Published Online: June 8, 2015. doi:10.1001/jamainternmed.2015.2147.
Study concept and design: All authors.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Grey.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Wang.
Study supervision: Grey.
Conflict of Interest Disclosures: None reported.
Funding/Support: This study received funding support from the Health Research Council of New Zealand and the University of Auckland.
Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Additional Contributions: Greg Gamble, MSc, University of Auckland, provided advice about data presentation and analysis.