Social-cognitive, demographic, clinical, and health-related correlates of physical activity and sedentary behaviour in newly diagnosed women with breast cancer.

Purpose: Identifying correlates of physical activity and sedentary behaviour allows for the identification of factors that may be targeted in future behaviour change interventions. This study sought to determine the social-cognitive, demographic, clinical, and health-related correlates of physical activity and sedentary behaviour in individuals recently diagnosed with breast cancer.

Methods: Data were collected from 1381 participants within 90 days of diagnosis in the Alberta Moving Beyond Breast Cancer (AMBER) Cohort Study. Physical activity and sedentary behaviour were measured with ActiGraph GT3X+® and activPAL devices, respectively, for seven consecutive days. Correlates were collected via a self-reported questionnaire, medical record extraction, or measured by staff.

Results: Multivariable models were fitted for sedentary behaviour, light physical activity, and moderate-to-vigorous physical activity. Greater sedentary behaviour was associated with higher body fat percentage (BF%) (ß=0.044; p<0.001) and being single (ß=0.542; p<0.002). Lower light physical activity was associated with higher BF% (ß=-0.044; p<0.001), higher body mass index (ß=-0.039; p<0.001), greater disease barrier influence (ß=-0.006; p<0.001), a HER2-positive diagnosis (ß=-0.278; p=0.001), and being single (ß=-0.385; p= 0.001). Lower moderate-to-vigorous physical activity was associated with higher BF% (ß =-0.011; p=0.001), greater disease barrier influence (ß=-0.002; p<0.001), and being of Asian (ß=-0.189; p=0.002) or Indian/South American (ß=-0.189; p=0.002) descent. Greater moderate-to-vigorous physical activity was associated with having greater intentions (ß=0.049; p=0.033) and planning (ß=0.026; p=0.015) towards physical activity.

Conclusion: Tailoring interventions to increase physical activity for individuals recently diagnosed with breast cancer may improve long-term outcomes across the breast cancer continuum.