Breast cancer is the most common cancer in the UK. One out of every eight women and one out of every 870 men will develop breast cancer in their lifetime. Most breast cancers (80%) occur in women over the age of 50.
We don’t fully understand why some people get breast cancer and some don't. Research suggests that breast cancer is caused by lots of different factors, many of which we can’t control.
A small number of people diagnosed with breast cancer (5%) have inherited a fault in one of the known breast cancer genes.
Risk tells us the chance of something happening. You might hear risk talked about in terms of ‘absolute risk’ and ‘relative risk’.
Absolute risk measures the chances (odds) of something happening over a period of time. For example, the risk of developing breast cancer in your lifetime. Absolute risk is often reported as a figure such as 1 in 8 (12%). It does not compare the risk of breast cancer to anything else.
Relative risk compares risk in different groups of people. For example, the risk of developing lung cancer in people who smoke compared to people who don’t smoke. This type of risk is often reported using a comparison, such as ‘smokers are five times more likely to develop lung cancer than non-smokers’.
Headlines on breast cancer ‘causes’, or ‘breast cancer is linked to…’ stories are frequently in the news. However, when you look behind the headlines the true story can be very different.
Some news stories about breast cancer risk are based on limited or questionable research, or involve only a small number of people. Sometimes the results are exaggerated or reported in a misleading way and the increase in risk – if proved at all – is very small.
If a breast cancer risk story worries you, finding out more about the research behind the headline can help you decide what that risk may mean to you. The NHS website looks at the facts behind the headlines. You can also call 0808 800 6000 to talk to us about any breast cancer risk story that concerns you.
Research has shown that different things can increase or decrease the risk of getting breast cancer. These are called 'risk factors'. But we are all different, so risk factors will not affect us all in the same way. One person may have many risk factors and not develop breast cancer, while another may have very few and be diagnosed with it.
The three main risk factors for developing breast cancer are:
- being female
- getting older
- significant family history of breast cancer
We have developed a handy graphic (PDF) about the main risk factors for breast cancer. These risk factors are discussed below.
Being a woman is the single biggest risk factor for developing breast cancer. More than 62,000 new cases of breast cancer are diagnosed each year in the UK, of which only about 370 are diagnosed in men.
After being female, age is the most significant risk factor for developing breast cancer. The older you are, the higher your risk. Most breast cancers (80%) occur in women over the age of 50. Most men who get breast cancer are over 60.
Significant family history
Having someone in your family with breast cancer doesn’t automatically mean your own risk is increased. For most people, having a relative with breast cancer does not increase their risk.
However, a small number of women and men have an increased risk of developing breast cancer because they have a significant family history. A family history is significant if there are:
- a number of people who have had breast and ovarian cancer in the family
- family members who have been diagnosed with breast cancer at a young age
- male relatives who have been diagnosed with breast cancer
Our pages on breast cancer in families have more information about this.
Other factors can slightly increase the risk of developing breast cancer, including:
Risks linked to our bodies
The female hormone oestrogen plays a role in the development of breast cancer.
Women who start their periods before the age of 12 or who have a late menopause have a small increased risk of developing breast cancer. This is thought to be because they are exposed to oestrogen for longer than women who start their periods later or have an early menopause.
Not having children or having your first pregnancy over the age of 30 may also slightly increase your risk.
Being overweight increases your risk of developing breast cancer after the menopause. This is thought to be because after the menopause, body fat produces oestrogen.
Having previously had breast cancer
Women who have already had breast cancer are at an increased risk of getting breast cancer in the same or opposite breast.
Having dense breast tissue
Breasts are described as being dense if they have less fatty tissue and more glandular and fibrous tissue. Women with dense breasts have a higher risk of developing breast cancer.
Some benign (not cancer) breast conditions
There are many different benign breast diseases and most do not increase the risk of developing breast cancer. However there are some that may increase the risk.
Risks linked to lifestyle and life choices
Taking hormone replacement therapy (HRT) after the menopause
Studies have shown that taking HRT increases the risk of developing breast cancer. The risk is related to how long HRT is taken for. However, the risk of developing breast cancer starts to reduce once you stop taking HRT.
Taking the oral contraceptive pill
Taking the oral contraceptive pill slightly increases the risk of developing breast cancer. However the risk reduces when you stop taking the pill and after 5–10 years is about the same as it would have been if you had never taken it.
Studies have shown that drinking any amount of alcohol increases the risk of developing breast cancer. The more you drink the greater the risk is.
There is some evidence that smoking may increase the risk of developing breast cancer. The risk appears to be greater for women who started smoking at a young age and continue to smoke for many years.
Risks linked to the environment
Radiotherapy to the chest area can slightly increase your risk of developing breast cancer. The risk is higher for people who have had radiotherapy to the chest for Hodgkin lymphoma.
Being exposed to high levels of ionising radiation following a radiation plant accident or radiation explosion increases the risk of developing many types of cancer, including breast cancer.
Medical x-rays use a very low dose of ionising radiation. The amount of radiation you are exposed to while undergoing medical x-rays is usually very low. The amount you receive is strictly controlled.
Unproven/conflicting risk factors
There are a number of risk factors that you might read or hear about in the news where there is either no, little or conflicting evidence of an increased risk. These include:
- in vitro fertilisation (IVF)
- having an abortion
- an injury to the breast (for example, bumping into something)
- using deodorants and antiperspirants
- chemicals in the environment
- shift work
You can find out more information about these on the Cancer Research UK website.
The three main risk factors for developing breast cancer are not things we can control.
There are other risk factors that might reduce the risk of developing breast cancer but which we still can’t control, for example starting your periods before the age of 12.
You can try to reduce your risk by making changes to your lifestyle. This may also help improve your general health. For example:
- maintaining a healthy weight, especially after the menopause
- eating a healthy diet
- getting some regular exercise
- not drinking more alcohol than the recommended daily amount, or cutting out alcohol completely
Making lifestyle choices may not prevent you from getting breast cancer and it’s important to consider the overall effect your choices may have before making any decisions. For example:
- having a baby at a young age would have a far greater impact on your life in general than on reducing your breast cancer risk
- you may decide after talking to your GP that the benefits of taking HRT outweigh the potential small increase in breast cancer risk
Some research suggests that taking aspirin or ibuprofen can reduce the risk of breast cancer. However, regularly taking these drugs solely for this purpose is not recommended. This is because these drugs can have side effects when taken long term, and we don’t know enough about how they affect breast cancer risk.
Your individual risk is unique and can change over time – for example, as you get older or if your family history changes (by someone in your family being diagnosed with cancer). When thinking about lifestyle changes, decide what’s best for you at this time in your life.
You might want to talk with your GP or practice nurse for further information. You can also call our Helpline on 0808 800 6000.