title: Inverse relationship of subjective daytime sleepiness to sympathetic activity in patients with heart failure and obstructive sleep apnea.
abstract: 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 &lt; 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 &lt; .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.
authors.affiliation: Sleep Research Laboratory of the Toronto Rehabilitation Institute, Toronto, ON, Canada. Electronic address: taranto.luigi@gmail.com.
authors.forename: Luigi
authors.initials: L
authors.lastname: Taranto Montemurro
authors.affiliation: Department of Medicine of the University Health Network and Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: John S
authors.initials: JS
authors.lastname: Floras
authors.affiliation: Department of Medicine of the University Health Network and Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Millar
authors.affiliation: Sleep Research Laboratory of the Toronto Rehabilitation Institute, Toronto, ON, Canada.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kasai
authors.affiliation: Sleep Research Laboratory of the Toronto Rehabilitation Institute, Toronto, ON, Canada.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Gabriel
authors.affiliation: Department of Medicine of the University Health Network and Mount Sinai Hospital, Toronto, ON, Canada; Department of Clinical Sciences, Danderyd University Hospital, Karolinska Institutet, Danderyd, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Spaak
authors.affiliation: Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Fernando Morgadinho S
authors.initials: FMS
authors.lastname: Coelho
authors.affiliation: Sleep Research Laboratory of the Toronto Rehabilitation Institute, Toronto, ON, Canada; Department of Medicine of the University Health Network and Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: T Douglas
authors.initials: TD
authors.lastname: Bradley
mesh_terms: D006970:Disorders of Excessive Somnolence / Q000503:physiopathology*; D005260:Female; D006333:Heart Failure / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D017286:Polysomnography; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D018709:Statistics, Nonparametric; D013564:Sympathetic Nervous System / Q000503:physiopathology*