Influence of smoking and other cardiovascular risk factors on heart rate circadian rhythm in normotensive and hypertensive subjects.

Agostino Accardo,Lorenzo Pascazio,Milos Ajčević,Giulia Silveri,Aleksandar Miladinović

doi:10.1371/journal.pone.0257660

Abstract

Circadian heart rate (HR) is influenced by hypertension and other cardiovascular risk factors particularly smoking, obesity and dyslipidemia. Until now, to evaluate the HR changes due to presence of these risk factors, a single HR office measure or a mean evaluated on day time or night time or 24h was used. However, since HR shows a circadian behavior, a single value represents only a rough approximation of this behavior. In this study, we analyzed the influence of smoking, obesity and dyslipidemia on the circadian rhythm in normotensive and hypertensive subject groups presenting only one of these risk factors. The 24h HR recordings of 170 normotensive (83 without risk factors, 20 smokers, 44 with dyslipidemia, 23 obese) and 353 hypertensive (169 without risk factors, 32 smokers, 99 with dyslipidemia, 53 obese) subjects were acquired using a Holter Blood Pressure Monitor. Results highlighted a specific circadian behavior with three characteristic periods presenting different HR means and rates of HR change in the eight subject groups. The slopes could be used both to estimate the morning HR surge associated with acute cardiovascular effects in the awakening and to evaluate the decline during the night. Moreover, we suggest to use three HR mean values (one for each identified period of the day) rather than two HR values to better describe the circadian HR behavior. Furthermore, smoking increased and dyslipidemia decreased mean HR values from 10:00 to 04:00, both in normotensive and hypertensive subjects in comparison with subjects without risk factors. In this time interval, hypertensive obese subjects showed higher values while normotensive ones presented quite similar values than subjects without risk factors. During the awakening (05:00–10:00) the slopes were similar among all groups with no significant difference among the mean HR values.

Highlights

Heart rate (HR) is a clinical parameter that reflects the autonomic system activity and reflects the balance of sympathetic and parasympathetic nerves
In order to separately evaluate the influence of specific risk factors on the HR circadian rhythm, in this study we carefully examined how the rhythm during 24h changes in normotensive and hypertensive subjects presenting only one risk factor at a time
Comparing hypertensive and normotensive subjects considering the same risk factor, our results showed no significant differences between N and H in the three periods, confirming the findings of [15] obtained during day time and night time and 24h, suggesting a primary role of central nervous mechanisms in both subject groups and highlighting that the marked impairment of the arterial baroreceptor did not modify HR variabilities

Summary

Introduction

Heart rate (HR) is a clinical parameter that reflects the autonomic system activity and reflects the balance of sympathetic and parasympathetic nerves. The heart rate measured in office condition is both a potential clinical parameter and a prognostic marker of cardiovascular system due to its association with a wide range of chronic diseases, cardiovascular incidents and all cause of mortality [1,2]. The Fraingham study [3] identified heart rate as a powerful independent risk factor for cardiovascular morbidity and mortality linking heart rate to myocardial infarction, stroke and death in healthy people [1] as well as in patients with hypertension [4]. Conventional office HR measurement has long been used to evaluate physiological states [3] they do not provide additional prognostic information about short and long term fluctuations during the day [6] as estimated by using the 24h

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