We compared the clinical characteristics of premature CHD with mature CHD patients and explored the risk factors for the vascular disease severity in premature and mature CHD. Our results showed that female patients in the premature group had a higher rate of dyslipidaemia than those in the mature group, and the TyG index was also not a useful marker for premature CHD. When including the TyG index only, female patients with MVD and male patients with mature MVD were more likely to have higher levels than those with premature SVD. Additionally, significantly higher rates of hypertension, diabetes, OMI, smoking (female), obesity (male), and higher levels of Lp(a) and CRP (female) were observed in patients with MVD, considering traditional risk factors and other clinical indicators.
One important finding was that the differences in most characteristics between premature and mature CHD patients were not statistically significant. Also, among the few statistically significant risk factors, the proportions and levels were higher in mature patients than in premature patients. Only dyslipidaemia was found the opposite trend for female patients. Several previous studies have explored the association between risk factors and onset age of CHD. Our finding is similar to that of Mohammad et al. who found that premature CHD patients had higher rates of hyperlipidaemia and family history of CHD than mature patients . However, this is inconsistent with the results of Zhou et al., who found that the rates of family history of hypertension, diabetes and the levels of BMI, TG, TC and LDL-C in the premature CHD group were higher than those in the mature group . Both studies found more patients with MVD among the mature CHD group than in the premature group, which was not observed in our study [6, 14]. One explanation for the divergence in the results is that the studies enrolled different populations and sample sizes. In addition, our study added stratified analyses by gender and included new risk factors for CHD, such as TyG index, Lp(a), CRP, and Cre for multivariate analysis. All of the above may contribute to the discrepancies seen with the previous study.
The higher rate of hypertension and higher levels of Lp(a), Cre, and TyG index in mature CHD may be explained by the fact that the prevalence of hypertension as well as the level of Lp(a), Cre, and TyG index rose with elevated age [4, 29–31] The onset of CHD in women comes later than in men by 7–10 years because of the role of endogenous estrogen in enhancing vascular relaxation and improving blood lipids and blood coagulation [32, 33]. However, CHD mortality is higher in women than in men because of this late onset . This study observed a higher incidence of dyslipidaemia in premature CHD female patients, which is consistent with the findings of Penida et al . This reveals that general practitioners and clinicians should pay more attention to the early prevention of dyslipidaemia in women at a young age, and patients with dyslipidaemia should regularly participate in cardiovascular disease screening.
IR is defined as a sensitivity reduction in insulin-dependent cells’ response to insulin . It induces an imbalance in glucose metabolism and leads to dyslipidaemia and lipid triad, which each contribute to CVD and atherosclerotic plaque generation . The TyG index proposed by Simental-Mendia et al. could be useful as a simple and reliable surrogate to measure IR in clinical practice . Compared with traditional indices for predicting IR, HOMA-IR, the TyG index is easier to obtain and has higher sensitivity [18, 21, 28]. Also, Kim et al., Park et al., and Su et al. identified that an increased TyG index is associated with a raised risk of CHD [18, 20, 38]. In our study, no difference was found in the TyG index between the premature and mature CHD groups in univariate analyses, while the multivariate analyses showed that more male patients with premature CHD had a lower level of TyG index. The TyG index thus did not present superiority in predicting premature CHD. Furthermore, the TyG index was positively associated with diabetes, dyslipidaemia, Hb, obesity, and CRP, which is partly consistent with the results of Jin et al. and Wang et al. [17, 19, 21]. The main explanation for this correlation is that most of these factors are components of metabolic syndrome and IR .
In this study, the TyG Index was used as one of the markers of CHD vascular disease severity, which was reflected by whether the patients had SVD or MVD. Although it is not claimed that MVD of CHD is more severe than SVD, a published study identified that patients with MVD are more likely to experience complications with diabetes, renal insufficiency, and a history of myocardial infarction compared with those with SVD . Also, Part et al. and Lopes et al. found that MVD was associated with a worse prognosis than SVD [22, 40]. Therefore, prevention of MVD risk factors and early prediction of the number of diseased vessels could reduce the risk and burden of CHD through appropriate interventions . Our finding that patients with MVD of both premature and mature CHD generally had more patients with the highest TyG index than those with premature SVD is consistent with that of Mao et al. . The correlation between the TyG index and vascular disease severity disappeared after adjusting for traditional CHD risk factors; however, other risk factors such as hypertension, diabetes, obesity, smoking, OMI, and Lp(a) showed a positive association with vascular disease severity. This may be because the TyG index is associated with cardiometabolic risk factors, which have a stronger effect on the vascular disease severity than the TyG index in our models . This suggests that the TyG index should be added as one of the risk factors for CHD or CVD screening, and could be used as an auxiliary indicator for identifying vascular disease severity.