Many studies indicate that CD may cause skeletal muscle loss or sarcopenia[22, 24, 25]. However, the prevalence of sarcopenia among patients with CD varies significantly in relevant studies. Schneider et al. discovered that the prevalence of sarcopenia is high at 60% among remission phase CD patients through measurements obtained via dual-energy X-ray absorptiometry (DEXA)[21]. Zhang et al. obtained a prevalence rate of 61.4% in 114 CD patients in China through the measurement of the skeletal muscle area via abdominal CT with SMI of less than 55 cm2/m2 in male and SMI of less than 39 cm2/m2 in female patients[20]. A US study in Iowa calculated the total psoas index via CT among IBD patients and derived a 24.7% prevalence rate of sarcopenia[25].
In this study, we found a sarcopenia prevalence of 27.4% based on the threshold set by Martin et al., who reported an SMI of less than 41 cm2/m2 in females and an SMI of less than 43 cm2/m2 (BMI < 25kg/m2) or SMI of less than 53 cm2/m2 (BMI ≥ 25 kg/m2) in males. The prevalence in this study is within the range in other literature but relatively low[20–22, 26, 27]. On one hand, this is because the measurement methods in various studies differed either due to DEXA being affected by fat tissue and body water or the different SMI thresholds used. On the other hand, the majority of the patients in this study underwent elective surgery and have thus been receiving total or partial enteral nutrition support, which might lead to the reduced prevalence of sarcopenia. We also discovered that 14.7% of sarcopenia patients in the study were of normal weight or overweight. Therefore, they are not identified as malnourished under the traditional body mass index (BMI) method. The diagnosis of sarcopenia is important to patients’ nutrition evaluation and treatment, and even normal-weight and overweight patients deserve special attention.
A few studies have indicated that the incidence of sarcopenia can cause multiple adverse events, such as osteoporosis with pathologic fracture, repeated hospitalization, mobility difficulty, and reduction in the quality of life[11–13, 25]. Chen et al. diagnosed 11.8% of 313 gastric cancer patients with post-laparoscopic gastrectomy as sarcopenic[28]. Sarcopenia significantly increased the postoperative complications, hospital stay days, and total financial costs of the patients with sarcopenia compared with the patients without it[26, 29].
Reports on postoperative complications among CD patients are scarce. Therefore, the 124 postoperative patients were studied using logistic single-factor regression and multiple-factor regression, which revealed that only sarcopenia (OR = 3.974, P = 0.027) and male gender (OR = 4.080, P = 0.024) can be considered independent risk factors for postoperative complications. SMI can reflect patients’ nutrition status and predict the incidence of complications more accurately compared with conventional nutrition indicators, such as BMI, pre-albumin level, and albumin level[9, 11, 30]. Therefore, improving patients’ perioperative nutrition status is important in reducing the occurrence of sarcopenia and postoperative complications.
Research has shown that elevation of serum cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin 6, reduces insulin-like growth factor-1 (IGF-1) in the serum and muscle of CD patients. This reduction, in turn, results in growth hormone resistance in the liver and skeletal muscle, leading to a downward moderation of the mTOR pathway into activation of the ubiquitin ligand and expression of proteolytic enzyme, which cause skeletal muscle mass reduction and impairment of muscle contraction[13, 14]. Current interventions for sarcopenia include exercise therapy, nutrition therapy, and medication. Most experts recommend that CD patients undergo exercise therapy for 6 weeks to 3 months to improve the patients’ general condition, increase the oxygenation index, and correct malnutrition[3, 10]. The guidelines of the European Society for Clinical Nutrition and Metabolism recommend that active [adult] IBD patients increase their protein intake to 1.2–1.5 g/kg/d (with 50% high-quality protein) higher than that recommended for the general population to increase the skeletal muscle cell volume, inhibit proteolysis, and reverse muscle mass reduction and functionality decline[31]. Medication for sarcopenia is still in the exploration phase, and no specific drug has been invented yet. However, Subramaniam et al. proved that a TNF-α inhibitor, infliximab, can inhibit the activation of NF-κB, reduce proteolysis and sarcolysis, and accelerate muscle formation to reverse sarcopenia[32]. Thus, gastroenterologists, surgeons, radiologists, and nutritionists should work closely together to determine an early intervention plan and a proper operation timing to reduce the incidence of postoperative complications.
However, the current study has several potential limitations. First, selection bias may exist in this retrospective work. Second, the lack of consensus regarding the adoption of an SMI threshold remains unaddressed. This study used the widely applied CT measurement method proposed by Martin et al., so it cannot be compared directly with other studies. Third, this retrospective study’s diagnosis of sarcopenia consisted of skeletal muscle mass reduction and muscle strength decline, which requires the measurement of grip strength and walking pace. These measurements could be performed in any further prospective study to achieve an accurate diagnosis of sarcopenia. Despite these limitations, this study revealed that sarcopenia can be used as an independent risk factor to predict the incidence of complications in patients with CD.