According to this study, the MetS components could significantly predict the incidence of poor outcomes in patients with ATAAD after surgery during 3 years follow-up by multivariable and subgroup analyses. After adjusting for confounding factors, MetS were independent risk factors for adverse events, which might also be a risk factor for aortic dissection. Among the MetS components, BMI was the strongest predictor of poor outcomes, and the scoring system showed good predictive power.

MetS had five components, BMI, blood pressure, FPG, HDL and TG [10]. As a Complex and common disease, it is associated with insulin resistance, visceral adiposity, dyslipidemia, and hypertension, which are risk factors for cardiovascular diseases [11]. When patients met multiple criteria and were diagnosed with MetS, the risk was higher than that of isolated MetS. In the final common pathway, a series of inflammatory signaling cascades are triggered, leading to clinical manifestations [12].

Obesity, a risk factor for cardiovascular disease, affects multiple systems, including the respiratory and urinary systems [13]. In addition, previous studies have found that BMI was an independent risk factor for major in-hospital adverse outcomes in patients with ATAAD after surgery and preoperative hypoxemia before surgery [14, 15]. Lio et al. found that ATAAD patients with A BMI ≥ 30 kg/m2 had higher operative mortality rates and an increased risk of low cardiac output syndrome, pulmonary complications, and other postoperative morbidities [16]. The possible reason for these findings is that obesity is strongly linked to insulin resistance, increased adipokine production, and chronic low-grade inflammation. Adipose tissue releases pro-inflammatory cytokines such as TNF-α and IL-6, which contribute to vascular remodeling, endothelial dysfunction, and aortic stiffness.In our study, BMI was also the strongest predictor of poor outcomes during the 3-year follow-up by the MetS component analysis.

Glucose metabolism, which expands fatty acid oxidation, insulin resistance, and an imbalance of hormones and inflammatory cytokines, could contribute to the incidence of adverse events [17]. Hyperglycemia promotes endothelial dysfunction through oxidative stress and advanced glycation end-products. These processes lead to vascular rigidity and increased susceptibility to dissection and complications. However, the effect of the prognosis of acute aortic dissection on blood glucose levels remains controversial. A previous study reported that T2DM could reduce clinical complications and mortality in Stanford type B aortic dissection after thoracic endovascular aortic repair during a 3-year follow up [18]. One possible reason is that the anti-aneurysm effect of metformin is not achieved by lowering the blood glucose level but is related to its anti-inflammatory effect, the reduction of inflammatory cell infiltration into the aortic wall and its protective effect against aortic smooth muscle cell injury. Lin et al. found that glucose variability is associated with the incidence of postoperative delirium in patients with acute aortic dissection [19]. Numerous studies have found that nearly 70% of AD patients suffer from hypertension, and T2DM has been demonstrated to be closely related to the occurrence of hypertension. Collectively, as a MetS component, elevated blood glucose or T2DM was an independent risk factor of ATAAD prognosis after surgery. We speculate that the effect of insulin resistance was expanded by the synergism of other MetS components, which triggered a common signal. In addition, elevated blood glucose levels and T2DM play important roles in multiple organs and systems involved in the long-term outcomes of ATAAT after surgery. There may be a factor that is not yet known in the complex microenvironment of T2DM, and basic research should be performed in the future to elucidate the underlying mechanisms.

Hypertension is a common cause of aortic dissection, and high blood pressure leads to increased shear stress on the aortic wall, aggravating hematoma expansion and expands the false lumen. Concomitantly, hypertension can influence the Renin-Angiotensin-Aldosterone System, sympathetic sensory system incitement, and cytokine levels to increase inflammation and promote vascular smooth muscle cell hypertrophy, which not only drives the acute dissection process but also worsens postoperative outcomes [20]. Bossone et al. reported a J-curve association between SBP and in-hospital mortality in patients with acute aortic dissection [21]. Therefore, blood pressure control is the main treatment for ATAAD, which can also alleviate chest pain [22]. Our results also support previous publications showing that blood pressure is an important predictor of adverse outcomes.

Dyslipidemia exacerbates aortic wall degeneration, leading to a higher risk of dissection progression and postoperative complications. With direct effects on the inflammatory response, TG is involved in oxidative stress and aortic stiffness [23]. HDL, as a protective particle, plays a crucial role in reverse cholesterol transport and exerts protective effects against inflammation, oxidation, angiogenesis, and glucose homeostasis [24]. Lin et al. found that a high TG/HDL cholesterol ratio is a risk factor for in-hospital mortality in patients with type B acute aortic dissection [4]. In our study, we found that reduced HDL levels were an independent risk factor for poor outcomes, after adjusting for potential confounding variables. However, the function of TG is not robust.

To date, there are several MetS diagnostic criteria, such as the National Cholesterol Education Program criteria (NCEP), International Diabetes Federation (IDF), and American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI). Research has shown that the NCEP MetS definition may be more suitable for the Chinese population. A recent study demonstrated that compared to the AHA/NHLBI and IDF criteria, the prevalence of cardiovascular disease was more evident when MetS were defined according to the NCEP criteria (OR:1.40) [25]. Therefore, we selected the NCEP criteria for this study.

Our study has some limitations. First, this was a single-center study with a small number of enrolled patients, which may have introduced selection bias. Future studies including multiple centers or employing more randomized sampling methods should be performed to mitigate this bias. Second, the underlying mechanistic link between MetS and adverse events is unclear as potential risks may affect the incidence of poor outcomes. Animal model studies and prospective clinical observations will perform to explore deeper relationship. Third, while the statistical methods used, such as multivariable Cox regression, are appropriate, but with limitations, such as the potential for overfitting or the assumptions underlying these methods. Lastly, due to the inclusion of patients with ATAAD undergoing surgery only, our conclusions might not be applicable to patients with aortic dissection undergoing conservative treatment.