How do the genes we inherit from our parents and the characteristics of our bodies affect our risk of developing breast cancer?
The following factors can increase the risk of breast cancer developing
As you get older, your risk of breast cancer increases. At least four out of five of all breast cancer cases in the UK are in women over the age of 50. The disease is uncommon in women under the age of 40.
There isn’t anything we can do about getting older. But all women should be breast aware. Women aged 50 to 70 are eligible for breast screening on the NHS and should receive an appointment every three years. In England the programme is being extended to include women aged 47 to 73.
Women over 70 can continue to access screening by making their own appointments through their doctor or local breast screening unit.
Women are much more likely to get breast cancer than men, so simply being a woman means you are at higher risk of developing the disease.
For women, being taller slightly increases the risk of developing breast cancer. Conversely, being shorter slightly decreases risk.
Height is determined by the combination of our genes, nutrition and hormone levels during our developing years, but we still don’t know exactly how height influences breast cancer risk.
Women who started their periods at an early age have a slightly increased risk of breast cancer. The earlier you began your periods, the higher your risk, but this effect is small and gradual.
Your risk of breast cancer will not be dramatically increased if you started your periods just before 13 (which is the average age). The increase in risk of breast cancer seen with early puberty is probably because these women are exposed to the naturally occurring female hormone oestrogen for longer than women who started their periods later.
In a small number of cases, breast cancer runs in the family. Of all women who develop breast cancer, up to 15% has a significant family history of the disease and about one in 20 has inherited a fault in a gene linked to breast cancer.
The cells in our bodies each contain thousands of genes, which we inherit from our parents. These provide instructions to tell our cells how to function. People who have inherited faults in known breast cancer genes – such as BRCA1 or BRCA2 – have an increased risk of developing breast cancer.
People with a family history of breast cancer tend to have an unusually high number of close relatives (parents, siblings or children) on one side of the family who’ve experienced breast cancer and/or relatives who developed breast cancer at a young age. When thinking of family history, you should look at your mother’s and father’s side of the family separately.
If you have concerns about any cancers in your family then you should see your doctor.
Watch our animation to find out how faulty breast cancer genes are inherited:
For information about UK services for people with a family history of breast cancer please see our family history guide.
High breast density
The amount of tissue compared to fat in your breasts is known as ‘breast density’. Having high breast density (a low proportion of fat) is one of the biggest risk factors for breast cancer. Unfortunately, most women will not know their breast density and there are no established ways to reduce it.
The density of your breasts tends to gradually fall over time, but because age is also a risk factor for breast cancer, this does not mean that your risk of breast cancer reduces as your breasts change. In fact, your risk of breast cancer increases as you get older.
All women should be breast aware. If you notice any unusual changes to your breasts, check this with your doctor.
Women who go through the menopause later than average have a slightly increased risk of breast cancer. The later you go through menopause, the higher your risk, but this effect is small and gradual. Your risk of breast cancer will not dramatically increase if you enter the menopause just after 52 (which is the average age in the UK).
The increase in risk of breast cancer seen in women who have a late menopause is probably because these women are exposed to the naturally occurring female hormone oestrogen for longer than women who go through the menopause earlier.
Other breast conditions (proliferative benign breast disease)
There are many types of benign (non-cancerous) breast conditions and most do not affect the risk of developing breast cancer. However, if you have a benign breast condition where the breast cells are described as ‘proliferative’ (meaning the cells are growing too quickly) then your risk of breast cancer will be increased.
Benign breast conditions where the cells are proliferative are uncommon. Most benign breast conditions (for example, cysts and simple fibroadenomas) do not increase the risk of breast cancer.
If you have had a diagnosis of a benign breast condition and are unsure or worried about your breast cancer risk, you should speak to your doctor.
Your ethnic background affects your risk of developing breast cancer. Studies based in England show a white woman is more likely to develop breast cancer than a black, Asian, Chinese or mixed-race woman.
The difference in risk of breast cancer across different ethnic groups may be due to genes, although more research is needed to determine how much this plays a part. The difference could also be due to different cultures and lifestyle choices, such as the age women have their first child and the number of children they have.
We know that people of certain ethnic groups have a higher risk of breast cancer because they are more likely to carry certain faults in their genes. For example, Ashkenazi Jewish and Icelandic women have a higher risk of carrying inherited faults in breast cancer genes, such as BRCA1 or BRCA2, which are known to increase the risk of developing breast cancer.
For the following factors, there is some scientific evidence that suggests they may affect the chances of developing breast cancer
More research is needed before we can be sure whether or not they are definitely linked to the disease.
Bigger size at birth
It is possible that women who were longer or heavier when born have a slightly greater risk of developing breast cancer than women who were smaller or lighter at birth.
We don’t know exactly why this might occur, but there are a number of possible explanations:
- Exposure to different levels of hormones in the womb may not only affect the size of a baby but also her risk of breast cancer in adult life.
- Women who were longer at birth tend to be taller adults, and being tall slightly increases a woman’s risk of breast cancer.
- Being longer at birth is associated with early puberty, which is also associated with a slightly increased risk of breast cancer.
Results of studies looking at a possible link between miscarriage and breast cancer do not all agree. A few studies looking at whether or not there is a link between miscarriage and breast cancer have not found a link.
It is possible that there might be a link for women who have had more than one miscarriage, or that having a miscarriage increases a woman’s risk of getting breast cancer later in life, when she has been through the menopause.
More research is needed before we can be sure whether or not miscarriage affects breast cancer risk, and how.
The following factors are unlikely to affect breast cancer risk
For these factors, the overall scientific evidence suggests they aren’t linked to the disease. In some cases there simply isn’t any evidence of a link; in others, research has shown there’s no link.
It is unlikely that having an induced abortion (a planned termination out of choice or medical necessity) affects your risk of developing breast cancer.
Some people claim that having an abortion increases the risk of breast cancer because it disrupts the natural development of breast cells during pregnancy, making them susceptible to changing into cancerous cells. This claim is not supported by scientific or clinical evidence.
Information last reviewed: July 2015
Next review due: July 2018
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