UC San Diego

Introduction

Physical activity can attenuate cancer-related declines in physical functioning, improve emotional well-being, and prolong survival among older (≥65 years) breast cancer survivors. However, factors associated with physical activity among older breast cancer survivors are not well-understood.

Materials and methods

Participants were enrolled in the Women's Health Initiative (WHI) Life and Longevity After Cancer (LILAC) study. Descriptive statistics, multiple linear regression, and relative risk [RR] regression were used to assess the association of demographic, clinical, physical and psychosocial variables with the total duration of and participation in physical activity among postmenopausal breast cancer survivors. Age-specific correlates (65-74 years vs. 75-84 years vs. ≥85 years) of physical activity were also examined.

Results

The majority of participants (n = 3710, mean age = 78.8 ± 5.9) were white (90.7%) and had in situ/localized breast cancer (78.9%). Women who had higher education (RR = 1.47 for graduate/professional school versus high school or less, 95% CI: 1.32, 1.63), higher self-rated health (RR = 1.04 for 10 point increase, 95% CI:1.02, 1.07), higher physical functioning (RR = 1.03 for 5 point increase, 95% CI: 1.02, 1.04), and higher social support (RR = 1.41 for social support all of the time versus none of the time, 95% CI: 1.01, 1.96), were more likely to engage in any physical activity. Similar results were observed for duration of physical activity. Among women aged <75, radiation therapy, but not chemotherapy, was associated with longer duration of total physical activity (adjusted difference = 19.7 min/week, 95% CI: 6.1, 33.3), but was not associated with duration among older women. The association between pain and duration of moderate/strenuous activity also differed with age: among women aged <75, those with moderate pain averaged fewer minutes of moderate/strenuous physical activity than those with no pain (adjusted difference:-14.4 min/week, 95% CI:-28.5, -0.1). However, among women aged ≥85, those with moderate pain averaged more minutes of moderate/strenuous physical activity per week than those with no pain (adjusted difference:16.6 min/week; 95% CI:2.9, 30.3).

Discussion

Multiple factors were associated with physical activity among older breast cancer survivors in the WHI. Future physical activity interventions should focus on age-related (e.g., comorbidities) and treatment-related factors (e.g., radiation) as well as certain subgroups, such as women with higher symptom burden.