Demographic, clinical, psychosocial, and environmental correlates of objectively assessed physical activity among breast cancer survivors

Purpose
The aim of this study was to identify demographic, clinical, psychosocial, and environmental correlates of objectively assessed physical activity among breast cancer survivors.

Methods
Baseline data were utilized from 574 female breast cancer survivors who participated in three different intervention studies: Resistance and Endurance exercise After ChemoTherapy (REACT), Exercise and Nutrition Routine Improving Cancer Health (ENRICH), and Move More for Life (MM4L). Participants were eligible if they were aged ≥18 years and had completed primary cancer treatment. Physical activity was objectively assessed by accelerometers or pedometers. Participants completed self-reported questionnaires on demographic, psychosocial, and environmental factors. Information regarding clinical factors was obtained from medical records or patient self-report. Multivariable linear regression analyses were applied on the pooled dataset to identify factors that were significantly correlated with physical activity. In addition, the explained variance of the model was calculated.

Results
The multivariable regression model revealed that older age, (β = −0.01, 95 %CI = −0.02; −0.003), higher body mass index (β = −0.05, 95 %CI = −0.06; −0.03), lower self-efficacy (β = 0.2, 95 %CI = 0.08; 0.2), and less social support (β = 0.1, 95 %CI = 0.05; 0.2) were significantly correlated with lower physical activity. This model explained 15 % of the variance in physical activity.

Conclusion
Age, body mass index, self-efficacy, and social support were significantly correlated with objectively assessed physical activity in breast cancer survivors. It may therefore be recommended that physical activity intervention studies in these women target those who are older, and have a higher body mass index, and should operationalize behavior change strategies designed to enhance self-efficacy and social support.

Trial registration
The REACT study is registered at the Netherlands Trial Register [NTR2153]. The ENRICH study is registered at Australian New Zealand Clinical Trials Register [ANZCTRN12609001086257]. And the MM4L study is registered at Australian New Zealand Clinical Trials Register [ACTRN12611001061921]