The Individual and Joint Effects of Cardiorespiratory Fitness and Body Mass Index and Breast Cancer Incidence and Mortality.
Approved Research ID: 52609
Approval date: April 17th 2020
Breast cancer is the most commonly diagnosed cancer in women. Approximately 1 in 8 women are expected to develop breast cancer in their lifetime. Having obesity has been shown to increase the risk of developing breast cancer in women who are postmenopausal but decrease risk in premenopausal women. Obesity has also been associated with higher risk of dying from breast cancer, regardless of menopausal status. In parallel, being physically active is associated with a lower risk of developing and dying from breast cancer. Further, physical activity and weight are known to be simultaneous targets of breast cancer prevention initiatives, yet very few studies have examined their combined association with breast cancer. However, assessment of physical activity is known to be problematic for people with excess weight. This may mean it may not be the best measure to disentangle the effects of weight and physical activity on breast cancer risk. Cardiorespiratory fitness (CRF) assesses the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscles during physical activity. CRF has been proposed as an alternative assessment to physical activity as it is more representative of the health benefits associated with being active. However, only one study has examined the impact of CRF on breast cancer mortality, and like physical activity, being more physically fit was associated with a lower risk of dying from breast cancer. Therefore, we will determine if CRF is associated with a women's risk of developing and dying from breast cancer. We will also see if CRF changes the way that weight (assessed using body mass index) is associated with a women's risk of developing and dying from breast cancer. This project is part of a PhD students dissertation work, and therefore will take approximately three years to complete. We have an increasingly aging population and rates of obesity continue to rise, suggesting more women will be at increased risk for breast cancer. Thus, there is a need for a greater understanding of ways that we can reduce risk. This study will improve our understanding of CRF, a novel breast cancer risk factor, and body mass index, an established breast cancer risk factor. This information could be used by health care providers to better target women for breast cancer prevention and increase knowledge for patients about factor that influence their risk of getting breast cancer and what they can do to reduce this risk.
The objective of this study is to examine the independent effects cardiorespiratory fitness (CRF), and the joint effects of CRF and body mass index (BMI) on breast cancer incidence and mortality. As such we propose three specific aims:
- Examine the association between CRF and breast cancer incidence and mortality.
- Examine the joint effects of CRF and BMI on breast cancer incidence and mortality.
- Examine the causal relationship between CRF, BMI and breast cancer risk using mediation analysis.
We wish to extend this scope to also look at the combined association of CRF with percent body fat or physical activity on the risk of breast cancer incidence or mortality. This would result in three additional aims:
1. Examine the joint association of CRF and percent body fat on breast cancer incidence and mortality
2. Examine the joint association of CRF and physical activity on breast cancer incidence and mortality
3. Examine the causal association between CRF with percent body fat or physical activity on breast cancer risk using mediation analysis