The study included a group of 46 adolescents with type 1 diabetes mellitus (DM1) and an average diabetes duration of 7.38 ± 3.48 years. These patients were admitted to the Department of Pediatric Diabetology, Auxology, and Obesity at Poznan University of Medical Sciences, Poland, for diabetes assessment, including hypertension evaluation.
Ambulatory blood pressure monitoring (ABPM) using the Mobil-O-Graph device – the Pulse Wave Analysis Monitor (Mobil-O-Graph; IEM, Stolberg, Germany) – was initiated upon discharge from the hospital. The Mobil-O-Graph device incorporates the ARCSolver method (Austrian Institute of Technology, Vienna, Austria), which utilizes a transfer function to reconstruct the central or aortic pulse wave from brachial oscillometric pressure. Central data were recorded for approximately 10 seconds at the diastolic blood pressure level (+- 5 mmHg) using a high-fidelity pressure sensor (MPX5050; Freescale, Tempe, Arizona) [12, 13].
Initially, the brachial circumference was measured to determine the appropriate cuff size for each participant. ABPM measurements were programmed to occur every 20 minutes during the day (7 am–11 pm) and every 30 minutes during the night (11 pm–7 am). Parents and children were instructed to maintain a diary of daily activities during the ABPM measurement period. The cuff was placed on the non-dominant arm, and participants were advised to avoid vigorous physical exercise while wearing the ABPM device, but to carry out their usual daily activities. A minimum of 40 valid recordings was required for ABPM analysis.
Ambulatory blood pressure normal values for children, as defined by Wuhl et al., were used in this study [14]. The study group was divided into three subgroups based on blood pressure results. Patients were classified as hypertensive (HA) if their systolic or diastolic blood pressure was equal to or above the 95th percentile, or if blood pressure load exceeded 50% during the 24-hour period, daytime, or nighttime. Prehypertensive children (preHA) exhibited blood pressure below the 95th percentile but equal to or above the 90th percentile, or blood pressure load between 25% and 50% during the 24-hour period, daytime, or nighttime. Normal blood pressure was defined as below the 90th percentile and blood pressure load below 25% during the 24-hour period, both daytime and nighttime.
Table 1 presents the ABPM parameters analyzed in this study, including peripheral and central blood pressure, as well as mean arterial pressure (MAP). Arterial stiffness indexes, such as pulse wave velocity (PWV), augmentation index (Alx@75), coefficient of reflection (CR), peripheral pulse pressure (pPP), central pulse pressure (cPP), and pulse pressure amplification (PPA), were also evaluated. PWV was determined using a mathematical model that considered various parameters in pulse wave and wave separation analysis. Alx@75 was calculated by determining the pressure difference between the reflection wave peak (P2) and the incident wave peak (P1), expressed as a percentage of pulse pressure [Alx@75=(P2-P1)/PPc x 100] [15].
Hemodynamic parameters, including total vascular resistance (TVR), heart rate (HR), cardiac output (CO), and cardiac index (CI), were also studied. The load of systolic and diastolic blood pressure, as well as the diurnal blood pressure rhythmicity over 24 hours, were assessed. Non-dippers were identified as individuals with a reduction in blood pressure of less than 10% from day to night in either systolic or diastolic blood pressure. Diurnal blood pressure rhythmicity analysis was performed separately for systolic and diastolic blood pressure.
All study subjects underwent blood and urine tests. Urinary albumin excretion (UAE) was assessed through 24-hour urine collection. Kidney function was estimated using glomerular filtration rate (eGFR) based on the Filler formula, which incorporates cystatin C [16, 17]. Moderate albuminuria (between 30 and 300 mg/24 hours) was observed in six patients.
Long-term glycemic control was evaluated using hemoglobin A1c (HbA1c) levels [18]. Urinary sodium excretion (uNa), fractional sodium excretion (FNa), serum uric acid (UA), and neutrophil-lymphocyte ratio (NLR) were also analyzed.
None of the patients were receiving antihypertensive therapy at the time of the investigation. Patients with a history of conditions affecting blood pressure, particularly heart and kidney diseases, as well as those with other serious diseases or factors influencing blood pressure, such as drug abuse or smoking, were excluded. All subjects were instructed to continue their normal sodium intake, and no medication other than insulin was allowed. Due to retrospective analysis the ethics review board approval was not required for the study.
The control group consisted of 15 healthy children (number of males and females) recruited from adolescents hospitalized in the Department of Pediatric Nephrology and Hypertension, where hypertension was excluded based on ABPM.
Statistical analysis
Statistical analysis was performed using Statistica ver. 8 (StatSoft, Tulsa, OK). The data are reported as the mean±standard deviation. Normally distributed continuous variables were tested using the analysis of variance with Scheffe post-hoc test. In all other cases, non-parametric tests were applied using the Mann–Whitney test. The relationship between two variables was assessed by Spearman’s rank correlation coefficient. The level of significance was set at p <0.05.