Sex difference in the relationship between insulin resistance and corrected QT interval in non-diabetic subjects

Background: Men with a prolonged corrected QT (QTc) interval have an increased risk of cardiovascular mortality and sudden death, even in healthy individuals. In addition, prolonged QTc is a predictor of mortality in diabetics. However, the relationship between insulin resistance and QTc is not clarified in non-diabetic healthy people. The present study was performed to observe the association between QTc and insulin resistance in Korean non-diabetic subjects. Methods and Results: In the current study there was a total of 874 subjects (520 men, 354 women, mean age: 45.9±11.0 years) who underwent a medical check-up at the health promotion center at Kangbuk Samsung Hospital from January 2002 to May 2002. Age, sex, height, body weight, blood pressure, blood cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), fasting insulin, and fasting glucose levels were measured. The QT intervals were corrected using Bazett's formula (QTc=QT/√RR). Homeostasis model assessments (HOMA) were performed to assess the correlation between insulin resistance indices and the QTc interval. The mean QTc interval was significantly longer in females (417±24ms) than in males (402±23ms) (p<0.001). After adjusting the variables related to the QTc interval, the differences in QTc between men and women were statistically significant (p<0.001). A significant positive correlation was found between QTc and age, glucose, and blood pressure in male subjects. Female subjects showed positive correlation between QTc and age, glucose, blood pressure, total cholesterol, low-density lipoprotein cholesterol, triglyceride, fasting insulin, and the HOMA index, and a negative correlation between QTc and HDL-C. Multiple regression analysis showed that in men, age (β=0.480, p<0.001) and diastolic blood pressure (β=0.280, p<0.001) were predictors of QTc. In women, age (β=0.321, p=0.008), diastolic blood pressure (β=0.324, p=0.006) and HOMA index (β=3.508, p=0.033) were predictors of QTc. Conclusions: The present study of Korean healthy subjects shows that QTc was more prolonged in females than in males. In normoglycemic female subjects, insulin resistance was an independent determinant of the prolongation of QTc.