The Sister Study was established by Drs. Dale Sandler and Clarice Weinberg at the National Institutes of Health / National Institute of Environmental Health Sciences, to investigate environmental and genetic risk factors for breast cancer. The Sister Study cohort includes more than 50,000 women whose sister was diagnosed with breast cancer. On average, women with a sister with breast cancer have twice the risk of developing breast cancer as other women. Sisters also share potentially relevant gene variants and exposures. Thus, the Sister Study provides greater statistical power than a similarly sized general population cohort, especially for studying gene-environment interaction.
The Sister Study launched in July 2003, enrolling volunteers without a history of breast cancer, aged 35-74, residing in the United States and Puerto Rico who had a sister with breast cancer. Enrollment of the cohort of 50,884 closed in March 2009. Targeted recruitment strategies for minority, lower education, and older women were employed to enhance diversity within the cohort.
Baseline data collection included a comprehensive Computer Assister Telephone Interview (CATI) covering residential and occupational history and exposures, sister(s) cancer history, lifestyle factors, socioeconomic factors, anthropometric data, reproductive and medical history, medications, and other potential breast cancer risk factors; self-administered questionnaires on family medical history, early life exposures, diet, and personal care products; and a home visit for collecting biospecimens (first morning void urine, blood, toenail clippings, and household dust), anthropometric and blood pressure data, and a self-administered questionnaire covering exposures in the past 24 hours (prior to biospecimen collection). Exposure date was collected across the life course, including in utero, childhood, adolescence and adulthood exposures.
Follow-up consists of either a brief update on health status and contact information (Annual Health Update) or, every two to three years, a Detailed Follow-Up questionnaire. These Detailed Follow-Up questionnaires track changes in women’s health, lifestyles, and environmental exposures over the course of the study. They also provide an opportunity to collect new data to evaluate emerging hypotheses and in-depth information to update special topics of interest.
When participants report breast cancer or other incident cancers via the periodic follow-ups and through telephone calls, e-mails, or correspondence with the study helpdesk, we seek medical records, pathology reports and/or physician verification (with the consent of the participating woman) to complement self-reported data.
For possible collaborations with NIEHS Sister Study investigators, please see the section for Collaborations and Data Requests.