Certain genes increase your risk of breast cancer. But just because someone in your family has had breast cancer doesn’t mean you’ll get it. Lifestyle factors, like drinking alcohol, can increase your risk.

There are risk factors associated with breast cancer — some you can control, but others you can’t.

Although we don’t cover every risk factor for breast cancer below, these risk factors are the most common and best understood.

About risk factors

Having risk factors for breast cancer doesn’t mean you will develop the disease. It means your chances of getting it are increased.

Many people have one or more risk factors for breast cancer but will never get it.

There isn’t much you can do to change your genetics and personal history, but knowing about them can help you stay vigilant about your health.

1. Sex and age

Sex and age are two of the biggest risk factors for breast cancer that can’t be changed.

Women are more likely to develop breast cancer than men, but this doesn’t mean that some men won’t develop breast cancer.

Breast cancer diagnosis risk in the next 10 years

The National Cancer Institute (NCI) notes that the risk of developing breast cancer increases with age:

  • At age 30 years: 1 in 204
  • At age 40 years: 1 in 65
  • At age 50 years: 1 in 42
  • At age 60 years: 1 in 28
  • At age 70 years: 1 in 24

2. Family history and genetics

Your risk of breast cancer nearly doubles if you have a first-degree relative (parent, sibling, child) who has had breast cancer. And if you have two first-degree relatives, your risk of breast cancer triples.

If you’ve personally received a breast cancer diagnosis, you also have a higher risk of developing cancer in the other breast or a different area of the same breast.

This isn’t the same as the risk of recurrence. Recurrence is when breast cancer that was diagnosed earlier has come back.

Approximately 5% to 10% of breast cancers are hereditary. Most inherited forms of breast cancer are caused by mutations in two genes: BRCA1 and BRCA2, also known as the breast cancer 1 and 2 genes.

This doesn’t automatically mean you’ll develop breast cancer if you have either of the mutations, but your risk of developing breast cancer by age 80 years is about 7 in 10 if you inherit a harmful BRCA gene mutation.

This statistic increases if more of your family members are affected by breast cancer.

3. Reproductive factors and menstrual history

Getting your first period before the age of 12 years or going through menopause after the age of 55 years may increase your risk of breast cancer. This has to do with your exposure to the hormone estrogen.

Additionally, not having children or having your first child after the age of 30 years may increase your risk.

If you’ve given birth, nursing your child after birth may have a protective effect against breast cancer. Research has found that your risk decreases by about 4% for every year you nurse your child.

4. Dense breasts

Dense breasts can make detecting lumps or abnormalities in a mammogram more difficult. But having dense breasts doesn’t increase your risk of dying from breast cancer.

In women age 40 years and older, nearly half have dense breasts, so dense breasts are common. You can’t feel dense breasts during a self-exam, but your doctor can determine your breast density with a mammogram.

Additionally, research suggests that women with dense breasts may be 4 to 6 times more likely to develop breast cancer compared with women with more fatty breasts.

A 2023 review found that women with extremely dense breasts were 2.37 times more likely to develop breast cancer than women with the lowest breast density level.

Talk with your doctor about whether digital or 3D mammograms may be a better option for you if you have dense breasts.

Lifestyle risk factors are ones that you can control and change.

5. Previous radiation to the chest

Having radiation to your chest area for a different kind of cancer in the past increases your risk of developing breast cancer.

6. Diet and exercise

According to a 2023 review of research, a diet that’s high in saturated fat may increase the risk of breast cancer, among other cancers. Common sources of saturated fats include:

  • fatty meats
  • full-fat dairy products
  • palm oils

A 2022 study looked at the effects of a diabetes risk reduction diet, which moderates your consumption of carbohydrates. It found that this diet style contributed to a 0.41 times decreased risk of breast cancer in Middle Eastern women.

A sedentary lifestyle may also increase the risk. High levels of regular physical activity may reduce the risk of breast cancer by up to 10%, a 2024 analysis of 19 cohort studies found.

Another study found that physical activity reduced the risk of premenopausal and postmenopausal breast cancer using data from 47,456 premenopausal and 126,704 postmenopausal between the years 2006 and 2014.

7. Weight

Obesity is an established risk factor for breast cancer, especially in postmenopausal women.

The increased risk is due to the fact that fat cells make estrogen, which increases the amount of estrogen in your body. Having higher levels of estrogen can increase the risk of developing hormone receptor-positive breast cancers.

According to a 2019 study, women who lost weight after the age of 50 years and kept it off had a lower risk of developing breast cancer than women who stayed at the same weight.

8. Alcohol consumption and smoking

Drinking alcohol increases the risk of developing breast cancer. This may be because alcohol can increase estrogen levels and other hormones associated with breast cancer.

According to the NCI, alcohol consumption can affect breast cancer risk in the following ways:

  • Light drinkers: 1.04 times more likely
  • Moderate drinkers: 1.23 times more likely
  • Heavy drinkers: 1.6 times more likely
  • Women who have never smoked: light to moderate drinking are 1.13 times more likely

A 2023 study out of Spain found that postmenopausal women with overweight or obesity who smoked less than 10 pack-years (the amount a person has smoked over a long period of time) or 10 to 25 pack-years had a reduced risk of all breast cancers.

This is compared to those who smoked more than 25 pack-years, which showed no reduced risk of breast cancer.

You can opt to avoid alcohol if you drink. You can also try a smoking cessation program if you currently smoke.

9. Hormone therapy

A number of studies have shown that the use of hormone replacement therapy (HRT) may increase breast cancer risk quite substantially, especially with HRT that includes both progesterone and estrogen.

The use of HRT may also increase the risk of recurrence in breast cancer survivors.

Research indicates that those who used hormone therapy for menopause are also at an increased risk of breast cancer.

Your risk increases the longer you use hormone therapy.

Most people have one or more risk factors for breast cancer. Your risk isn’t due to just one factor, but often because of a combination of different factors.

You can change some risk factors, like your diet or exercise levels, but you don’t have control over others like your age or genetics.

Talk with your healthcare team about the risk factors that you might have and how to best address them.