Elsevier

Sleep Medicine

Volume 15, Issue 11, November 2014, Pages 1324-1331
Sleep Medicine

Original Article
Heart rate variability and cardiorespiratory coupling in obstructive sleep apnea: elderly compared with young

https://doi.org/10.1016/j.sleep.2014.05.028Get rights and content

Highlights

  • Young and elderly were evaluated by polysomnography.

  • Heart rate variability (HRV) and cardiorespiratory coupling (CRC) were analyzed during wakefulness and sleep.

  • Presence of obstructive sleep apnea (OSA) affected HRV in young subjects during wakefulness and sleep.

  • Age affected HRV during wakefulness and sleep in elderly subjects.

  • Young and elderly patients with OSA had significantly lower CRC during wakefulness.

Abstract

Introduction

Aging is known to be a major contributing factor to the increased risk of obstructive sleep apnea (OSA). With aging, breathing undergoes significant changes during sleep, increasing the prevalence of apnea events, which affects heart rate variability (HRV) and cardiorespiratory coupling (CRC).

Objectives

To compare HRV and CRC during wakefulness and sleep between young and elderly patients with and without OSA; and to determine whether the presence of OSA in young and elderly patients has a different impact on HRV and CRC during sleep.

Methods

One hundred subjects, 50 young (mean age, 27 ± 9; 20 normal and 30 OSA) and 50 elderly (mean age, 65 ± 7; 20 normal and 30 OSA), underwent polysomnography. Spectral, cross-spectrum, and HRV parameters were analyzed during wakefulness and sleep.

Results

The spectral analysis indicated that age affected HRV, with higher values of low frequency (P <0.05) in elderly subjects during wakefulness and an interaction between the presence of OSA and age. OSA influenced HRV during sleep with lower LF/HF ratios during stage 2 (S2) and rapid eye movement (REM) sleep (P <0.05), with an interaction between the presence of OSA and age in REM sleep. Elderly patients had significantly lower percent tachogram power coherent with respiration (%TPCR) during wakefulness (P <0.05), and OSA led to lower %TPCR during S2.

Conclusions

Age and OSA have an unfavorable impact on HRV, with reduced autonomic modulation during wakefulness, S2, and REM sleep. Age affects CRC during wakefulness and the presence of OSA affects CRC during sleep.

Introduction

Obstructive sleep apnea (OSA) is a respiratory disorder characterized by recurrent airflow obstruction caused by total or partial collapse of the upper airways [1], [2]. Aging is associated with increased apnea prevalence and is thus known to be a major factor contributing to the risk of OSA [3], [4]. Moreover, elderly adults with OSA are at greater risk for cardiovascular disease (i.e. coronary artery disease, congestive heart failure, ischemic disease, and stroke) [5], [6].

Cardiac autonomic function can be non-invasively assessed by analyzing the heart rate variability (HRV), which quantifies the changes in beat-to-beat intervals influenced by the combined effects of the sympathetic and parasympathetic nervous systems on the heart rate [7]. Clinical studies have consistently reported that decreased HRV is associated with sleep disorders [8], [9], [10]. During sleep, HRV is influenced by direct modulation of vagal efferent activity resulting from baroceptor responses to respiratory blood pressure fluctuations and from mechanical sinus node stretch determined by respiration-related changes in venous return [11].

Respiration undergoes important modifications during sleep and HRV is affected by sleep stage organization and by the presence of apnea events [12]. However, it is not known whether the effects of OSA on cardiac autonomic modulation in elderly subjects are different from those in young subjects, both during wakefulness and sleep. It is not known whether different effects are likely to be observed during specific sleep stages. Since OSA as it relates to the senescence process is considered a risk factor for cardiac autonomic impairment, we hypothesized that HRV and cardiorespiratory coupling (CRC) would be worse in elderly subjects with OSA.

Therefore, the aim of the study was to contrast HRV and CRC during wakefulness and sleep in young and elderly subjects with OSA. Further, we aimed to determine whether the presence of OSA in young and elderly subjects has a different impact on HRV and CRC during different stages of sleep.

Section snippets

Methods

This was a cross-sectional study, by analysis of medical records involving young and elderly patients referred to our sleep medicine clinic between January 2011 and December 2012 for evaluation of excessive daytime somnolence, snoring, and suspected OSA. The study protocol was approved by the Ethics Committee of Federal University of São Carlos (N.401/2010 opinion) and was registered as a clinical trial (RBR-3jbm6d). All participants signed informed consent prior to the polysomnography. The

Sample characteristics

One hundred examinations meeting the inclusion criteria for this study were selected: 50 young subjects (20 young and 30 OSA young) and 50 elderly subjects (20 elderly and 30 OSA elderly) (Table 1). Body mass index (BMI) was influenced by age and OSA, with an interaction between both. As expected, AHI was higher in OSA groups. Nadir saturation was lower in elderly + OSA subjects, and time spent with oxygen saturation <90% (T90) was influenced by both age and OSA (P <0.05). Likewise, the

Main results

The main results of our study may be summarized as follows: (i) the presence of OSA influenced HRV in young subjects to a greater degree, with a reduction in autonomic modulation during wakefulness and different sleep stages, whereas changes in HRV were only apparent during wakefulness in elderly subjects; (ii) age influenced HRV during wakefulness and sleep in elderly people; (iii) the presence of OSA influenced cardiorespiratory coupling only during wakefulness in both young and elderly

Conclusions

Our study reveals that the presence of OSA influenced HRV in young and elderly individuals, with reduced autonomic modulation during wakefulness and REM sleep. Age per se appeared to influence HRV during wakefulness and REM sleep in elderly subjects. Finally, the presence of OSA and age had an unfavorable impact on CRC during wakefulness and sleep. Thus, whereas OSA has negative effects on HRV and CRC across the lifespan, there seems to be an age-dependent influence with respect to how these

Funding sources

This study was supported by FAPESP 2009/01842-0 and CAPES 12883-12-3.

Conflict of interest

The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2014.05.028.

. ICMJE Form for Disclosure of Potential Conflicts of Interest form.

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