Participants’ baseline characteristics
For the data analysis, a total of 839 residents were ultimately enrolled in this study (Additional file 1: Figure S1 for a flow chart). We show these participants’ baseline characteristics in Table 1 according to tertiles of the non-HDLc/HDLc. Generally, all selected participants had an average age of 63.6 ± 9.9 years old. Males accounted for 54.2% of the subjects, and carotid plaques were identified in 341 (40.6%) of the 839 high stroke risk participants. The current sample size of 839 subjects with 341 cases had 80% power to detect at least an odds ratio of the non-HDLc/HDLc on carotid plaques at a two-tailed p value of < 0.05. The average value of the non-HDLc/HDLc was 2.88 ± 1.05. Participants in the highest tertile group of the non-HDLc/HDLc (T3) were more likely to be male and had higher values of FBG, TG, TC, and LDLc, and higher education levels, and higher proportion of smoking and carotid plaques than those in the other groups. The opposite patterns were observed for age, HDLc and the proportion of urban regions. No statistically significant differences were detected in BMI, SBP, DBP, HCY, employment status, overweight, exercise status, family history of stroke, history of stroke and TIA, hypertension, type 2 diabetes, heart diseases, elevated HCY or current antilipidaemic medication among the different non-HDLc/HDLc groups (all P values > 0.05).
Table 1
Baseline characteristics of participants
| non-HDLc/HDLc (tertile) | P |
Characteristic | T1 (n = 287) | T2 (n = 286) | T3 (n = 266) |
Male | 137 (47.7) | 148 (51.8) | 170 (63.9) | < 0.001 |
Age (years) | 64.8 ± 10.0 | 63.2 ± 9.4 | 62.7 ± 10.2 | < 0.001 |
BMI (kg/m2) | 25.54 ± 3.63 | 25.81 ± 2.99 | 26.05 ± 3.20 | 0.200 |
SBP (mmHg) | 140.08 ± 15.55 | 140.91 ± 13.34 | 139.80 ± 16.01 | 0.663 |
DBP (mmHg) | 86.87 ± 9.17 | 87.99 ± 8.78 | 87.38 ± 9.62 | 0.350 |
FBG (mmol/L) | 6.27 ± 1.87 | 6.41 ± 2.03 | 6.84 ± 2.48 | 0.006 |
TG (mmol/L) | 1.13 (0.84–1.42) | 1.54 (1.19-2.00) | 2.25 (1.60-3.00) | < 0.001 |
TC (mmol/L) | 4.27 ± 0.82 | 4.78 ± 0.78 | 5.22 ± 0.92 | < 0.001 |
LDLc (mmol/L) | 2.14 ± 0.58 | 2.70 ± 0.67 | 2.93 ± 0.81 | < 0.001 |
HDLc (mmol/L) | 1.56 ± 0.35 | 1.25 ± 0.22 | 1.03 ± 0.19 | < 0.001 |
non-HDLc (mmol/L) | 2.71 ± 0.64 | 3.53 ± 0.59 | 4.19 ± 0.78 | < 0.001 |
non-HDLc/HDLc | 1.78 ± 0.41 | 2.84 ± 0.29 | 4.10 ± 0.61 | < 0.001 |
HCY (µmol/L) | 9.0 (6.0–13.0) | 9.5 (7.0-12.4) | 9.3 (6.5–13.0) | 0.422 |
Urban | 179 (62.4) | 147 (51.4) | 102 (38.4) | < 0.001 |
Education | | | | 0.005 |
Primary school or under | 125 (43.6) | 101 (35.3) | 81 (30.5) | |
Middle or high school | 132 (45.9) | 157 (54.9) | 152 (57.1) | |
College and above | 14 (4.9) | 18 (6.3) | 26 (9.8) | |
