We measured baPWV with a noninvasive pulse wave analyzer (form PWV/ABI, Colin Co., Komaki, Japan) in 2,728 consecutive type 2 diabetic patients in Department of Endocrinology and Metabolism, Pusan National University Hospital, between January 2008 to January 2011. Among these, we retrospectively included patients aged between 30 and 39 yr (n = 145). Those who had hypertension, current antihypertensive medication, atherosclerotic vascular disease, chronic kidney disease (eGFR < 60 mL/min/1.73 m²), moderate to severe heart disease (previous coronary artery disease and heart failure with NYHA class II-IV) and low ankle brachial index (< 0.9) were excluded. Presence of hypertension was defined when the subject was taking anti-hypertensive medication or measured systolic or diastolic blood pressures were same or above 130/80 mmHg. A total of 103 patients with type 2 DM were finally included in this study.

Blood pressures (BP) were taken with a standardized sphygmomanometer after at least 5 min of rest. The height and weight of the subjects were measured just before examining baPWV. The body mass index (BMI) was expressed as the weight in kilograms divided by squared height in meters (kg/m²). The waist circumference was measured in the standing position, at the level of umbilicus by a single examiner. Blood samples were collected after at least 8 hr of fasting. Plasma glucose, serum insulin, C-peptide, lipid profile, high sensitive-C-reactive protein (hs-CRP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transpeptidase (γ-GTP) were checked concurrently in study day. HbA1c was measured by high performance liquid chromatography using the Variant TM II Turbo (Bio-Rad Laboratories, Hercules, CA, USA). Also, we investigated history of smoking, alcohol intake and medication by questionnaire.

After the subject had rested in a supine position for more than 5 min, the measurement of baPWV was conducted using a waveform analyzer (VP-2000; Colin Co Ltd, Komaki, Japan). Electrocardiographic electrodes were placed on both wrists, a microphone was placed on the left edge of the sternum to detect heart sounds, and pneumatic cuffs were placed on both arms and ankles. The cuffs were connected to a sensor that determined volume pulse form and an oscillometric pressure sensor that measured blood pressure. The characteristic points of waveforms were determined automatically according to the pulse velocity theory. The components over 5 Hz were stored using a pass filter and the wave front was determined. The time interval between the wave front of brachial waveform and that of ankle waveform was defined as the time interval between brachium and ankle (ΔTba). The distance between sampling points of baPWV was calculated automatically according to the subject's height. The path length from the heart to the brachium (Lb) was measured externally and was expressed using the following equation: Lb = 0.2195 × height of the patient (cm) - 2.0734. The path length from the heart to the ankle (La) was expressed using the following equation: La = 0.8129 × height of the patient (cm) + 12.328. Finally, baPWV was calculated from the following equation: baPWV = (La-Lb)/ΔTba (18).

The statistical analysis was performed using the SPSS (SPSS ver 17.0 for Windows, Chicago, IL, USA) software package. All data were expressed by mean ± S.D. for normally distributed values and median (interquartile range) for nonparametric values. Pearson chi-square test was used to assess differences in categorical data between male and female. And Student t-test and Mann Whitney U test were used to assess numerical data as appropriate. Bivariate correlation (Pearson's correlation coefficient) analyses were performed to analyze the relationships between maximal baPWV and other numerical data. To approximate normal distribution, natural log transformed value for Urine Albumin/Creatinine ratio (microalbuminuria) was used in this analysis. Linear regression analysis was performed to evaluate the association between maximal baPWV and other clinical data. And step-wise multiple regression analysis was performed to determine the correlation and independent variables for maximal baPWV. A value of P < 0.05 was considered to be statistically significant.

The study was approved by the institutional review board of the Pusan National University Hospital, Busan, Korea (No. 2009041). According to this, we obtained all patients' informed consent.

Table 1 shows the general characteristics of the study population. Pulse, fasting glucose, γ-GTP, hs-CRP, serum creatinine, smoking, alcohol intake and statin treatment were different significantly between male and female.

Table 2 shows correlations between baPWV and clinical parameters in total patients.

Maximal baPWV was positively correlated with mean blood pressure (r = 0.404, P < 0.001), heart rate (r = 0.285, P = 0.004), AST (r = 0.409, P < 0.001), ALT (r = 0.329, P = 0.001), γ-GTP (r = 0.273, P = 0.006), urine albumin/creatinine ratio (r = 0.321, P = 0.003). We compared baPWV according to smoking, anti-platelet treatment, alcohol intake, and statin treatment. Smoking and statin therapy showed significant positive correlation (P = 0.033, P = 0.020).

Table 3 shows correlations between baPWV and clinical variables in male and female patients respectively. Mean blood pressure, AST, ALT, γ-GTP, and triglyceride were positively correlated with maximal PWV in both groups. Heart rate and urine albumin/creatinine ratio were positively correlated with maximal baPWV only in male group (P = 0.001, P = 0.001). The c-peptide was positively correlated with maximal baPWV only in female group (P = 0.012).

Including these significant variables and well-known baPWV-related variables, we performed multivariate linear regression analyses for the association between several variables and maximal baPWV (Table 4). These analyses were performed in male, female and total group, respectively. Mean blood pressure and heart rate were significantly associated with maximal baPWV in male and total group. And in female group, mean blood pressure was the only variable associated with maximal baPWV.