The primary focus of my research is the epidemiology of chronic diseases, especially cardiovascular disease and cancer, with a primary methodologic focus on large-scale randomized clinical trials. I have been involved in the design, conduct, analysis, and interpretation of a number of randomized trials and their post-treatment observational follow-up. I served as Principal Investigator of the Women’s Health Study, a randomized trial evaluating the balance of benefits and risks of low dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer among approximately 40,000 female health professionals, and am currently Principal Investigator (with Dr. I-Min Lee) of the extended observational follow-up of the participants. I am Principal Investigator (with Dr. JoAnn Manson) of a just completed trial of vitamin D and omega-3 fatty acids (VITAL) in the primary prevention of cardiovascular disease and cancer among over 25,000 randomized participants, which has just begun its post-treatment observational follow-up phase. I have also served as co-Investigator of both Physicians’ Health Study I and II, which evaluated in large-scale randomized trials the preventive roles of low-dose aspirin, beta-carotene, vitamin E, vitamin C, and a multivitamin on cardiovascular disease, cancer, vision, and cognitive function, and I have served as Principal Investigator (with Dr. Peter Wayne) of  and observational study evaluating the use and effectiveness of a model integrative clinic at Brigham and Women’s Hospital.

I have a longstanding and substantial commitment to teaching and training in epidemiology, both nationally and internationally. I serve as co-Director (with Dr. Paul Ridker) of an NHLBI-funded T32 training grant in the Epidemiology of Cardiovascular Disease, and direct introductory core courses in epidemiology and randomized clinical trials at Harvard T.H. Chan School of Public Health and Harvard Medical School. I am highly involved in career development activities at Brigham and Women’s Hospital, and am co-Chair of the Promotions Committee of the Department of Medicine. I am the Chair of the Harvard Medical School Institutional Review Board, and am a member of the National Cancer Institute Board of Scientific Counselors for Clinical Science and Epidemiology.