Using Isotemporal Analyses to Examine the Relationships Between Daytime Activities and Cancer Recurrence Biomarkers in Breast Cancer Survivors

Physical Activity and Breast Cancer Survival-Epidemiologic Evidence and Potential Biologic Mechanisms

PURPOSE OF REVIEW

To review the biologic mechanisms that may be operative between physical activity and survival after breast cancer.

RECENT FINDINGS

Physical activity decreases risk of mortality from breast cancer by up to 40%. Several biologic mechanisms have been hypothesized to explain this association. Previous cohort studies and randomized trials have examined the primary mechanisms that appear to be operative, which involve a decrease in sex hormone levels, insulin resistance, and inflammation. The evidence is still inconsistent and several limitations in the existing literature exist. Understanding the biologic mechanisms involved in the association of physical activity and breast cancer survival will provide more precision to physical activity guidelines for cancer survival. To achieve this objective, future research should include direct measurements of physical activity, sedentary behaviour, and health-related fitness to provide a more comprehensive assessment of these factors and their association with biomarkers and survival after breast cancer.

Substituting bouts of sedentary behavior with physical activity: adopting positive lifestyle choices in people with a history of cancer

Purpose

To determine in people with a history of cancer, whether substituting sitting time with other daily activities (i.e., sleeping, walking, moderate and vigorous physical activity) was associated with changes in waist circumference (WC), an important surrogate marker of cardiometabolic risk.

Methods

Cross-sectional analyses from the Atlantic Partnership for Tomorrow’s Health (Atlantic PATH) cohort was conducted using isotemporal substitution models to explore the associations of substituting sedentary time, physical activity behavior (International Physical Activity Questionnaire), or sleep (Pittsburgh Sleep Quality Index) with changes in WC. Analyses were conducted using sex-specific WC classifications.

Results

In 3,684 people with a history of cancer [mean age (SD) 58.2 (7.3) years; BMI 28.9 (5.2) kg m⁻²; 71% female], reallocating 10 min of sleep or sedentary time for 10 min of walking was associated with lower WC in women (p < 0.01). In men, PA intensity appeared to be more strongly associated with a reduced WC. Replacing 10 min of sedentary time with 10 min of moderate or vigorous PA and replacing 10 min of sleep with moderate PA were associated with a significantly reduced WC (p < 0.001). The largest effect was when 10 min of moderate PA was replaced with vigorous PA, a reduction in WC (p < 0.01) was evident.

Conclusion

For people with a history of cancer, adopting small but positive changes in lifestyle behaviors could help reduce WC and potentially offset negative health-related outcomes associated with higher WC. Further research is required to examine whether such an intervention may be acceptable and manageable among this population.