Footnotes

• Correction notice This article has been corrected since it was published Online First. The author name Sarah McGill has been amended to read Sarah K McGill.

• Contributors SM, TK, RS contributed to the study's concept and design. SM, TK and SF analysed the data. SM drafted the manuscript, which was revised by all coauthors. All authors accepted the final version of the manuscript. RS is guarantor.

• Competing interests None.

• Ethics approval Stanford University and Veterans Affairs Palo Alto Health Care System.

• Provenance and peer review Not commissioned; internally peer reviewed.