1. Division of General Medicine, Section for Research, Beth Israel Deaconess Medical Center , Boston, Massachusetts , USA
2. Harvard Medical School , Boston, Massachusetts , USA
3. Kaiser Permanente Center for Health Research , Portland, Oregon , USA
4. Department of Nutrition, Brigham and Women’s Hospital , Boston, Massachusetts , USA
5. Health Behaviour and Policy, School of Medicine, Virginia Commonwealth University , Richmond, Virginia , USA
6. Johns Hopkins School of Medicine , Baltimore, Maryland , USA