- The topic of this study is very relevant to young women concerned about breast cancer risk. The focus of the study is the use of hair care products, hair dyes and straighteners, and their effect on breast cancer risk.
- The study looks at a large group of women, their hair product use and whether they are diagnosed with breast cancer.
- The results are not generalizable because all of the participants are sisters of a breast cancer patient so they do not represent the general population. The frequency of participants with mutations in a breast cancer gene are unknown and not accounted for in this study which limits the findings.
- There are many limitations of this study making is unclear whether these results are actionable.
Strength of Science: Medium-Low
- This study looks whether hair dye and straightener use is associated with increased breast cancer risk. As with all observational studies, the findings could show association but cannot demonstrate that these products cause breast cancer. There are many caveats and limitations of this study. There is the potential that major untested confounding factors truly account for the weak associations observed rather than the hair products suggested.
- This study used participants from the Sister study. Each participant had a sister with breast cancer and therefore this group of participants is different from the general population. The results are not generalizable. The design of this group limits the findings. Furthermore, this study which focuses on hair dye and straightener use only evaluates that use at one point in the study, does not look at potential later use of these hair products and relies on participant recall to accurately self-report hair product use 12 months prior.
- The Sisters study is a prospective study that is they observe participants who are healthy and whether they are later diagnosed with breast cancer or not. However, the evaluation of hair product use in this study is entirely based on past history. This mixed design is not optimal.
- The lack of generalizability and lack of statistical confidence in the data make this study of limited clinical utility. A prospective study with better controlled designed is needed to answer the questions posed.
- There are multiple limitations to this research as outlined in the XRAY review. These limitations indicate that the finding need to be considered with caution and may not reflect any causal relationship between hair products and breast cancer risk.