aCenter for Population Health Research, University of Montana, Missoula, Montana

bInstitute for Health Research, Kaiser Permanente Aurora, Colorado

cDepartment of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado

dSchool of Public and Community Health Sciences, University of Montana, Missoula, Montana, USA

Correspondence to Sarah Y. Michels, MPH, Center for Population Health Research, University of Montana, 32 Campus Drive, Skaggs 173, Missoula, MT 59812, USA. Tel: +1 406 243 4430; e-mail: [email protected]