Abstract B69: Mediated effects of social cognitive theory variables on physical activity in Hispanic breast cancer survivors
Authors: Mama Scherezade K. , McNeill Lorna H. , Ortiz Alexis , Tirado-Gomez Maribel , Palacios Cristina , Hughes Daniel C. , Basen-Engquist Karen 
Published: October 2015

Abstract
Purpose: The vast majority of long-term cancer survivors are insufficiently active, and breast cancer survivors are more likely to report being physically inactive and sedentary than prostate or colorectal cancer survivors. Social cognitive theory (SCT) has been used to understand physical activity adoption and maintenance in the general adult population and among breast cancer survivors, but no study to date has explored SCT influences on physical activity exclusively among Hispanic cancer survivors, who are at greater risk of not meeting leisure-time physical activity guidelines and disproportionately suffer from comorbidities, such as cardiovascular disease and diabetes. Thus, the purpose of this study was to determine the effect of a culturally-tailored exercise intervention on physical activity and sedentary behavior in Hispanic breast cancer survivors and to determine whether intervention effects were mediated by changes in SCT variables, including exercise self-efficacy, barriers self-efficacy, social modeling and social support.
Method: Project VIVA! was a 16-week randomized controlled trial to test the effectiveness and feasibility of a culturally tailored exercise intervention for Mexican American and Puerto Rican breast cancer survivors in Houston, Texas and San Juan, Puerto Rico. Eligible women (N=93) who self-identified as Mexican American residing in Houston, TX or Puerto-Rican residing in San Juan, PR were randomized to a 16-week culturally-tailored (n=30) or standard (n=31) exercise intervention or a wait-list control (n=32) group. Women completed questionnaires on social cognitive influences, physical activity and sedentary behavior and completed a 7-day accelerometer protocol at baseline and post-intervention. Paired sample t-tests were used to assess changes in physical activity, sedentary behavior, and SCT variables over time across groups, and repeated measures analyses were used to assess changes over time by group. Mediation analyses were used to determine whether intervention effects on physical activity and sedentary behavior were mediated by changes in exercise self-efficacy, barriers self-efficacy, social modeling and social support after controlling for age and education.
Results: On average, participants were middle-aged (M age=55.5 years, SD=9.9) and most (52.1%) had completed some college or more. At baseline, women reported doing roughly 11.6 minutes of physical activity and walking per day and were sedentary over 6 hours per day. Across groups, women reported increases in vigorous (t=2.7, p=.008), moderate (t=2.6, p=.011) and total (t=2.7, p=.008) physical activity and exercise self-efficacy (t=3.2, p=.002) from baseline to post-intervention. There were no significant differences in changes in physical activity or SCT variables over time by group. Although the intervention did not have a direct effect on physical activity or sedentary behavior, it had an indirect effect on sedentary behavior. Increases in social modeling significantly mediated the association between intervention group assignment and decreases in sedentary behavior (Indirect effect=4.5, 95% CI: 0.4, 12.4) among Hispanic breast cancer survivors, controlling for age and education.
Conclusions: Results suggest that Hispanic survivors may benefit the most from exercise interventions that focus on increasing social norms for physical activity and social modeling from friends and family members. Future interventions should include friends and family members of Hispanic breast cancer survivors to support them to be active and less sedentary and to be physically active with them. Further research is needed to explore additional mediators of change in physical activity and sedentary behavior in Hispanic breast cancer survivors in an effort to reduce health disparities and decrease risk of cancer recurrence and comorbidities.
Citation Format: Scherezade K. Mama, Lorna H. McNeill, Alexis Ortiz, Maribel Tirado-Gomez, Cristina Palacios, Daniel C. Hughes, Karen Basen-Engquist. Mediated effects of social cognitive theory variables on physical activity in Hispanic breast cancer survivors. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B69.