Acute aortic dissection is a critical condition marked by a rupture in the inner layer of the aortic wall. Notably, acute type B aortic dissection (aTBAD) accounts for approximately one-third of all acute aortic dissections^[1,2]. Despite the rapid progression in diagnostic and therapeutic techniques, the in-hospital mortality rate of patients with aTBAD remains high at up to 13%^[3]. In addition to conventional risk factors, such as hypertension, smoking and hyperlipidemia, aging itself confers an important risk factor for aTBAD. Computed tomography angiography (CTA) has gradually become the commonly used and primary imaging modality for diagnosing aTBAD^[4]. Previous studies have identified the aortic anatomical and morphological parameters based on three-dimensional CTA reconstruction as potential predictors of aTBAD^[5-7]. However, the effects of aging on aortic morphology have not been adequately studied.

In view of the fact that the aorta continues to expand, elongate and unfold with advancing age, findings obtained without standardizing the aortic variables for age may not be entirely justified^[8,9]. Importantly, the threshold values of aortic variables used for risk stratification of aTBAD were also different in each age stage. Moreover, it is uncertain if age is linked to alterations in the true and false lumens of the descending aorta after aTBAD.

Accordingly, the main goal of this study was to analyze the correlations between age and aortic morphological variables in patients with aTBAD and controls, and identify independent factors related to aTBAD by multivariate logistic regression analysis. Together, these findings may provide additional information for clinical evaluation and surveillance of patients with aTBAD-related morphological features.

This retrospective case-control study, conducted across multiple centers, received approval from the Ethics Committee of the First Affiliated Hospital of Zhengzhou University and the Second Xiangya Hospital of Central South University, which served as the central institutional review board for all participating centers (approval number: SQ2025-194). The study’s retrospective design allowed for the waiver of individual informed consent.

Since this was a retrospective multicenter case-control study, a formal sample size calculation was not conducted. The number of consecutive eligible patients who satisfied the predefined inclusion and exclusion criteria during the study period at the participating institutions determined the study size.

The features of participants from the aTBAD and control groups are shown in Table 1. The study included 203 patients who satisfied the inclusion and exclusion criteria, with 106 in the aTBAD group and 97 in the control group. The clinical features of the enrolled aTBAD patients, including the proportion of uncomplicated, high-risk and complicated aTBAD, were provided in Supplementary Table 2. No significant differences were found in the baseline characteristics between the two groups, with all P-values exceeding 0.05.

aTBAD is an age-related catastrophic cardiovascular condition associated with high rates of complications and mortality^[10]. Of note, aging is recognized as one of the major risk factors for the occurrence of aTBAD and may also influence other established risk factors^[11]. In addition, aortic anatomical and morphological parameters have been identified to be associated with aTBAD; however, these parameters themselves may also be subject to aging. Therefore, the effect of aging on aTBAD occurrence should not be neglected in the analysis. Herein, our main findings are as follows: (1) Age was correlated with most of the morphological parameters of ascending aorta and aortic arch in both the aTBAD and control groups; (2) Nevertheless, morphological parameters of TL and the ratio of TL to TAL were not associated with age; (3) The diameter, length and tortuosity of aortic arch and angulation of ascending aorta play independent and specific roles in the aTBAD occurrence despite their positive correlations with age. The clinical implications of the identified aortic morphological features warrant further consideration. Increased aortic diameter may reflect structural remodeling of the aortic wall, including progressive dilatation and reduced wall integrity, which are commonly observed during aortic degeneration. Aortic elongation, reflected by increased aortic length, may alter the spatial configuration of the thoracic aorta and modify the distribution of mechanical forces along the aortic wall. Similarly, increased aortic tortuosity and angulation represent geometric alterations of the aorta that may be associated with changes in local hemodynamic patterns and wall stress distribution.

Current guidelines recommend aortic diameter as the primary morphological risk factor for aortic disease, with a descending aortic diameter > 5.5 cm serving as an indication for surgical intervention^[12]. Nevertheless, studies based on the International Registry of Acute Aortic Dissection (IRAD) database have indicated that aTBAD can occur in the absence of marked aortic dilation. Specifically, 81.6% of patients with aTBAD had aortic diameters less than 5.5 cm^[13], and 21.2% had aortic diameters less than 3.5 cm^[14]. Therefore, beyond a single indicator of aortic diameter, evaluating additional aortic morphological parameters may provide a more comprehensive assessment of aortic geometric characteristics associated with aTBAD. Given the lack of pre-event imaging data and the substantial changes in descending aortic morphology after the aTBAD onset^[15], the present study paid more attention to the non-dissected proximal aorta region, where the aortic morphological variables remained relatively preserved after dissection.

