Guest Editorial The “Cytokine for Gerontologists ” Has Some Company

FRAILTy has long been recognized as a complex syn-drome of failure to thrive in the elderly adults. When Fried and colleagues (1) suggested the first comprehensive definition for frailty, they helped set in motion many studies of this complex condition; three more of these are published in this edition of the Journal. Even earlier, Rosenberg (2) had proposed sarcopenia as a term to describe the loss of muscle with normal aging, in parallel with osteopenia, and had suggested that sarcopenia was an important part of the pathophysiology of aging and frailty. The link between sar-copenia, frailty, and inflammation has beguiled researchers for decades, and remains central to our understanding of the pathophysiology of age-related decline in function. Early work by Erschler suggested that interleukin (IL)-6 was an important cytokine in aging, and possibly causal to the development of sarcopenia and frailty (3). But 20 year