Clinical characteristics of participants
The clinical characteristics of the participants stratified by glucose tolerance are summarized in Table 1. The study involved 3412 participants with NGR, 2475 with IGR and 1833 with type 2 diabetes. Among the participants with IGR, 773 (9.67 %) had isolated IFG, 1255 (15.7 %) had isolated IGT, and 717 (8.97 %) had combined IFG/IGT. The NGR and diabetes groups had, respectively, the most favorable and unfavorable metabolic profiles. Across different glucose tolerance, the subjects with higher blood glucose levels were more likely to be older, have higher waist to hip ratio, higher lipid profiles, and higher levels of blood pressure. Some liver and kidney function indicators (such as AST, ALT, GGT, SCr) between groups were different significantly. In addition, the levels of QTc interval were significantly increased in the subjects with isolated IFG, isolated IGT, combined IFG and IGT, and type 2 diabetes compared with the subjects with normal glucose regulation (416.63±24.79, 418.53±24.20,419.2±27.35, and 420.79±25.49, respectively, vs. 415.6±24.30, p < 0.05) (Fig. 1). QTc interval was positively associated with abnormal glucose metabolism.
Table 1
Clinical and laboratory characteristics according to different glucose tolerance.
Characteristics | DM | IFG+IGT | IGT | IFG | NGT | P value |
N | 1833 | 717 | 1255 | 773 | 3412 | |
Age (yr) | 58.21±7.20 | 56.86±7.46 | 55.22±7.60 | 55.56±7.60 | 53.47±7.79 | <0.001 |
Gender (M/F) | 747/1086 | 253/464 | 307/948 | 316/457 | 866/2546 | <0.001 |
QTc | 420.79±25.49 | 419.20±27.35 | 418.53±24.20 | 416.63±24.79 | 415.60±24.30 | <0.001 |
BMI (kg/m2) | 25.18±3.38 | 25.06±3.53 | 24.91±10.43 | 24.38±3.35 | 23.74±3.25 | <0.001 |
WHR | 0.90±0.07 | 0.89±0.09 | 0.88±0.10 | 0.88±0.08 | 0.86±0.08 | <0.001 |
SBP (mm Hg) | 136.51±19.00 | 133.38±17.22 | 127.74±17.37 | 130.81±18.01 | 123.80±18.42 | <0.001 |
DBP (mm Hg) | 81.78±10.37 | 82.10±9.51 | 79.97±9.89 | 80.87±9.66 | 77.79±10.52 | <0.001 |
FBG (mmol/l) | 8.05±2.59 | 6.38±0.24 | 5.57±0.34 | 6.34±0.22 | 5.41±0.37 | <0.001 |
PBS (mmol/l) | 13.41±4.83 | 9.09±0.89 | 8.92±0.84 | 6.28±1.02 | 6.08±1.05 | <0.001 |
HbA1C (%) | 6.91±1.61 | 5.83±0.41 | 5.74±0.39 | 5.71±0.41 | 5.60±0.40 | <0.001 |
Insulin(pmol/l) | 8.92±3.24 | 8.10±3.89 | 7.27±3.66 | 7.26±3.35 | 6.27±3.07 | <0.001 |
HOMA-IR | 3.23±0.94 | 2.36±0.92 | 1.85±0.93 | 2.11±0.97 | 1.56±0.78 | <0.001 |
HDL (mmol/L) | 1.22±0.32 | 1.23±0.33 | 1.22±0.28 | 1.28±0.33 | 1.25±0.32 | <0.001 |
LDL (mmol/L) | 2.70±0.79 | 2.71±0.73 | 2.60±0.73 | 2.72±0.76 | 2.51±0.74 | <0.001 |
CHO (mmol/L) | 4.86±1.08 | 4.85±0.99 | 4.61±0.99 | 4.84±1.02 | 4.45±0.98 | <0.001 |
TG (mmol/L) | 2.08±1.71 | 2.02±1.11 | 1.73±0.89 | 1.70±0.91 | 1.38±0.71 | <0.001 |
ALT (U/L) | 20.86±10.07 | 19.04±10.31 | 16.99±8.80 | 17.28±8.04 | 13.97±7.55 | <0.001 |
AST (U/L) | 22.80±10.95 | 21.88±10.16 | 20.57±9.22 | 21.36±8.76 | 18.89±9.03 | <0.001 |
GGT (U/L) | 38.96±14.55 | 33.49±32.77 | 28.55±36.90 | 31.04±14.14 | 22.05±11.11 | <0.001 |
Scr (umol/L) | 68.71±17.48 | 68.07±19.95 | 64.03±12.94 | 67.91±14.05 | 63.34±12.06 | <0.001 |
Smoking (n/total) | 492/3412 | 161/773 | 156/1255 | 115/717 | 359/1833 | <0.001 |
Drinking (n/total) | 705/3412 | 222/773 | 227/1255 | 179/717 | 449/1833 | <0.001 |
Values are mean ± SD or median (interquartile range) or number (proportion) |
p values were for the ANOVA or χ2 analyses across the five groups |
Association between QTc interval and clinical characteristics
Table 2 presents the results of correlation analyses of QTc interval with metabolic related parameters. QTc levels correlated positively with age, gender, WHR, SBP, DBP, PBS, FBS, HBA1c, insulin, HOMA-IR, LDL, CHO, TG, smoking, drinking. After adjusting for age and gender, WHR, SBP, DBP, PBS, FBS, HA1c, insulin, HOMA-IR, CHO, TG was still positively associated with QTc interval.
