About the Authors

Glen E. Duncan

To whom correspondence should be addressed. E-mail: duncag@u.washington.edu

Affiliation Department of Epidemiology, University of Washington, Seattle, Washington, United States of America

Jack Goldberg

Affiliations Department of Epidemiology, University of Washington, Seattle, Washington, United States of America, Vietnam Era Twin Registry, Seattle VA Epidemiologic Research and Education Center, Seattle, Washington, United States of America

Carolyn Noonan

Affiliation Department of Medicine, University of Washington, University of Washington Twin Registry, Seattle, Washington, United States of America

Anne Vernez Moudon

Affiliations Department of Epidemiology, University of Washington, Seattle, Washington, United States of America, Department of Urban Design and Planning, University of Washington, Seattle, Washington, United States of America

Philip Hurvitz

Affiliation Department of Urban Design and Planning, University of Washington, Seattle, Washington, United States of America

Dedra Buchwald

Affiliation Department of Medicine, University of Washington, University of Washington Twin Registry, Seattle, Washington, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: GD JG. Analyzed the data: CN. Wrote the paper: GD. Other: Provided critical feedback on design and analysis: DB GD JG AM CN PH. Evaluated and revised the manuscript: JG DB AM PH CN. Established the twin registry and questionnaire: DB JG.