Abstract
Baroreflex function measured as baroreflex sensitivity (BRS) mirrors an integrated capacity of the autonomic nervous system. We aimed to assess the relationship between measures of BRS and age and relevant clinical characteristics. 80 subjects participating in the Copenhagen City Heart study (43 women) with a mean age of 59 ± 11 years (range 41-79 years) were included. Baroreceptor activity was quantified through the Valsalva manoeuvre (VM) and as a spontaneous function. BRS was tested against age, gender, smoking status, body size and predicted risk of coronary heart disease based on the Framingham score. BRS was found to decline with age, but this change disappeared when correcting for the age related increase in systolic blood pressure. We found that the VM-derived indices of sympathetic vascular control declined with age as did the vagally controlled heart rate changes in response to deep breathing and VM. We could not demonstrate any correlation between BRS, smoking status, and body size when adjusting for age and gender, whereas spontaneous BRS was reduced with increasing Framingham risk score. Principal component analysis revealed three component explaining 69% of the total variance in our population comprising one component reflecting the sympathetic activity, the parasympathetic system, and the integrated spontaneous BRS, respectively. The parasympathetic component was the only one correlating with clinical characteristics of declining age, smoking habits, systolic blood pressure and Framingham score. It is concluded that the parasympathetic and sympathetic parts of the baroreflex arch behave differently with respect to aging and cardiovascular risk factors. The most prominent changes are seen in cardiovagal control whereas the effects of age related changes in sympathetic vascular control are less noticeable. Our study supports the use of the cardiovagal part of the baroreflex arch as an indicator of cardiovascular risk.
Highlights
Baroreflex function measured as baroreflex sensitivity (BRS) mirrors an integrated capacity of the autonomic nervous system and is an established tool for the assessment of autonomic control of the cardiovascular system
This distinction between the effect on heart rate and the vascular system is reflected in the division of baroreflex sensitivity in a part that causes a change in the interbeat interval and a part that changes sympathetic nerve activity or vascular tone
Adrenergic indices (PRT, BRSa and BRSa1) could not be calculated in 12 patients as the systolic blood pressure (SBP) in Phase III did not decrease below baseline values
Summary
Baroreflex function measured as baroreflex sensitivity (BRS) mirrors an integrated capacity of the autonomic nervous system and is an established tool for the assessment of autonomic control of the cardiovascular system. In the original study by Hering [1], it was demonstrated that stimulation of the nerves from the carotid sinus induced cardiac slowing and vasodilatation with the latter being independent on the bradycardia This distinction between the effect on heart rate and the vascular system is reflected in the division of baroreflex sensitivity in a part that causes a change in the interbeat interval (cardiovagal BRS) and a part that changes sympathetic nerve activity or vascular tone (adrenergic BRS). Both cardiovagal and adrenergic BRS has been shown to be blunted with increasing age in a mutual independent manner [2]. Smoking increases sympathetic activity [9] and a number of studies have demonstrated that - compared to non-smokers - smokers have higher heart rates, diminished heart rate variability,
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