National Institute of Environmental Health Sciences   —  National Institutes of Health   —  U.S. Department of Health and Human Services

The Sister Study

The information we get from every single participant really makes a difference.

Breast Cancer Research in the Sister Study — 20 years and still going strong!

Dear Sisters,

How time flies. It is hard to believe that as of October 2023 the Sister Study is celebrating its 20th anniversary of breast cancer research. It was Fall of 2003 when we recruited our first participant, and about five years later when the study surpassed its goal of 50,000 participants. The terrific response from Sisters across all 50 states and Puerto Rico and your dedication to the study over the years is an accomplishment to be proud of. We could not have reached this milestone without you.

You've devoted your time and shared very personal information with us to help us learn how we might change our environments to reduce the occurrence of breast cancer. You provided us with samples and information about your family histories, your lifestyles, and your health. Some of you even answered our call to participate in a video about the study (The Sister Study 20th Anniversary Video).

While many of you have been following our accomplishments through our Facebook group and other outlets, I am excited to share a compilation of research highlights, and a new video about the study that is available on this website. You may also notice that we've changed the look of our logo and website to mark this milestone and to make it easier to find the new materials we developed with you in mind.

The website, video, and other updates feature some of the many people (sorry we could not include everyone!) who contributed to the success of the study — from our fabulous study staff, Sisters who partnered with us to spread the word about the study, the many early-career and established researchers who have used data from the study for scientific discovery, and of course the thousands of women who make up the Sister Study. The 10-minute video also includes some of the past and current leaders at NIEHS who continue to support the study.

With your help, Sister Study researchers have published more than 300 scientific papers, some of which are highlighted in the video and elsewhere on the website.

Breast cancer is a complex disease for which many factors play a role. While there is no one single risk factor that accounts for a substantial proportion of breast cancer (well, other than age and being female), the study has discovered many factors that may contribute to a woman's chances of developing breast cancer—including air pollution, early life trauma and psychosocial stress, dietary factors, permanent hair dyes and chemical hair straighteners, some other personal care products, and obesity. The study has also discovered how exposure-related changes to DNA may influence biological aging and breast cancer risk. A full listing of research publications from the Sister Study is available on our Research Publications page and some of the highlights from those papers are available on our 20th Anniversary Research Highlights page.

We are extremely grateful for all the women who've participated in the study. There would be no Sister Study without you. It is only fitting that during this month of October dedicated to Breast Cancer Awareness that we also take a minute to acknowledge all the Sisters we have lost over the years. The Sister Study is for all those women who are no longer with us, and for future generations of women who we want to be healthy and free of breast cancer, as they lead us into the future. There is still much we need to learn about this and other diseases that impact women.

We plan to continue the study for many years to come — and in fact there are some important new topics for our next round of follow-up questionnaires that you may find interesting—for example, hair texture, tattoos, sunscreen use, factors related to climate resilience such as use of air conditioners and air filters, and questions about cancer recurrence. We also will be reaching out to some of you about a new effort to collect another round of biological samples (including blood, urine, and even stool samples for microbiome research) so that we can better account for change in environmental exposures over time. We hope you will all stay engaged and continue to answer our calls for information.

Thank you again for your continued participation in the Sister Study.

Dale Sandler, Ph.D., lead researcher for the Sister Study




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