Not reported | 16 (5.6) | 10 (3.5) | 7 (2.6) | |
Employment status | | | | 0.050 |
Unemployed | 81 (28.2) | 95 (33.2) | 107 (40.2) | |
Employed | 169 (58.9) | 158 (55.3) | 135 (50.8) | |
Not reported | 37 (12.9) | 33 (11.5) | 24 (9.0) | |
Overweight | 131 (45.6) | 132 (46.2) | 137 (51.5) | 0.316 |
Smoking | 96 (33.5) | 117 (40.9) | 129 (48.5) | 0.002 |
Lack of exercise | 156 (54.4) | 163 (57.0) | 143 (53.8) | 0.715 |
Family history of stroke | 60 (20.9) | 62 (21.7) | 54 (20.3) | 0.924 |
History of stroke | 67 (23.3) | 60 (21.0) | 49 (18.4) | 0.364 |
History of TIA | 13 (4.5) | 17 (5.9) | 9 (3.4) | 0.358 |
Heart diseases | 79 (27.5) | 65 (22.7) | 60 (22.6) | 0.294 |
Hypertension | 260 (90.6) | 248 (86.7) | 227 (85.3) | 0.148 |
Type 2 diabetes | 81 (28.2) | 83 (29.0) | 92 (34.6) | 0.213 |
Current antilipidaemic medication | 31 (10.8) | 26 (9.1) | 32 (12.0) | 0.529 |
High HCY | 42 (14.6) | 39 (13.6) | 50 (18.8) | 0.212 |
Carotid plaques | 108 (37.6) | 108 (37.8) | 125 (47.0) | 0.039 |
T1, non-HDLc/HDLc: 0.41–2.35; T2, non-HDLc/HDLc: 2.36–3.36; T3, non-HDLc/HDLc: 3.37–5.98. Continuous data are shown as the mean ± standard deviation or median (interquartile), and categorical data are shown as n (%). |
BMI body mass index, SBP systolic pressure, DBP diastolic pressure, FBG fasting blood glucose, TG triglyceride, TC total cholesterol, LDLc low-density lipoprotein cholesterol, HDLc high-density lipoprotein cholesterol, non-HDLc non-high-density lipoprotein cholesterol, HCY homocysteine |
Univariate Analysis Of Carotid Plaques
By univariate binary logistic regression with carotid plaques as the dependent variable, shown in Table 2, we found that male sex (OR 1.50, 95%CI 1.13–1.98 vs female), age (OR 1.07, 95%CI 1.05–1.09), SBP (OR 1.02, 95%CI 1.01–1.03), DBP (OR 1.02, 95%CI 1.00-1.03), FBG (OR 1.07, 95%CI 1.00-1.14), TC (OR 1.33, 95%CI 1.14–1.54), LDLc (OR 1.45, 95%CI 1.20–1.75), non-HDLc (OR 1.36, 95%CI 1.16–1.59), the non-HDLc/HDLc (OR 1.23, 95%CI 1.07–1.40), HCY (OR 1.06, 95%CI 1.04–1.09), rural region (OR 1.46, 95%CI 1.10–1.92 vs urban region), smoking (OR 1.57, 95%CI 1.18–2.07 vs ref), history of stroke (OR 1.67, 95%CI 1.19–2.33 vs ref), hypertension (OR 2.13, 95%CI 1.34–3.38 vs ref), and elevated HCY (OR 2.40, 95%CI 1.64–3.51 vs ref) were positively correlated with carotid plaques. In contrast, we observed that lack of exercise was negatively correlated with carotid plaques (OR 0.70, 95%CI 0.53–0.93 vs ref). Additionally, BMI, TG, HDLc, education, employment status, overweight, stroke family history, TIA, heart diseases, type 2 diabetes and current antilipidaemic medication were not significantly associated with carotid plaques.