Aging of both the healthy and pathological aorta is an irreversible and complex process that induces progressive structural and functional changes in the aortic wall over time^[16]. Morphological alterations of the aorta are among the most important aspects of this process. Firstly, aging leads to changes in the components of the aortic wall, including decreased elastin and increased collagen^[16-18], which reduce aortic wall compliance and may ultimately increase the risk of aortic dissection or rupture. Secondly, the aorta may elongate over time^[8,19], while the vertebral column may gradually shorten with aging^[20], resulting in alterations in aortic tortuosity and angulation. Due to the physiologic enlargement and unfolding of the aorta throughout life, it is not always justified to apply fixed threshold values to assess the risk of aTBAD. Interestingly, age showed a negative coefficient after adjustment for aortic morphological variables in the multivariable model. This finding should not be interpreted as indicating a protective effect of older age. Instead, this coefficient represents the residual association of chronological age with aTBAD after accounting for age-related morphological characteristics. Since several morphological parameters included in the model may themselves reflect age-associated aortic remodeling, adjustment for these variables may have altered the independent contribution of chronological age.

In non-dissecting population, age-related alterations in aortic morphology have been investigated relatively extensively^[8,9,21,22]. Age-associated changes in aortic geometry are accompanied by increased aortic stiffness, which is closely pertinent to the age-related unfolding of the aortic arch^[8]. Additionally, the enlargement and unfolding of the aorta are significantly accelerated in patients with hypertension^[23]. Nevertheless, the correlations between aortic morphological variables in patients with aTBAD and age have been much less studied. In this study, we uniquely analyzed the morphological variables indexed to age and found that five variables, including aortic arch diameter, length, tortuosity, ascending aorta angulation and age, were independently associated with the presence of aTBAD. Moreover, in the non-aortic disease control group, the ascending aortic diameter showed a trend toward enlargement with increasing age (approximately 1 mm per decade), although this association did not reach statistical significance (P = 0.082). In contrast, the increase in ascending aortic length was statistically significant (approximately 3 mm per decade, P = 0.046), which was comparable with previous studies^[9,21,24].

Moreover, we found that morphological variables of the TL were not correlated with age, even after normalization to TAL, which contradicted previous reports^[25]. One possible explanation is that our study included cases with false lumen involvement extending to the abdominal aorta. In addition, false lumen size could be affected by poor control of blood pressure, the site of intimal tear and false lumen embolization. Following dissection, the true lumen becomes compressed, and the diameter, length and volume of the total lumen in the dissected descending aorta were significantly greater than those in the control group, accompanied by steeper angulation and larger tortuosity. Monitoring dimensional changes in the true lumen and false lumen may facilitate optimized preoperative planning, assessment of branch vessel perfusion, and evaluation of aortic remodeling following thoracic endovascular aortic repair (TEVAR).

Recent advances in the concept of biological aging have highlighted that chronological age may not fully represent the functional status of individual organs and vascular systems^[26]. Similar concepts, such as vascular age, have been proposed to capture age-related changes beyond traditional chronological aging. In this context, our findings showing age-associated variations in aortic arch morphology suggest that quantitative assessment of aortic geometric characteristics may provide additional information regarding vascular aging. Although further longitudinal studies are required, these observations may contribute to the future development of an “aortic age” concept based on imaging-derived morphological features.

Nonetheless, there are several limitations in the present study that need to be acknowledged. First, due to the retrospective and case-control design, the results may not fully establish a causal relationship between aortic morphological variables and aTBAD. Second, the use of hospital-based controls rather than population-based healthy volunteers may introduce referral bias. However, this design was chosen because obtaining aortic CTA in truly healthy asymptomatic individuals is ethically and practically unfeasible. The control group in our study is comparable to those used in prior published studies investigating aortic morphology^[8,9]. Third, although BSA and gender were adjusted in the multivariable analyses to account for body size and demographic differences, residual confounding related to other unmeasured anthropometric characteristics cannot be completely excluded. Fourth, the relatively young age of our study population may limit the generalizability of our findings to older patients with aTBAD. However, the observed associations between aortic morphological characteristics and aTBAD remained significant after adjustment for age, suggesting that these morphological features may be independently related to the presence of aTBAD after accounting for chronological age. Fifth, quantitative assessment of aortic calcification was not available in the present cohort. Calcification represents an important marker of vascular aging and aortic wall degeneration, and future studies integrating calcification burden with geometric parameters may provide a more comprehensive understanding of aortic remodeling in aTBAD. Sixth, although smoking status was comparable between the two groups, residual confounding from smoking-related exposure, including smoking intensity and cumulative pack-years, cannot be completely excluded.

Increased diameter, length and tortuosity of aortic arch and angulation of ascending aorta are independently associated with aTBAD occurrence, despite these variables being positively correlated with age. These findings suggest that incorporating age-related changes in aortic morphology may aid in the identification of patients at increased risk of aTBAD. Further research is warranted to establish age-adjusted threshold values for these parameters, which could facilitate the early risk stratification of high-risk individuals and guide preventive strategies.