Hair
straightening chemicals not linked to breast cancer risk in
African-Americans
PHILADELPHIA
- Chemical “relaxers” used to straighten hair are not associated with
an increased risk of developing breast cancer among African-American
women, say researchers who followed 48,167 Black Women’s Health Study
participants.
In the May issue of Cancer Epidemiology, Biomarkers & Prevention,
researchers from Boston University and Howard University Cancer Center
found no increase in breast cancer risk due to the type of hair relaxer
used or the frequency and duration of use. Women who used relaxers seven
or more times a year over a 20 year span or longer had the same risk as
women who used the chemicals for less than a year, researchers say.
“This is good news,” said the study’s lead investigator, Lynn
Rosenberg, Sc.D., professor of epidemiology at Boston University School of
Public Health. “The present study is definitive that hair relaxers
don’t cause breast cancer, as much as an epidemiologic study can be.”
Previous research shows that breast cancer incidence is higher among
African-American women age 40 or younger than among Caucasian women of the
same age, and this increased risk is not fully explained by known risk
factors, such as race and family history. At all ages, African-American
women are more likely to die of breast cancer than are Caucasian women. To
shed light on these findings and to study potential causes of breast
cancer and other serious illnesses that affect black women, the Black
Women’s Health Study was launched across the United States in 1995. More
than 59,000 women completed an initial questionnaire and more than 80
percent have answered follow-up questions every two years since, including
questions about use of hair relaxers.
Hair relaxers can enter the body through cuts or lesions in the scalp.
These products are not fully monitored by the Food and Drug
Administration, and thus could contain potentially harmful compounds,
Rosenberg said. Manufacturers of hair relaxers and hair dyes are not
required to list all ingredients of their products on the packages, as
some may be considered trade secrets, she said.
“Because hair relaxers are more widely used by younger African-American
women than they are used by older African-American women, a connection
with increased risk of breast cancer in younger women seemed possible,”
Rosenberg said. “Also, millions of African-American women use hair
relaxers, and substances that are used by millions of women over a span of
many years should be monitored for safety.”
The researchers found that younger women used hair relaxers more than
older women did. They also discovered that the majority of women used hair
relaxers before age 20 and a third used the chemicals at least seven times
a year. But when they examined the association between use of hair
relaxers and breast cancer, based on 574 newly diagnosed cases of breast
cancer identified during the follow-up period, they found no connection
between use of relaxers and breast cancer incidence overall or among the
younger women, even if use had been frequent and of long duration.
The study was funded by the National Cancer Institute. Co-authors include
Julie Palmer, Sc.D., and Deborah Boggs, M.S., of Boston University School
of Public Health, and Lucile Adams-Campbell, Ph.D., of Howard University
Cancer Center.
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