancer research. Breast cancer-related characteristics do not seem to influence participation.