Accurate assessment of nocturnal blood pressure fall in patients with type 2 diabetes mellitus and resistant hypertension

Aim. To study the relationship between nocturnal blood pressure (BP) fall and kidney damage, the severity of obesity and markers of sympathetic activity in patients with type 2 diabetes mellitus (DM2) combined with resistant hypertension (HTN) depending on the accuracy of its assessment. Material and methods. The cross-sectional study included 64 patients with DM2 and resistant HTN, mean age 60.5±7.7 years (38 women), 24-hour BP (systolic/diastolic) (SBP/DBP) 155.9±16.7/81.4±12.7 mm Hg, HbA1c 7.3±1.5%. Patients underwent evaluation of free metanephrine, normetanephrine and lipocalin-2 levels in the blood, 24h urinary albumin excretion (UAE), 24h blood pressure monitoring and electrocardiography with assessment of heart rate variability (HRV) (low-frequency (LF) and high-frequency (HF) components). Nocturnal BP fall was determined using the standard (with a fixed sleep time interval of 23-7 h) and optimized methods (using a mathematical algorithm for detecting the nocturnal sleep period). Results. Significant correlations were found between the degree of nighttime decrease in SBP, calculated by the optimized method, but not by standard method, and HRV indices (r= -0.64, p<0.001 for LF; r=0.55 p=0.004 for HF; r= -0.65 p<0.001 for the LF/HF ratio), with the level of normetanephrines (r= -0.47, p=0.025), UAE (r= -0.47, p=0.008) and lipocalin-2 (r= -0.52, p=0.012). In patients with a body mass index (BMI)≥35 kg/m2, degree of nighttime decrease in SBP according to the optimized method was 2.5 times lower than in individuals with a BMI<35 kg/m2 (3.5±5.5 and 8.7±6.6%, respectively, p=0.003). Conclusion. In type 2 diabetic patients with resistant hypertension, the degree of nocturnal blood pressure fall calculated on the basis of objective determination of the time of night rest, in contrast to the standard method, is closely associated with markers of kidney damage, the severity of obesity, clinical and laboratory signs of sympathetic activity.