The Connection Between Breast Cancer & Heart Disease

We dismiss our risk of heart disease because we’re so paranoid about breast cancer. Yet the two may be linked. Epidemiologist Dale Sandler, PhD, of the National Institute of Environmental Health Sciences, told MORE how decreasing your risk for one disease may help protect you against the other.

Q. You’re an epidemiologist studying breast cancer. How does heart disease fit into the picture?

A. It may sound like a reach, but it’s not. Our research program, the Sister Study, looks at the impact of environmental exposures and genes on the development of breast cancer. In other words, we want to find out whether breast cancer risk is influenced by the things we eat, the household products we use, the places we live, work, or play. To do this, we’re following 50,000 American women who do not have breast cancer but are about twice as likely to develop it because they have a sister who has had breast cancer.

We’re collecting information on diet, lifestyle, reproductive history, occupation; exposure to things at home, at work, or in the community; and medical history — focusing not just on the present but also early reproductive years and even childhood. We also ask the participants about their mothers’ pregnancies, in hopes of getting clues about the in utero environment, which might also influence their risk. We’re measuring blood pressure on everyone who enrolls and collecting information on their family history of heart disease. We’re also planning to look at relationships between environmental and reproductive factors and cardiovascular disease. I speculate that some of the same things that make these women more at risk for cancer (such as specific lifestyle factors and genes) may make them at increased risk for heart disease as well.

Q. So the cancer-heart disease connection is…?

A. Many of the same factors that increase your risk for breast cancer may also increase your risk for illnesses such as heart disease and diabetes. These risk factors include obesity, lack of exercise, inflammation, and more. And some of these are things we have real control over. So we may be able to change the course as well as the impact of these dread diseases. Changes you make in your lifestyle and environment to reduce your risk for one disease may protect you from the other.

Q. Potentially, will your study help us look at cancer and heart disease in a new way? Perhaps as diseases of lifestyle or of the environment?

A. We know that environment is important in breast cancer, because fewer than 10 percent of women with breast cancer have a known breast cancer gene. Trends in cancer rates over time and place are consistent with an environmental role, and some environmental exposures — such as radiation — have been consistently linked with breast cancer. The timing and dose of your exposure to environmental risks, combined with your genetic makeup, may play critical roles in your disease susceptibility. But of course, more studies are needed.

Q. Do you think that disease risk could be inherited through behavior rather than genes? Can parental behavior (diet, not exercising, smoking, not seeing a doctor regularly) influence the behavior of their children and increase the risk of disease?

A. That’s an interesting and important question. We know now that the contribution of breast cancer genes to your overall breast cancer risk is very small. And there are no heart disease genes equivalent to BRCA1 and BRCA2. But the increase in disease risk due to family history is undoubtedly attributable to shared lifestyle and environment as well as shared genes. Educational levels are similar in families; diets are similar. Lifestyle factors — such as smoking, drinking, exercising, and hobbies — are also likely to be more similar than between unrelated people. We hope the Sister Study will identify the links between these shared environmental and lifestyle factors and disease.

To Join the Sister Study

You may be eligible for the Sister Study if your sister had breast cancer and you haven’t, you are between the ages of 35 and 74, and you live in the United States or Puerto Rico. To volunteer or to learn more about the study, call 877-4-SISTER or click on one of the links below.

Originally published in MORE magazine, September 2006.

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