Breast Cancer Risk Factors
Breast cancer, like many cancers, cannot be attributed to a simple cause. Because of this it is preferable to think in terms of "risks" rather than "causes". A “risk factor” for breast cancer is anything that might cause us to be more likely to develop the disease. Some risks are inherited and we can do nothing to change them; others are incurred throughout our lives. One UK study (1) estimates that 23% of breast cancer cases in the UK are attributable to “modifiable” risk factors and may be preventable through changes to the way we lead our lives. This is equivalent to over 12,500 cases in the UK female population. Other studies suggest this figure is an underestimate, for example a recent French study (2) concluded that 37% of breast cancer cases may be preventable. Below we summarise risk factors associated with breast cancer. Further details about all of these can be found in our Breast Cancer Risk Factors brief.
Risk factors we have no control over
Ageing, being female, inheriting certain single gene mutations (e.g. BRCA mutations), genetic pre-disposition (based on inheriting variation in many genes), family history of breast cancer, tall stature, heavy birthweight, benign breast disease, previous breast cancer diagnosis, high mammographic density (which is partly genetic and partly environmental and changes over a lifetime; it can only be determined by a mammogram).
Risk factors we may have some control over
Weight: being obese or overweight increases risk; try to reduce your weight.
Diet: poor diet (high in fat & sugar, low in vegetables) increases risk; adopt a healthy diet e.g. a Mediterranean-style diet.
Physical activity: physical activity reduces risk; do at least 150 minutes of moderate or 75 minutes of vigorous physical activity weekly.
Alcohol: Alcohol increases risk considerably; consider reducing your alcohol intake to government guidelines of less than 14 units (e.g. 6 glasses of wine) per week or stop drinking alcohol altogether.
Vitamin D: Those with breast cancer have low vitamin D levels; ensure enough exposure to sunlight for adequate Vitamin D production (e.g. 9 minutes of daily sunlight at lunchtime from March to September).
Having children and Breastfeeding: Having children young and breastfeeding reduce risk.
Smoking: Smoking may increase risk, especially if you begin at an early age or have smoked for many years; stop smoking.
Hormonal contraception (e.g. the pill): Taking combined hormonal contraception (synthetic oestrogen and progesterone) increases risk; consider alternative forms of contraception.
Hormone Replacement Therapy: Taking combined HRT increases risk; consider alternative approaches for managing menopausal symptoms.
Radiation: Exposure to high level ionising radiation from medical treatment, especially during puberty, increases the risk of breast cancer. In general it is difficult to avoid, as it is used as an effective cancer treatment.
Environmental risk factors we may have some control over
Endocrine Disrupting Chemicals (EDCs): Exposure to many EDCs may increase risk; avoid exposure to EDCs where possible.
Night Shift Work/Light at Night: Increased light at night increases risk; avoid/minimise shift work if possible; ensure good quality sleep in a dark room.
Residence: Those who live in urban (rather than rural) areas and in areas of higher socio-economic status have an increased risk of breast cancer.
1. Brown K. F. et al. (2018). The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. British Journal of Cancer 118(8): 1130–1141. https://www.nature.com/articles/s41416-018-0029-6
2. Soerjomataram I. et al. (2018). Cancers related to lifestyle and environmental factors in France in 2015. European Journal of Cancer 105: 103-113. https://doi.org/10.1016/j.ejca.2018.09.009
page last updated July 22, 2019