“…Three studies use data from the US Health and Retirement Study, with its nationally representative sample of older people Nicholas et al, 2011;Kelley et al, 2011), while Kessler and McClellan (2004) use a large random sample of Medicare beneficiaries. The remaining studies use selective samples, defined either by patient characteristics, for example, high-cost and low-income Medicare beneficiaries , or by care setting, with seven of the studies based on hospital samples (Yoo et al, 2012;Tan and Jatoi, 2011;Zhang et al, 2008;Gade et al, 2008;Teno et al, 1997;Chambers et al, 1994). Some studies use samples defined by both patient characteristics and care setting, for example, patients admitted to an inpatient oncology unit in a US hospital (Tan and Jatoi, 2011).…”