Table 2
Crude and partial correlation between QTc and clinical parameters in the studied subjects
Variable | Crude r | Partial r† |
Age (year) | 0.139** | - |
Gender | 0.148** | - |
BMI (kg/m2) | 0.01 | 0.006 |
WHR | 0.031* | 0.039* |
SBP (mmHg) | 0.094** | 0.085** |
DBP (mmHg) | 0.054** | 0.081** |
PBS (mmol/L) | 0.091** | 0.075** |
FBS (mmol/L) | 0.084** | 0.083** |
HbA1c (%) | 0.074** | 0.053** |
Insulin (pmol/L) | 0.061** | 0.045** |
HOMA_IR | 0.068** | 0.054** |
HDL (mmol/L) | 0.014 | 0.004 |
LDL (mmol/L) | 0.046** | 0.021 |
CHO (mmol/L) | 0.068** | 0.041** |
TG (mmol/L) | 0.062** | 0.071** |
Smoking | -0.106** | -0.002 |
Drinking | -0.083** | -0.007 |
*p < 0.01, **p < 0.001, †adjusted for age, gender |
Determinants of QTc levels
Table3 demonstrated variables independently associated with QTc interval. Age, gender, SBP, DBP, PBS, FBS, HBA1c, TG were independent determinants for QTc interval.
Table 3
Multiple stepwise regression analysis showing variables independently associated with QTc.
Independent variables | Standardized β | t | P value |
Age | 0.125 | 10.615 | <0.001 |
Sex | 0.192 | 17.004 | <0.001 |
FBS | 0.065 | 5.706 | <0.001 |
PBS | 0.052 | 4.557 | <0.001 |
HbA1c | 0.043 | 3.819 | <0.001 |
SBP | 0.044 | 3.007 | 0.003 |
DBP | 0.036 | 2.498 | 0.012 |
TG | 0.049 | 4.358 | <0.001 |
The analysis also included CHO, WHR, Insulin, BMI, smoking, and drinking which were all excluded from the model. |
Associations between different glucose tolerance and QTc interval
To further explore the relationship between different glucose tolerance and QTc interval, multiple regression analyses were performed. The analyses revealed that solated IGT, combined IFG/IGT and type 2 diabetes are significantly associated with QTc interval after adjusting for all potentially confounders (age, sex, insulin, SBP, DBP, CHOL, TG, smoking, and drinking) (Table4).
Table 4
Adjusted associations with QTc according to different glucose tolerance.
| Glucose tolerance category | Standardized β | t | P value |
Model 1 | NGT IFG IGT IFG+IGT DM | reference 0.012 0.043 0.041 0.087 | 1.042 3.561 3.522 7.196 | 0.298 <0.001 <0.001 <0.001 |
Model 2 | NGT IFG IGT IFG+IGT DM | reference 0.027 0.044 0.032 0.076 | 1.938 3.043 2.279 5.049 | 0.053 0.002 0.023 <0.001 |
Model 1 not adjusted. |
Model 2 adjusted for age, sex, insulin, SBP, DBP, CHOL, TG, smoking, and drinking. |
Associations between different glucose tolerance and QTc prolongation
In the present study, we consider QTc༞440 ms as abnormally prolonged. Taken NGR as reference, isolated IGT, combined IFG and IGT, and type 2 diabetes were all risk factors for prolonged QTc. OR of IGT for QTc prolongation was 1.131 (95% CI 1.059–1.356), OR of IFG+IGT for QTc prolongation was 1.396 (95% CI 1.126–1.73), and OR of T2DM for QTc prolongation was 1.34 (95% CI 1.142–1.577), respectively (P for trend < 0.001) after adjusting for age, sex, insulin, SBP, DBP, CHOL, TG, smoking, and drinking (Table5).
Table 5
Adjusted ORs and 95% CIs for prolonged QTc according to different glucose tolerance.
Glucose tolerance categary | n/total | Crude OR (95%CI) | Adjusted OR (95%CI) |
NGT | 483/3412 | 1 | 1 |
IFG | 121/773 | 1.129 (0.910-1.402) | 1.110 (0.888-1.387) |
IGT | 216/1255 | 1.264* (1.061-1.506) | 1.131* (1.059-1.356) |
IFG+IGT | 144/717 | 1.538** (1.251-1.890) | 1.396** (1.126-1.730) |
DM | 361/1833 | 1.486** (1.279-1.727) | 1.342** (1.142-1.577) |
Adjusted OR: Adjusted for age, sex, lipid profiles, BMI, SBP, and DBP, smoking, and drinking. |
*p < 0.01, **p < 0.001 |