http://www.wsc.ma.edu/medicaltourism/ where tourists could access a survey. We posted some of the basic findings on sustainable medical tourism, but have taken the link down to collect more data. One paper has been published on the USDA-FS website and another paper is currently under a second review for Tourism Review.
Check out the bibliography on the website to see the variety of papers out there on the subject.
http://www.wsc.ma.edu/medicaltourism/medtourbib.htm. Over 212 and counting! If you find a web accessible paper, please send me the details!