Author Contributions: Dr Michels had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Stuebe, Rich-Edwards, Willett, Manson, Michels.
Acquisition of data: Rich-Edwards, Manson, Michels.
Analysis and interpretation of data: Stuebe, Rich-Edwards, Willett, Manson, Michels.
Drafting of the manuscript: Stuebe.
Critical revision of the manuscript for important intellectual content: Rich-Edwards, Willett, Manson, Michels.
Statistical analysis: Stuebe, Rich-Edwards, Willett, Michels.
Obtained funding: Manson.
Administrative, technical, or material support: Manson.
Study supervision: Manson, Michels.
Financial Disclosures: None reported.
Funding/Support: The Nurses’ Health Study and the Nurses’ Health Study II are supported by Public Health Service research grants CA50385, CA87969, and DK58845 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services.
Role of the Sponsor: The National Cancer Institute had no involvement in or control over the design and conduct of the study; the collection, analysis, and interpretation of the data; the preparation of the data; or the preparation, review, and approval of the manuscript.
Acknowledgment: We thank Karen Corsano, BA, Brigham and Women’s Hospital, and Eileen Hibert, MA, MS, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, for technical assistance.