Table 2
Univariate analysis of carotid plaques
Variables | Statistics | OR (95%CI) | P |
Sex | | | |
Female | 384 (45.8) | Ref | |
Male | 455 (54.2) | 1.50 (1.13, 1.98) | 0.005 |
Age (years) | 63.6 ± 9.9 | 1.07 (1.05, 1.09) | < 0.001 |
BMI (kg/m2) | 25.79 ± 3.29 | 0.97 (0.93, 1.01) | 0.132 |
SBP (mmHg) | 140.27 ± 14.98 | 1.02 (1.01, 1.03) | < 0.001 |
DBP (mmHg) | 87.41 ± 9.19 | 1.02 (1.00, 1.03) | 0.033 |
FBG (mmol/L) | 6.50 ± 2.15 | 1.07 (1.00, 1.14) | 0.035 |
TG (mmol/L) | 1.53 (1.12–2.18) | 0.95 (0.86, 1.05) | 0.339 |
TC (mmol/L) | 4.74 ± 0.92 | 1.33 (1.14, 1.54) | < 0.001 |
LDLc (mmol/L) | 2.58 ± 0.76 | 1.45 (1.20, 1.75) | < 0.001 |
HDLc (mmol/L) | 1.29 ± 0.34 | 0.93 (0.62, 1.40) | 0.730 |
non-HDLc (mmol/L) | 3.46 ± 0.90 | 1.36 (1.16, 1.59) | < 0.001 |
non-HDLc/HDLc | 2.88 ± 1.05 | 1.23 (1.07, 1.40) | 0.003 |
HCY (µmol/L) | 9.0 (6.0–13.0) | 1.06 (1.04, 1.09) | < 0.001 |
Region | | | |
Urban | 428 (51.0) | Ref | |
Rural | 411 (49.0) | 1.46 (1.10, 1.92) | 0.008 |
Education | | | |
Primary school or under | 307 (36.6) | Ref | |
Middle or high school | 441 (52.6) | 0.78 (0.58, 1.04) | 0.094 |
College and above | 58 (6.9) | 1.11 (0.63, 1.95) | 0.717 |
Not reported | 33 (3.9) | 0.73 (0.35, 1.53) | 0.403 |
Employment status | | | |
Unemployed | 283 (33.7) | Ref | |
Employed | 462 (55.1) | 1.03 (0.76, 1.39) | 0.866 |
Not reported | 94 (11.2) | 1.01 (0.63, 1.62) | 0.981 |
Overweight | | | |
No | 439 (52.3) | Ref | |
Yes | 400 (47.7) | 0.83 (0.63, 1.09) | 0.178 |
Lack of exercise | | | |
No | 377 (44.9) | Ref | |
Yes | 462 (55.1) | 0.70 (0.53, 0.93) | 0.012 |
Smoking | | | |
No | 497 (59.2) | Ref | |
Yes | 342 (40.8) | 1.57 (1.18, 2.07) | 0.002 |
Family history of stroke | | | |
No | 663 (79.0) | Ref | |
Yes | 176 (21.0) | 1.08 (0.77, 1.51) | 0.670 |
History of stroke | | | |
No | 663 (79.0) | Ref | |
Yes | 176 (21.0) | 1.67 (1.19, 2.33) | 0.003 |
History of TIA | | | |
No | 800 (95.4) | Ref | |
Yes | 39 (4.7) | 1.41 (0.74, 2.68) | 0.295 |
Heart diseases | | | |
No | 635 (75.7) | Ref | |
Yes | 204 (24.3) | 1.21 (0.88, 1.66) | 0.246 |
Hypertension | | | |
No | 104 (12.4) | Ref | |
Yes | 735 (87.6) | 2.13 (1.34, 3.38) | 0.001 |
Type 2 diabetes | | | |
No | 583 (69.5) | Ref | |
Yes | 256 (30.5) | 1.23 (0.91, 1.66) | 0.172 |
Current antilipidaemic medication | | | |
No | 750 (89.4) | Ref | |
Yes | 89 (10.6) | 1.49 (0.96, 2.32) | 0.075 |
High HCY | | | |
No | 708 (84.4) | Ref | |
Yes | 131 (15.6) | 2.40 (1.64, 3.51) | < 0.001 |
Continuous data are shown as the mean ± standard deviation or median (interquartile), and categorical data are shown as n (%). |
OR odds ratio, CI confidence interval, Ref reference |
Associations Of Non-hdlc/hdlc, Non-hdlc, And Hdlc With Carotid Plaques
Three logistic regression models were constructed to evaluate the independent effects of the non-HDLc/HDLc, non-HDLc, and HDLc on carotid plaques (Table 3). In the unadjusted model, the non-HDLc/HDLc, considered as a continuous variable (per unit increase), was significantly associated with the presence of carotid plaques (OR 1.23, 95%CI 1.07–1.40). In the minimally adjusted model, as the non-HDLc/HDLc increased by one unit, the chance of having carotid plaques increased by 32% (OR 1.32, 95%CI 1.13–1.53). In the fully adjusted model, for each additional unit of the non-HDLc/HDLc, the chance of having carotid plaques increased by 55% (OR 1.55, 95%CI 1.28–1.88). For the purpose of sensitivity analysis, the continuous non-HDLc/HDLc was converted into a categorical variable (tertiles), and the P for trend of the non-HDLc/HDLc with carotid plaques in the unadjusted or adjusted model was consistent with the results when the non-HDLc/HDLc served as a continuous