Our study is one of the first to show that preoperative frailty is prevalent in older patients awaiting major noncardiac surgery, and that it is independently associated with postoperative delirium occurrence.
Our finding that one-third of the patients had a frailty score of 3 or more is similar to that reported by a previous study showing that 27% of older patients admitted to a Veterans Hospital were considered frail (6
). Patients awaiting major surgery may have co-existing surgical conditions such as osteoarthritis that may produce symptoms similar to those observed in the frail elders. However, our finding that preoperative frailty independently predicts postoperative delirium suggests that the frailty score reveals risk that is not captured by traditional risk factors for delirium such as advanced age, functional dependence, cognitive frailty and depression.
A previous study in older surgical patients found that frailty, as defined by the Edmonton Frail Scale, was associated with postoperative complications, but the measurement of postoperative delirium in this study was only through chart review and likely underestimated its occurrence (7
). In the Rush Memory and Aging Project, a longitudinal study of aging (8
) increasing frailty was found to be associated with incident Alzheimer’s disease and rate of cognitive decline. Other studies reported that signs of frailty such as grip strength, gait disturbance, and body composition, have been related to mild cognitive impairment (9
Taken together, factors associated with the development of frailty and cognitive changes may share a common etiology. For example, a history of cerebrovascular disease has been related to both postoperative delirium (13
) and frailty (14
). Inflammatory markers such as C-reactive protein or proinflammatory interleukins have been implicated in frailty (15
) and cognitive impairment (16
), but their relationship to postoperative delirium remains to be defined, and should be considered in future investigations (17
). Alternatively, frailty may actually operate as a marker of delirium, or vice versa
. Although the criteria proposed by Fried et al
. remains the most widely used construct (4
), there is controversy as to whether other common age-related conditions such as cognitive impairment should be included in the definition of the syndrome (19
). Another important consideration is whether frailty is dynamic and potentially reversible. Considering that half of the patients in our study were pre-frail, whether interventions would reduce the development of frailty is clinically relevant.
We focused on measuring delirium in the early postoperative period; as a result, incidents of later onset delirium may have been missed. Second, our study sample size is relatively small and the results should be confirmed by a larger study.
In summary, including frailty assessment in the preoperative setting may improve preoperative risk assessment of older patients, particularly in identifying the patients at risk for postoperative delirium. Furthermore, expanding frailty research to the surgical setting may also advance our understanding of the pathophysiology of postoperative delirium.