Attribution-NonCommercial 3.0 United States

This is an open access article, originally published at https://doi.org/10.2147/VHRM.S152173
Except where otherwise noted, this item's license is described as Attribution-NonCommercial 3.0 United States This is an open access article, originally published at https://doi.org/10.2147/VHRM.S152173