Chest
Volume 142, Issue 5, November 2012, Pages 1222-1228
Journal home page for Chest

Original Research
Sleep Disorders
Inverse Relationship of Subjective Daytime Sleepiness to Sympathetic Activity in Patients With Heart Failure and Obstructive Sleep Apnea

https://doi.org/10.1378/chest.11-2963Get rights and content

Background

Patients with heart failure (HF) and obstructive sleep apnea (OSA) are less sleepy than patients with OSA but without HF. Furthermore, unlike the non-HF population, in the HF population, the degree of daytime sleepiness is not related to the apnea-hypopnea index (AHI). The sympathetic nervous system plays a critical role in alertness. HF and OSA both increase sympathetic nervous system activity (SNA) during wakefulness. We hypothesized that in patients with HF and OSA, the degree of subjective daytime sleepiness would be inversely related to SNA.

Methods

Daytime muscle SNA (MSNA) was recorded in patients with HF and OSA. Subjective daytime sleepiness was assessed by the Epworth Sleepiness Scale (ESS).

Results

We studied 27 patients with HF and OSA and divided them into two groups based on the median ESS score: a less sleepy group, with an ESS score < 6 (n = 13), and a sleepier group, with an ESS score ≥ 6 (n = 14). The less sleepy group had higher MSNA than did the sleepier group (82.5 ± 9.9 bursts/100 cardiac cycles vs 69.3 ± 18.6 bursts/100 cardiac cycles; P = .037) and a longer sleep-onset latency (33 ± 29 min vs 14 ± 13 min; P = .039). The ESS score was inversely related to MSNA (r = −0.63; P < .001) but not to the AHI, arousal index, or indices of oxygen desaturation.

Conclusions

In patients with HF and OSA, the degree of subjective daytime sleepiness is inversely related to MSNA. This relationship is likely mediated via central adrenergic alerting mechanisms. These findings help to explain the previously reported lack of daytime hypersomnolence in patients with HF and OSA.

Section snippets

Subjects

Subjects were recruited from the HF clinics of the Mount Sinai Hospital and University Health Network/Toronto General Hospital without regard to whether they had any complaints of EDS or other symptoms of sleep apnea. Inclusion criteria were (1) HF with systolic dysfunction (left ventricle ejection fraction [LVEF] < 45% by two-dimensional echocardiography or radionuclide angiography); (2) stable condition and without medication adjustment for at least 1 month prior to participation; and (3) OSA

Results

Twenty-seven patients met the inclusion criteria. Their mean age was 50 ± 13 years; BMI, 31.7 ± 6.1 kg/m2; LVEF, 25.9% ± 7.9%; AHI, 39 ± 18 events/h of sleep; arousal index, 35 ± 18 events/h of sleep; mean Sao2, 94.2% ± 2.5%; minimal Sao2, 79% ± 10%; mean ESS score, 6.4 ± 3.3; and mean MSNA, 75 ± 17 bursts/100 cardiac cycles or 56 ± 11 bursts/min. Characteristics of the 13 less sleepy and 14 sleepier patients are shown in Table 1. There were no significant differences in age, BMI, sex

Discussion

The most important finding of our study was that in this group of 27 patients with HF and OSA, subjective daytime sleepiness assessed by the ESS score was inversely related to sympathetic activity quantified during wakefulness as MSNA burst incidence and burst frequency. Because multiunit MSNA is a reflection of nerve firing within a given cardiac cycle, the relationship between ESS and MSNA burst incidence was stronger because it excludes the confounding influence of heart rate. Differences in

Conclusions

In conclusion, our findings suggest that for a given severity of OSA in patients with HF, higher SNA counteracts the sleepiness-inducing effects of apnea-related hypoxia and sleep disruption. This raises the important question: What are the indications for treating OSA in patients with HF? EDS is the main indication for therapy of OSA in patients with and without HF because it has been shown in randomized trials that treating patients with OSA and an ESS score > 10 reduces sleepiness and

Acknowledgments

Author contributions: Dr Taranto Montemurro: contributed to the study design, data collection, data analysis and interpretation, and drafting and review of the manuscript for important intellectual content.

Dr Floras: contributed to the data analysis and interpretation, and drafting and review of the manuscript for important intellectual content.

Dr Millar: contributed to the data collection and review of the manuscript.

Dr Kasai: contributed to the data collection and review of the manuscript.

Mr

References (34)

  • A Rao et al.

    Sleep-disordered breathing in a general heart failure population: relationships to neurohumoral activation and subjective symptoms

    J Sleep Res

    (2006)
  • K Narkiewicz et al.

    Sympathetic activity in obese subjects with and without obstructive sleep apnea

    Circulation

    (1998)
  • VK Somers et al.

    Sympathetic neural mechanisms in obstructive sleep apnea

    J Clin Invest

    (1995)
  • ER Azevedo et al.

    Nonselective versus selective beta-adrenergic receptor blockade in congestive heart failure: differential effects on sympathetic activity

    Circulation

    (2001)
  • TD Bradley et al.

    Augmented sympathetic neural response to simulated obstructive apnoea in human heart failure

    Clin Sci (Lond)

    (2003)
  • RL Horner et al.

    Immediate effects of arousal from sleep on cardiac autonomic outflow in the absence of breathing in dogs

    J Appl Physiol

    (1995)
  • J Spaak et al.

    Muscle sympathetic nerve activity during wakefulness in heart failure patients with and without sleep apnea

    Hypertension

    (2005)
  • Cited by (0)

    Funding/Support: This study was supported by the Canadian Institute of Health Research [operating grant MOP-82731], and by the Heart and Stroke Foundation of Canada, the Canada Foundation for Innovation, the Ontario Innovation Trust, and the Ministry of Research and Innovation.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

    View full text