To the best of our knowledge, this was the first longitudinal study to investigate the changes in frailty in older patients after abdominal surgery. Patients with similar trajectories were classified into subgroups using LCGMs, and the factors influencing each trajectory were evaluated. The results showed that the patients could be classified into four frailty trajectory groups—a no frailty group, a frailty exacerbation group, a frailty improvement group, and a persistent frailty group. Frailty was either exacerbated or improved, and its trajectory was heterogeneous. Additionally, the frailty trajectory could be influenced by many factors. Compared with previous cross-sectional studies in which default frailty remained unchanged, in this study, behavior was classified according to a dynamic developmental trend.
Frailty status in older patients after major abdominal surgery
In total, 21.3% of the older patients who underwent major abdominal surgery and who were included in this study were frail before surgery, which was similar to the findings of Yang et al [26]. Patients undergoing grade III or IV abdominal surgery are in a severe condition and present with a persistent decline in multiple organ system functions. We found that, compared with the preoperative condition, patients were significantly frailer at discharge, and the overall incidence of frailty remained higher one month after surgery than before the operation. Patients are in a state of high consumption after surgery, with insufficient compensatory capacity and weakened immunity. Frailty is more likely to occur under the stimulation of therapeutic procedures and in a hospital environment. However, with the clinical application of “Enhanced Recovery After Surgery” (ERAS) programs, postoperative hospital stay is shortened, and medical care services are greatly reduced after discharge [27]. Patients lack disease-related knowledge and self-management ability, which also aggravates the development of frailty. Determination of the frailty status is an important preoperative risk assessment for older patients.
The frailty trajectory in older patients after major abdominal surgery
In this study, we fitted four frailty trajectories for older patients after major abdominal surgery and used them to categorize patients into a no frailty group, a frailty exacerbation group, a frailty improvement group, and a persistent frailty group, thus providing further evidence for heterogeneity in frailty development. The proportion of patients in the frailty exacerbation and persistent frailty groups was relatively high, likely because older surgical patients are at greater risk of disease, their physiological functions deteriorate, their independence may be lost, and their negative emotions may increase. Additionally, postoperatively, the bodies of older patients are stimulated by inflammatory reactions and immune system disorders, as well as activity restrictions, the effects of drugs, environment, and role changes, which often aggravate their frailty [28]. Patients in these groups need long-term follow-up and continuous care. In addition, we found that frailty may exhibit a trend of “improvement”. Some patients have strong stress-enduring ability and a good tolerance to surgical treatment, and may also have access to early postoperative rehabilitation exercise, which improves the original frail state or even reverts it to a no-frailty state. However, owing to the limitation of follow-up time in our study, the changes in frailty status were not pronounced, a shortcoming that should be addressed in future studies. The development of a frailty curve provides possibilities for the prevention, delay, and reversal of this process. Focusing on individual characteristics is conducive to attenuating frailty and providing a basis for the formulation and effective implementation of frailty intervention plans.
Factors influencing frailty trajectories in older patients after major abdominal surgery
Risk factors for frailty trajectory exacerbation
The results of this study showed that abnormal BMI, comorbidity, grade IV surgery, intraoperative abdominal drainage tube indwelling time, postoperative complications, and anxiety may be risk factors for frailty exacerbation in patients. An abnormal BMI, associated with malnutrition and obesity, increases the risk of frailty. On the one hand, patients who undergo abdominal surgery often have digestive problems and experience perioperative fasting, resulting in inadequate energy and protein intake, which increases the risk of frailty; on the other hand, patients with a high BMI have more adipose tissue, and, consequently, secrete greater amounts of adiponectin, IL-6, and tumor necrosis factor, resulting in metabolic disorders and a decrease in skeletal muscle mass, rendering these patients more prone to frailty [29-30]. Frailty and comorbidity have a bidirectional relationship. Chronic inflammation, immunity impairment, and abnormal neuroendocrine regulation can enhance frailty in patients with comorbidities, while frail patients with persistent dysfunction are more susceptible to other diseases.Wu et al. [31] investigated whether a correlation exists between frailty and the number of comorbidities; however, the results of that study were not conclusive. In addition, although frailty susceptibility can increase with age, evidence supports that frailty is the result of the cumulative effect of physiology and environment, and the value of age as a sensitive indicator of frailty is limited [32].
We found that patients who underwent stage IV surgery (partial gastrectomy, pancreatic necrosectomy) fell mostly into the persistent frailty or frailty exacerbation categories. It may be that the deep location, large scope, and intraoperative bleeding of such surgery significantly increase the risk of frailty. Preoperative frailty is an independent predictor of postoperative complications [33], little is known regarding the effect of postoperative complications on frailty.The Clavien–Dindo complication classification system was used to evaluate the incidence of postoperative new-onset frailty [34]. It was found that patients with grade II or higher complications had a higher rate of new-onset frailty and this frailty was longer-lasting. Postoperative complications increase the body’s vulnerability and system dysfunction aggravates the original weakness. Abdominal drainage has unique advantages in the assessment and prevention of postoperative complications such as gastrointestinal fistula formation, infection, and hemorrhage. However, Harvey et al. indicated that catheter-related complications, unplanned extubation, and a lack of nursing experience related to drainage would inevitably harm patients [35]. We also found that the frailty of patients was closely related to the duration of drainage tube placement, which may be associated with the effect of drainage on postoperative rehabilitation exercise and the anxiety level of patients. Anxiety is the main negative emotion observed in hospitalized patients. Patients focus too much on somatic symptoms and have low enthusiasm for and compliance with treatment and rehabilitation exercise, which increases the risk of progressing to a state of aggravated or persistent frailty [36].
4.3.2 Protective factors for frailty trajectories
We believe that a high level of education represents a protective factor for frailty, while ERAS-based management (early mobilization and early feeding) can help to alleviate and even reverse postoperative frailty. Patients with higher educational attainment generally have a higher level of health literacy and are more willing and better able to manage themselves. “Early ambulation and early oral feeding” underlies ERAS protocols. Postoperative patients have limited activities and, consequently, their muscle reserves decline [37]. Early activities can promote the recovery of respiratory, gastrointestinal, and musculoskeletal functions; prevent postoperative complications; and improve frailty. Therefore, it is recommended that patients are placed semi-reclining in bed or perform moderate in-bed activities after awakening; they should also undertake out-of-bed activities one day after surgery, and subsequently increase the amount of activity they perform day by day. ERAS guidelines state that the early recovery of oral feeding after surgery can promote intestinal motility and intestinal mucosal recovery as well as prevent intestinal flora imbalance and bowel displacement [38]. Clinical recommendations include “the recovery of oral feeding without waiting for intestinal ventilation” and “the recovery of oral feeding according to the patient’s wishes after surgery”. We found that patients who underwent grade III surgery had stable preoperative function and strong stress-countering ability; surgery effectively relieved the pain, and the postoperative frailty could be improved or even reversed.