Brazil: A recent study published in the journal Frontiers in Endocrinology showed that high fasting blood sugar level in patients with type 2 diabetes (T2D) is associated with cardiac autonomic dysfunction. According to the study, patients with T2D showed lower parasympathetic modulation at rest and slowed heart rate recovery (HRR) in response to physical exercise implying glycemic profile to be an important predictor of impaired cardiac autonomic modulation.
Type 2 diabetes is a chronic disease characterized by a metabolic disorder that increases blood glucose concentration. Chronic hyperglycemia is known to be associated with several complications in such patients. Cardiac autonomic dysfunction is one such complication that can be assessed from heart rate variability (HRV) and heart rate recovery (HRR) response -- both associated with many aspects of fitness and health, including severe cardiovascular outcomes.
Against the above background Lucas Raphael Bento Silva, Department of Physical Education, Araguaia University Center, Goiânia, Brazil, and colleagues aimed to evaluate the effects of T2D on cardiac autonomic modulation by means of HRV and HRR measurements.
The study is an observational study with the characteristic of case control. It involved ninety-three middle-aged adults stratified into two groups (control group - CG, n = 34; diabetes group - DG, n = 59). Following their consent through a free and informed consent form, the patients were submitted to the evaluation protocols, performed biochemical tests to confirm the diagnosis of T2D, collection of R-R intervals for HRV analysis, and cardiopulmonary effort test to quantify HRR.
The study found the following:
At rest, the DG showed a reduction in global HRV (SDNN= 19.31 ± 11.72 vs CG 43.09 ± 12.74), lower parasympathetic modulation (RMSSD= 20.49 ± 14.68 vs 52.41 ± 19.50, PNN50 = 4.76 ± 10.53 vs 31.24 ± 19.24, 2VD%= 19.97 ± 10.30 vs 28.81 ± 9.77) and higher HRrest when compared to CG.
After interruption of physical exercise, a slowed heart rate response was observed in the DG when compared to the CG.
A simple linear regression showed that fasting glycemia was able to predict cardiac autonomic involvement in volunteers with T2D.
"T2D patients presented impairment in cardiac autonomic modulation with greater sympathetic modulation and lower vagal modulation versus healthy people at rest and in response to physical exercise," wrote the authors. "Fasting glycemia was associated with cardiac autonomic dysfunction.*"
Reference:
Silva LRB, Gentil P, Seguro CS, de Oliveira GT, Silva MS, Zamunér AR, Beltrame T and Rebelo ACS (2021) High Fasting Glycemia Predicts Impairment of Cardiac Autonomic Control in Adults With Type 2 Diabetes: A Case-Control Study. Front. Endocrinol. 12:760292. doi: 10.3389/fendo.2021.760292