There’s one thing doctors want women to know after a study linked an increased risk of breast cancer to women who use hair dye or straighteners: Association does not equal causation.
That’s a formal way of saying that you can’t take two events and say one thing causes the other just because it appears there could be a connection.
“I like to tell my patients that breast cancer is like a thousand-piece puzzle,” said Dr. Lori Gentile, a general surgeon who specializes in breast surgery and surgical oncology at Novant Health Carolina Surgical. “If you think of all the risk factors that we know about such as obesity, family history and hormone status, all of those are just small pieces to the puzzle. We can’t just pinpoint it down to one specific piece that causes someone to get breast cancer.”
The risk discussed in the study was significantly higher among black women — six times higher than white women.
While using hair dye or chemical straighteners may increase the risk of breast cancer, Gentile says it’s important to clarify that using these products does not mean you’ll get breast cancer. As she likes to put it, it’s another piece of that thousand piece puzzle.
A deeper look into the study
The study was conducted using data from an ongoing study called the Sister Study—a review conducted by the National Institute of Environmental Health Sciences where participants are women with a sister who had breast cancer.
Researchers also looked at the participants over an eight-year period, where the number of breast cancer cases were tracked as the women aged.
“Age is also a risk factor for breast cancer,” Gentile said. “The frequency of using hair dye is also more likely to be used as people age. So you can’t just say that it’s just the hair dye contributing to the increase in breast cancer.”
While the study did find that risk for breast cancer in black women was significantly higher compared to white women, Gentile points out the proportion difference.
Out of the 46,709 participants, 84% of the women were white. By using such a small population of black women, the research is making the percentage look bigger, Gentile said.
Gentile reminds women that it’s important to look at the whole study before being worried that a trip to the beauty salon puts them at an increased risk for developing breast cancer.
For those who are still worried about the study’s findings, Gentile encourages them to be aware of proven risk factors of breast cancer with longstanding evidence: family history, age, exercise, diet, alcohol consumption, tobacco use and body mass index (BMI).
Early detection is key
Novant Health, along with the American Society for Breast Surgeons and the American College of Radiology, recommends women start getting their annual mammograms at 40.
For those who have a family history of breast cancer, Gentile recommends the woman come in 10 years younger than the earliest onset of breast cancer in the family. For example, if a woman has a family member who got breast cancer at 45 years old, it would be recommended to start annual mammograms at age 35.
In addition to annual mammograms, breast self-awareness (formerly known as breast self-exams) is a good step towards early detection. Breast issues or concerns like a lump, swelling, irritation, redness or discharge should be communicated with your doctor immediately.