Association of PWV levels with AAA
All 9 eligible studies reported on the relationship of PWV levels with AAA. As quantified using I 2 and P-value, the heterogeneity across included studies was statistically significant (P< 0.00001, I 2=98.9%). Studies were weighted based on the number of patients in each study and other factors. Meta-analysis showed that patient’s PWV values were higher in patients with AAA than those in control subjects (WMD=2.36m/s, 95% CI 2.02~2.70,P<0.001) (Figure 2A). To investigate potential publication bias, the funnel plot was created for studies included in a meta-analysis of PWV (Figure 2B), with a vertical axis for study size (standard error) and horizontal axis for the standardized difference in means which averaged overall at around 2.36. Lack of significant asymmetry in the funnel plot both on the x and Y axis in Figure 2 B suggests the low likelihood of publication bias.
Subgroup analysis
Subgroup meta-analysis results are summarized in Table 2. High levels of pulse wave velocity were associated with AAA as defined by cf-PWV (WMD=0.63m/s,95% CI 0.26-1.00, P<0.00001) and infrarenal PWV (WMD=12.65m/s,95% CI11.75-13.54, P=0.004) (Figure 3B).
Subgroup analysis was also performed if it was possible to match risk factors such as age (9/9 studies), sex (7/9 studies), smoking(6/9 studies), diabetes(5/9 studies) and hypertension(5/9 studies) (Table 2).
The PWV levels were significantly lower in AAA patients than those in the control group if there was significant inter-group difference in age between AAA and control (WMD:-0.48; 95%CI:-0.94,-0.01, I2=77%, P=0.005), however, PWV levels were significantly higher in AAA patients than those in the control group if there was not significant inter-group difference in age between AAA and control (WMD:5.59; 95%CI:5.09,6.09, I2=99%, P<0.000)(Figure 3B).
The PWV levels were significantly lower in AAA patients than those in the control group if there was significant inter-group difference in hypertension between AAA and control(WMD:-0.52;95%CI:-0.99,-0.06, I2=88.8%, P=0.003), however, PWV levels were significantly higher in AAA patients than those in the control group if there was not significant inter-group difference in hypertension between AAA and control (WMD:2.05; 95%CI:1.23,2.87, I2=96.7%, P<0.000)(Figure 4A).
The PWV levels were significantly lower in AAA patients than those in the control group if there was significant inter-group difference in diabetes between AAA and control(WMD:-2.10; 95%CI:-3.23,-0.97), however, PWV levels were significantly higher in AAA patients than those in the control group if there was not significant inter-group difference in diabetes between AAA and control (WMD:0.52;95%CI:0.11,0.93, I2=95.2%, P<0.000)(Figure 4B).
The PWV levels were not significantly different in AAA patients than those in the control group if there was significant inter-group difference in sex between AAA and control(WMD:-0.20; 95%CI:-0.71,0.31), however, PWV levels were significantly higher in AAA patients than those in the control group if there was not significant inter-group difference in sex between AAA and control (WMD:4.35;95%CI:3.89, 4.80, I2=99.1%, P<0.000)(Figure 5A).
The PWV levels were significantly higher in AAA patients than those in the control group if there was significant inter-group difference in smoking between AAA and control(WMD:1.12; 95%CI:0.44,1.81), PWV levels were also significantly higher in AAA patients than those in the control group if there was not significant inter-group difference in smoking between AAA and control (WMD: 0.43 ;95%CI: -0.00, 0.87, I2=95.2%, P<0.000)(Figure 5B).