IDH patients exhibited significantly higher TC, TG, LDL, Apo B, Lp(a) and Apo B/Apo AI levels
The serum concentrations of TC, TG, LDL-C, HDL-C, Apo AI, Apo B and Lp(a) were measured in all patients (Fig. 2). In Group 1 (IDH), the concentration levels of TG, total TC, LDL-C, HDL-C, Apo B and Lp(a) were 1.63 ± 1.26 mmol/L, 4.50 ± 1.48 mmol/L, 2.67 ± 0.9 mmol/L, 1.16 ± 0.29 mmol/L, 0.80 ± 0.22 g/L and 25.35 ± 24.01 mg/dl, respectively. In Group 2 (control group), the concentration levels of TC, TG, LDL-C, HDL-C, Apo AI, Apo B and Lp(a) were 4.23 ± 2.18 mmol/L, 1.4 ± 0.91 mmol/L, 2.52 ± 0.83 mmol/L,1.21 ± 0.36 mmol/L, 0.76 ± 0.23 g/L and 22.45 ± 21.11 mg/dl, respectively. The patients with symptomatic IDH indicated significantly higher levels of TG (P = 0.002), TC (P = 0.00), LDL-C(P = 0.00), Apo B (P = 0.00), Lp(a)(P = 0.006). No statistically significant differences were noted for the HDL-C (P = 0.125) and Apo AI (P = 0.326). The ratios of Apo B/Apo AI were higher in the symptomatic IDH comparing with control group (0.78 ± 0.33 versus 0.71 ± 0.25, P < 0.01).
The percentage of high-TC, high-TG, high-LDL, high-Apo B and high-Lp(a) were significantly increased in the IDH group
The percentage of dyslipidemia incidence in the control and IDH group were further investigated in our study. The incidence of the high TC, high TG, high-LDL-C, low-HDL-C, Apo AI, Apo B and Lp(a) were 31.19%, 13.85%, 20.17%, 7.52%,14.9%, 30.8% and 28.9%, respectively, compared to 23.33%, 15.34%, 14.8%, 5.98%, 13.6%, 21.76% and 51.4% that was noted in the control group, respectively (Table 3). The incidence of the high- TC, high-TG and high-LDL-C, Apo B and Lp(a) were significantly higher in the IDH group compared with the control group (P = 0.000, P = 0.00, P = 0.02, P = 0.000, P = 0.000 respectively). No statistically significant differences were noted with regard to HDL-C (P = 0.189) and Apo AI (P = 0.412).
The association between serum lipid abnormalities and the degree of IVDD
To further investigate correlation for the incidence of a symptomatic IDH with an elevated LDL-C, TC, TG, Lp(a), Apo B and Apo B/Apo AI, the correlation analysis was conducted between serum lipid abnormalities and the degree of IVDD (Pfirrmann grade). As shown in Fig. 3, the correlation between elevated LDL-C, TC, TG, Apo B, Lp(a) and incidence of IDH were significant (R2LDL = 0.017, P < 0.001; R2TC = 0.004, P < 0.004; R2TG = 0.015, P < 0.001; R2Apo B = 0.004, P < 0.001; R2 LP(a) = 0.021, P < 0.008). These results suggested that patients with higher LDL-C, TC, TG, Lp(a), Apo B and Apo B/Apo AI levels are closely related with disc herniation.
Hyperlipidaemia did not affect the degenerated segment of the intervertebral disc
The categorical data of the patients with disc herniation were analyzed in order to examine the associations between hyperlipidaemia and the disc segment in the intervertebral disc group. The hyperlipidaemia group (n = 689) exhibited the following percentages of degenerated segments in the cervical, thoracic and lumbar regions: 13.9%, 1.3% and 84.8%, respectively. In contrast to the hyperlipidemic samples, the normal serum lipids group exhibited incidences of 18.8%, 1.3% and 79.9% that corresponded to the cervical, thoracic and lumbar regions, respectively (n = 229). No significant differences in the herniation segments were noted between these two groups (p = 0.201) (Fig. 4).
The categorical data were further analyzed in order to identify the association between the serum lipid levels and the segment of disc herniation in the cervical and lumbar regions. Considering the small sample of affected segment in the thoracic disc herniation, we only analyzed the serum lipid levels and segment of disc herniation in the cervical and lumbar regions.
The values of the total segment in the cervical, thoracic and lumbar regions were 137, 12 and 769 respectively. No significant differences were noted between serum lipid levels in the C3-C4 (P = 0.282) and C5-6 (P = 0.373) segments with regard to TC levels (Fig. 5A). Similarly, no significant differences were observed in the C3-C4 (P = 0.108) and C5-6 segments with regard to LDL-C levels (P = 0.254) (Fig. 5C). With regard to the levels of Apo B, the C5-6 segment in the hyperlipidaemia group (31.9%) was higher than that of the normal group (24.2%), although no significant differences were noted (Fig. 5D, P = 0.2). With regard to the levels of ApoA (Fig. 5E), Lp(a) (Fig. 5F) and triglycerides (TG) (Fig. 5B), the distribution herniation segment in the hyperlipidaemia and control groups exhibited similar trends both in the lumbar and cervical segments. However, we do not get the significance statistic in our study. Comparing with cervical and lumbar IDH, the incident of thoracic IDH is quite low. The relatively small sample size in our study may contribute to the no-significance result.
Patients with elevated LDL-C, TC, TG, Lp(a), Apo B and Apo B/Apo AI levels exhibited a higher risk of disc herniation
To further identify risk for the incidence of a symptomatic IDH with an elevated LDL-C, TC, TG, Lp(a), Apo B and Apo B/Apo AI, multivariate logistic regression analysis was performed. As shown in Table 4, the odds ratios (ORs) for the incidence of a symptomatic IDH with an elevated LDL-C, TC, TG, Lp(a), Apo B and Apo B/Apo AI were 1.583 (CI, 1.427–1.796), 1.74(CI, 1.282–2.365), 1.62 (CI, 1.295–2.023), 1.58(CI, 1.255–1.975), 1.49 (CI, 1.346–1.661) and 1.39(CI, 1.254–1.595), respectively (P < 0.01). These results suggested that patients with higher LDL-C, TC, TG, Lp(a), Apo B and Apo B/Apo AI levels exhibited a higher risk of disc herniation.