variable. Similarly, continuous non-HDLc was significantly associated with carotid plaques (OR 1.73, 95%CI 1.42–2.11), which was also in agreement with the results after non-HDLc was converted into a categorical variable. However, HDLc treated either as a continuous or categorical variable was not significantly associated with carotid plaques in either the unadjusted or adjusted models. Additionally, the relationships between other crude blood lipid parameters and carotid plaques were also investigated. As shown in Table S1 (Additional file 2), in the fully adjusted model, continuous TC (OR 1.57, 95%CI 1.31–1.89) and LDLc (OR 1.71, 95%CI 1.37–2.13) were significantly associated with carotid plaques, whereas TG was not significantly associated with carotid plaques in either the unadjusted or adjusted models.
Table 3
Relationships between the non-HDLc/HDLc, non-HDLc, HDLc and carotid plaques
Variables | Unadjusted OR (95%CI, P) | Minimally adjusted OR (95%CI, P) | Fully adjusted OR (95%CI, P) |
non-HDLc/HDLc | 1.23 (1.07, 1.40) 0.003 | 1.32 (1.13, 1.53) < 0.001 | 1.55 (1.28, 1.88) < 0.001 |
non-HDLc/HDLc (tertile) | | | |
T1 | Ref | Ref | Ref |
T2 | 1.01 (0.72, 1.41) 0.974 | 1.12 (0.78, 1.62) 0.546 | 1.18 (0.81, 1.73) 0.393 |
T3 | 1.47 (1.05, 2.06) 0.026 | 1.65 (1.13, 2.41) 0.010 | 2.01 (1.29, 3.12) 0.002 |
P for trend | 0.027 | 0.010 | 0.002 |
non-HDLc (mmol/L) | 1.36 (1.16, 1.59) < 0.001 | 1.52 (1.27, 1.80) < 0.001 | 1.73 (1.42, 2.11) < 0.001 |
non-HDLc (tertile, mmol/L) | | | |
T1 | Ref | Ref | Ref |
T2 | 1.39 (0.99, 1.95) 0.059 | 1.63 (1.13, 2.37) 0010 | 1.78 (1.21, 2.63) 0.004 |
T3 | 1.86 (1.31, 2.62) < 0.001 | 2.26 (1.53, 3.31) < 0.001 | 2.61 (1.71, 3.98) < 0.001 |
P for trend | < 0.001 | < 0.001 | < 0.001 |
HDLc (mmol/L) | 0.93 (0.62, 1.40) 0.730 | 0.90 (0.57, 1.40) 0.634 | 0.90 (0.55, 1.47) 0.675 |
HDLc (tertile, mmol/L) | | | |
T1 | Ref | Ref | Ref |
T2 | 1.09 (0.77, 1.52) 0.632 | 1.20(0.83, 1.73) 0.334 | 1.20(0.81, 1.77) 0.372 |
T3 | 0.89 (0.64, 1.25) 0.515 | 0.89 (0.61, 1.30) 0.551 | 0.87(0.58, 1.32) 0.520 |
P for trend | 0.505 | 0.558 | 0.486 |
Minimally adjusted OR controlled for sex, age, region, education, employment status, BMI, exercise and smoking status, and family history of stroke |
Fully adjusted OR controlled for sex, age, region, education, employment status, BMI, SBP, DBP, FBG, TG, HCY, exercise and smoking status, family history of stroke, history of stroke and TIA, hypertension, type 2 diabetes, heart diseases and current antilipidaemic medication |
OR odds ratio, CI confidence interval, Ref reference |
Associations of the non-HDLc/HDLc with carotid plaques in prespecified and exploratory subgroups
Subgroup analyses explored possible associations of the non-HDLc/HDLc (treated as a continuous variable) with carotid plaques among different stratification variables (Table 4). The associations between the non-HDLc/HDLc and carotid plaques were similar among the following subgroups: age, region, overweight, smoking, family history of stroke, history of stroke, hypertension, type 2 diabetes, current antilipidaemic medication, and high HCY (all P interaction > 0.05). Noticeably, the non-HDLc/HDLc interacted significantly with three stratification variables, including sex (OR 1.31, 95%CI 1.02–1.68 for males versus OR 2.37, 95%CI 1.66–3.39 for females, P interaction = 0.016), exercise (OR 1.18, 95%CI 0.89–1.55 for subjects without lack of exercise versus OR 1.99, 95%CI 1.50–2.63 for subjects with lack of exercise, P interaction = 0.004) and heart diseases (OR 1.40, 95%CI 1.12–1.75 for subjects without heart diseases versus OR 3.12, 95%CI 1.88–5.20 for subjects with heart diseases, P interaction = 0.033).
