Study: Beauty and the breast: hair product use and breast cancer risk

IN-DEPTH REVIEW OF RESEARCH

Study background:

Exposure to carcinogens in hair products and increased breast cancer risk has been explored previously, mostly in animal models. This study looked at possible associations between breast cancer and hair product use in African American (AA) and White women. The study was conducted by Adana A.M. Llanos and colleagues from Rutgers University and published in June 2017 in the journal Carcinogenesis. The results seem to indicate an association between hair product use and increased breast cancer risk; that risk differed by race, and in some cases, subtype of breast cancer.  However, researchers cautioned that more studies are necessary in humans to confirm that certain hair products increase breast cancer risk.

Researchers examined data of 4,285 women taking part in the Women's Circle of Health Study (WCHS). In that study, women were asked questions on many factors that might affect breast cancer risk: history of personal and family health, exposure before birth, use of hormones, reproductive history, physical activity, alcohol use, smoking history, vitamin use, and hair product use.

Researchers of this study wanted to know:

Whether the use of hair products (dyes, relaxers, straighteners) increases breast cancer risk in AA and White women.

Population(s) looked at in the study:

This study looked at data collected from 2002 to 2014 from the WCHS case-control study conducted in New York City and 10 counties in New Jersey. Eligible participants were ages 20-75 and able to complete an interview in English. A total of 4,285 women were included in the present analysis:

• 2,280 had a breast cancer diagnosis (cases) 
  • 1,508 of these were AA
  • 772 were White 

2,005 had no history of breast cancer (controls)

• 1,290 of these were AA 
• 715 were White  

Study findings: 

Hair dye and breast cancer risk:

• For AA women
  • Those who reported use of dark shades of hair dye had a 51% increased risk of breast cancer.
• For White women
  • No comparable increase was seen.

Relaxers and breast cancer risk:

• For AA women, regular use of hair relaxers was not associated with increased breast cancer risk.
• In White women, although relaxer use was very low, use alone or together with hair dyes was associated with a 74% increase in breast cancer risk.

The researchers also looked at hair product use and increased risk of estrogen receptor-positive (ER+) vs. estrogen receptor-negative (ER-) breast cancer, because of the marked increase in ER+ cancers in the United States, and to see whether certain hair products might mimic estrogen or trigger a change in the body that somehow increases production of estrogen.

Among the 2,280 women with breast cancer: 

• In AA women, an increased risk of ER+ breast cancer was associated with use of:
  • darker shades of hair dye
  • hair dye more than twice per year
  • hair dye applied in a salon   
• In White women, use of relaxers or straighteners, either alone or together with hair dyes increased risk of ER-negative disease although in this study, the number of White women who regularly used relaxers or straighteners was very small. 

Limitations:

This study had several limitations. Because it was a retrospective case-control study (it retroactively compared people who had breast cancer with those who did not) researchers could not establish cause and effect. Recall bias also limited the results—the WCHS study relied on each participant to accurately remember and report her use of hair care products over the course of her lifetime. Nor did the current study ask women what brands of products they used, so researchers weren't able to identify links between cancer and specific ingredients. Lastly, due to the small number of ER+ breast cancer cases, more studies are needed to confirm the link between hair product use and this type of breast cancer.

Conclusions:

These findings suggest that there may be a link between hair products and breast cancer risk. The authors state that additional studies are needed to further determine if there is a link between hair product use and increased breast cancer risk.

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Posted 9/27/17