Effect of supervised integrated exercise on heart rate variability in type 2 diabetes mellitus

Background: Heart rate variability (HRV) reflects autonomic nervous system modulation of cardiac activity. There is a relationship between degrees of physical activity, HRV changes and the risk of cardiovascular disease. Aim: To study the effect of a supervised integrated exercise programme on HRV in type 2 diabetes mellitus (DM). Methods: The study group consisted of 48 patients (27 males, mean age 62±7 years) with type 2 diabetes, of whom 28 underwent a special exercise programme whereas the remaining 20 did not and served as the control group. The supervised integrated exercise programme was applied for a period of 9 months. Deep breathing time domain HRV (difference between the shortest and the longest R-R interval over one minute) was measured at baseline and after 3, 6 and 9 months. Results: A significant improvement in the HRV values was observed with increasing duration of exercise (13.03±1.08 beats/min at baseline versus 16.5±1.11 beats/min at 9 months, p <0.001) whereas HRV decreased in the control group (14.85±1.15 beats/min at baseline vs. 14.30±1.75 at 9 months, p <0.05). Favourable changes in HRV in the exercise group were gender-dependent and were significant in males (12.4±1.76 beats/min at baseline vs. 16.18±1.91 at 9 months, p <0.001) whereas in females only a trend towards HRV improvement was observed. The HRV changes were also age-dependent and were more pronounced in younger patients than in the elderly. The metabolic parameters of diabetes control (blood glucose and glycosylated haemoglobin levels) significantly improved in the exercise group and significantly worsened in the control group. Conclusions: Regular supervised integrated exercise significantly improves HRV in patients with type 2 DM, which may favourably influence their long-term prognosis.