Table 4
Associations of the non-HDLc /HDLc with carotid plaques in prespecified and exploratory subgroups
Stratification variable | N | Adjusted OR, 95%CI | P | P interaction |
Sex | | | | |
Male | 455 | 1.31 (1.02, 1.68) | 0.033 | 0.016 |
Female | 384 | 2.37 (1.66, 3.39) | < 0.001 | |
Age | | | | |
< 65 years | 451 | 1.57 (1.19, 2.07) | 0.002 | 0.717 |
≥65 years | 388 | 1.64 (1.24, 2.16) | 0.001 | |
Region | | | | |
Urban | 411 | 1.38 (1.07, 1.80) | 0.015 | 0.198 |
Rural | 428 | 1.78 (1.31, 2.42) | < 0.001 | |
Overweight | | | | |
No | 439 | 1.58 (1.20, 2.06) | 0.001 | 0.573 |
Yes | 400 | 1.48 (1.09, 1.99) | 0.011 | |
Lack of exercise | | | | |
No | 377 | 1.18 (0.89, 1.55) | 0.256 | 0.004 |
Yes | 462 | 1.99 (1.50, 2.63) | < 0.001 | |
Smoking | | | | |
No | 497 | 1.97 (1.46, 2.65) | < 0.001 | 0.129 |
Yes | 342 | 1.35 (1.01, 1.79) | 0.040 | |
Family history of stroke | | | | |
No | 663 | 1.59 (1.28, 1.98) | < 0.001 | 0753 |
Yes | 176 | 1.61 (0.98, 2.63) | 0.059 | |
History of stroke | | | | |
No | 663 | 1.51 (1.22, 1.87) | < 0.001 | 0.237 |
Yes | 176 | 2.34 (1.36, 4.02) | 0.002 | |
Heart diseases | | | | |
No | 635 | 1.40 (1.12, 1.75) | 0.003 | 0.033 |
Yes | 204 | 3.12 (1.88, 5.20) | < 0.001 | |
Hypertension | | | | |
No | 104 | 1.31 (0.57, 3.00) | 0.529 | 0834 |
Yes | 735 | 1.55 (1.26, 1.89) | < 0.001 | |
Type 2 diabetes | | | | |
No | 583 | 1.68 (1.31, 2.15) | < 0.001 | 0.144 |
Yes | 256 | 1.31 (0.95, 1.80) | 0.106 | |
Current antilipidaemic medication | | | | |
No | 750 | 1.58 (1.29, 1.94) | < 0.001 | 0.660 |
Yes | 89 | 1.27 (0.55, 2.95) | 0.579 | |
High HCY | | | | |
No | 708 | 1.63 (1.31, 2.04) | < 0.001 | |
Yes | 131 | 1.56 (0.95, 2.55) | 0.076 | 0.940 |
Note 1: Above model adjusted for sex, age, region, education, employment status, BMI, SBP, DBP, FBG, TG, HCY, exercise and smoking status, family history of stroke, history of stroke and TIA, hypertension, type 2 diabetes, heart diseases and current antilipidaemic medication |
Note 2: In each case, the model is not adjusted for the stratification variable |