Authors’ contributions
protocol/project
G. Hilde: protocol/project development, data collection, data analysis, manuscript writing; J. Stær-Jensen: protocol/project development, data collection, manuscript editing; F. Siafarikas: protocol/project development, data collection, manuscript editing; M. Ellström Engh: protocol/project development, manuscript editing; K. Bø: idea of the study, protocol/project development, project leader, data analysis, manuscript writing/editing.