Abstract:
Cardiovascular disease is a major public health concern and it can be modified by diet, exercise and health awareness. However the impact of these interventions on the autonomic control of heart rate as measured by heart rate variability (HRV) is controversial. The aim of this study was to determine if indicators of HRV can be used to identify moderate risk of cardiovascular disease and to compare the influence of different lifestyle interventions in a student population. This was a double blind, randomised, prospective, pre-test, post-test group comparison. Thirty-seven university students at moderate risk of cardiovascular disease and 37 age matched controls, participated. HRV indicators as determined by time and frequency domain analysis were measured before and after interventions of exercise, diet, health awareness and a combination intervention. There were no significant pre-intervention differences between the healthy and test groups. Supine HRV parameters changed minimally in the health awareness and dietary groups during post testing. In the combined group, supine parameters were unchanged, however the standing parameters: standard deviation, root mean square successive difference and normalized high frequency decreased and normalized low frequency increased (p<0.05). HRV indicators of the other groups were unchanged. Analysis of HRV is insensitive to distinguish between healthy students and those at moderate risk of cardiovascular disease. However, HRV measured during an orthostatic stressor, was able to measure a significant parasympathetic withdrawal upon standing in the combined group indicating improved autonomic response to postural change in the combined intervention of health awareness, dietary adaptation and exercise.
