The study population comprised a total of 2970 patients in which 62.5% were males. The baseline characteristics according to tertile of β-HDBA levels were summarized in Table 1. The results showed that subjects with higher β-HDBA levels also had higher SBP, higher prevalence of diabetes, dyslipidemia and family history of premature CAD. Furthermore, with the increase of β-HDBA levels, FBG, TC and LDL-C significantly increased (P<0.001 for trend). It seems that subjects with higher β-HDBA levels were older, but it is not statistically significant. Whereas BMI, DBP, TG, HDL-C, Crea and UA levels were similar among the groups. In addition, no associations were found between β-HDBA and overweight/obesity, hypertension, history of stroke, smoking status and statins use.
Correlations of serum β-HDBA levels with the traditional CAD risk factors
Significant positive correlations were found between serum β-HDBA level and FBG (r=0.067, P<0.001), TC (r=0.070, P<0.001), and LDL-C (r=0.066, P=0.001). Serum β-HDBA level was also significantly positively correlated with age (r=0.041, P<0.05) and SBP (r=0.040, P<0.05). However, associations between β-HDBA and BMI, DBP, TG, HDL-C, Crea and UA were not significant (Table 2).
Relations of β-HDBA levels with CAD severity
In order to analyze the relationships between β-HDBA and CAD severity, patients with positive findings in coronary angiography were classified into subgroups with 1-3 and >3 stenosed regions. β-HDBA was significantly increased (Ptrend=0.016) with the increase of the number of stenosed regions. Then the CAD patients were further divided into subgroups with 1 and >1 stenosed vessles. As shown in Fig 1, no significant changes were found for β-HDBA levels among groups. As the Gensini score is widely used for evaluating of coronary atherosclerosis severity, the studied patients were further divided into different subgroups according to tertiles of the Gensini score. The results indicated that β-HDBA level was found to be associated with the Gensini scores (Ptrend=0.05).
The multivariable logistic regression analysis of β-HDBA level with CAD
To examine the independent relationship between β-HDBA and CAD severity, multivariate logistic regression analysis was performed. Here, we adopted T3/T1 of Gensini score tertiles on behalf of CAD severity. As shown in Table 3, traditional risk factors such as age, gender, smoking (both former and current smoking), hypertension, diabetes, family history of premature CAD were all positively associated with the Gensini scores, while in gender, female was a protective factor for CAD, with OR of 0.417 (0.308-0.564). In addition, we found elevated β-HDBA levels remained independently associated with T3/T1 of Gensini score tertiles (OR=1.151, 95% confidence interval:1.012-1.309, p =0.032), after adjusting for traditional risk factors including age, gender, smoking status, overweight/obesity, hypertension, dyslipidemia, diabetes, history of stroke, family history of premature CAD.
The stratified analysis of β-HDBA levels with CAD
Stratified analysis of the associations of serum β-HDBA levels (per 1-SD increment) and the severity of coronary artery lesion was conducted in different groups of age, gender, BMI, smoking status, hypertension, dyslipidemia, diabetes, history of stroke and family history of premature CAD. The interactions between β-HDBA and these factors on the distribution of CAD were analyzed. As presented in Fig. 1, there are significant associations between β-HDBA and CAD in female, non-smokers, subjects with hypertension, diabetes and family history of premature CAD. Moreover, we observed that the association between β-HDBA and CAD was modified by gender (Pinteraction = 0.015). β-HDBA was associated with CAD in female (HR: 1.429, 95% CI: 1.138-1.793, P = 0.002), but not in male (HR: 1.028, 95% CI: 0.892-1.1840, P = 0.704), after adjustment for age, BMI, smoking status, hypertension, dyslipidemia, diabetes, history of stroke, family history of premature CAD. However, no interaction was observed between β-HDBA and age, BMI, smoking status, hypertension, dyslipidemia, diabetes, history of stroke and family history of premature CAD (Figure 2). Then we further analyzed the association of β-HDBA level with CAD severity in male and female respectively, according to Gensini score or the number of stenosed regions. Consistent with this, β-HDBA showed significant association with Gensini score or the number of stenosed regions in female, not male (Figure 3).