Research has found that smoking may be a potential risk factor for developing breast cancer. People who currently or previously smoked may have an increased chance of developing this condition. Although there are many other breast cancer risk factors that you have no control over, quitting smoking is one thing you can do to help support breast health.

About 14 percent of adults in the United States are smokers. At least 16 million people in the U.S. have a health condition that is caused by cigarette smoke. Smoking can cause several health conditions, including heart disease, diabetes, lung disease, and immune system conditions. Smoking can also lead to lung cancer and other types of cancer, including colon cancer, cervical cancer, mouth or throat cancer, stomach cancer, and leukemia.

Does Smoking Cause Breast Cancer?

Doctors don’t know the exact cause of any one case of cancer. However, researchers have found that certain genetic, environmental, and lifestyle factors can lead to a higher risk of breast cancer. Several recent studies have shown that cigarette smoke may be one such breast cancer risk factor.

One study found that people who had ever smoked cigarettes were 6 percent more likely to develop breast cancer compared to people who had never smoked. Another large study estimated that this number was closer to 14 percent. Some evidence also shows that exposure to secondhand smoke may increase a person’s risk of breast cancer.

Studies in this area sometimes find differing results. Researchers in each study may use different methods or study different groups of people. Plus, a person’s risk of breast cancer may partly depend on other characteristics. Scientists are still learning about how smoking and breast cancer are linked for different individuals.

Smoking Risk in Different Groups of People

How often a person smokes may affect breast cancer risk. One study found that people who smoked for at least 40 years had a 57 percent increased chance of being diagnosed with breast cancer compared to people who had never smoked. In addition, people who smoked 40 cigarettes per day were 21 percent more likely to be diagnosed with breast cancer.

Starting cigarette smoking early in life may also play a role. People who begin smoking as teens may be at higher risk than those who started smoking when they were older. In addition, women who start smoking before their first pregnancy have higher rates of breast cancer than women who start smoking after. Breast tissue continues to develop once a woman gives birth. After this point, researchers think that breast cells may be more resistant to damage from cigarette smoke.

Other breast cancer risk factors are also important to consider. Smokers who have a family history of breast cancer are 35 percent more likely to develop breast cancer than never-smokers. For people who have never had a parent or sibling with breast cancer, smoking still increases risk, but not as much.

Why Is Smoking Linked to Cancer?

There are a couple of reasons why smoking may cause cancer. First, tobacco smoke contains toxic substances that damage the DNA within cells. DNA contains genes that tell the cell what to do and when to grow. When a cell experiences gene changes, it may turn cancerous, growing out of control.

Cigarette smoking can also contribute to cancer through the immune system. Normally, the body’s immune system helps keep cells under control, killing any cells that are behaving abnormally. People who smoke have weakened immune systems, making it harder for the body to slow down or stop cancer cells.

Vaping and Breast Cancer Risk

In recent years, vaping — with e-cigarettes, vape pens, Juul devices, or similar products — has become increasingly popular. These devices don’t contain tobacco, so many people believe that they are not as harmful as cigarettes. However, they do contain nicotine and carcinogens (chemicals that are known to cause cancer).

Because vaping is so new, medical researchers haven’t studied its long-term effects. They don’t yet know whether vaping leads to breast cancer. However, some early studies show that there may be a link. One laboratory study found that e-cigarettes could make breast cancer cells grow more quickly and resist death. Another found that e-cigarette exposure made breast cancer cells more likely to spread to the lungs. However, studies in this area have not yet been conducted in humans.

Smoking and Breast Cancer Treatments

Smoking not only increases breast cancer risk; it can also lead to complications — health problems that develop while someone has a disease or is undergoing treatment.

Many people with breast cancer undergo surgery. However, smokers are more likely to die or to develop serious health conditions during and after surgery. Smoking can also make it harder to recover from surgical procedures.

Smoking also increases the chances that someone will have lung damage while they undergo radiation treatments. In addition, people who smoke are more likely to have blood clots when they use hormone therapy drugs.

Smoking and Breast Cancer Outlook

Cigarette smoking may lead to a worse breast cancer prognosis (outlook). One study found that current smokers diagnosed with breast cancer have:

• A 41 percent higher chance of relapse (having the cancer return after being treated)
• A 60 percent higher risk of dying from cancer
• More than double the risk of dying from any cause

It is important to note that not all studies have seen these same effects. Another study of people with breast cancer found that relapse rates and survival rates were similar among smokers and nonsmokers. However, this study only looked at people with estrogen receptor-positive, HER2-negative cancer caught at an early stage. More research is needed in this area.

How To Protect Breast Health

There are many other breast cancer risk factors besides smoking. Many of these are things that cannot be changed, such as:

• Age
• Dense breast tissue (having high levels of connective tissue and low levels of fat tissue in the breasts)
• Starting menstrual periods before turning 12 years old
• Entering into menopause after turning 55
• A family history of breast cancer
• A history of other breast conditions
• Receiving radiation therapy as a child, teen, or young adult

However, there are several other risk factors that are under your control. If you are worried about breast cancer risk, you can help support breast health by focusing on these other factors.

Exercise

People who don’t get much physical activity have a higher likelihood of developing breast cancer. Doctors recommend exercising for at least a half an hour per day, five days per week. This can also help you maintain a healthy weight. Being overweight or obese is another breast cancer risk factor.

Certain Medications

Some women use hormone replacement therapy (HRT) during menopause to help relieve symptoms. However, using HRT drugs leads to a somewhat increased risk of breast cancer. Some birth control pills — also called oral contraceptives — can elevate a person’s chances of having breast cancer. People worried about breast cancer risk who are considering these treatments may want to ask their doctor about alternatives.

Alcohol Consumption

Another risk factor that can be controlled is drinking alcohol. People who drink more are more likely to develop breast cancer. The effects of drinking and smoking seem to build upon each other. People who both drink alcohol and smoke cigarettes have the highest risk of breast cancer — more so than people who drink but have never smoked and people who smoke but don’t drink.

Quitting Smoking

Quitting smoking is another way to lower breast cancer risk. Several studies have found that the longer a person smokes, the higher their breast cancer risk. Quitting now may mean that you are less likely to be diagnosed with cancer in the future.

Even reducing the number of cigarettes you smoke per day may help. One study found that the more cigarettes a person smoked each day, the higher their risk of breast cancer. People who smoked many cigarettes per day had a higher risk than those who just smoked a few. However, people who only had a couple of daily cigarettes still had a slightly increased risk.

Once smoking has become a habit, it is very hard to quit. Many people have trouble doing it on their own. Fortunately, there are many medications and treatments that can make it easier. Talk to your doctor if you are struggling with quitting. Also, the American Lung Association and the American Cancer Society both offer programs that can help people quit. These programs provide people with additional information, offer tools to help people stay on track, and help connect people with others who are trying to quit.

Share Your Experiences With Others

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 53,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Are you living with breast cancer? Are you trying to quit smoking? Share your experiences in the comments below, or start a conversation by posting on MyBCTeam.