Relationship between serum substance P levels and daytime sleepiness in obstructive sleep apnea syndrome.
OBJECTIVE
We hypothesized that intermittent hypoxia might influence serum substance P levels, and that this effect might in turn contribute in excessive daytime sleepiness (EDS) in patients with obstructive sleep apnea syndrome (OSAS).


METHODS
Fifty-five patients with newly diagnosed OSAS and 15 age-matched nonapneic control subjects were enrolled in this study. Full polysomnography was performed in all patients. Single blood samples were drawn between 8:00 am and 9:00 am after the sleep study. Substance P levels were analyzed with a competitive enzyme immunoassay (substance P EIA kit; Cayman Chemical; Ann Arbor, MI).


RESULTS
There were no significant differences in age, gender, body mass index, smoking habit, and snoring between the two groups. Serum substance P levels in the OSAS group were significantly lower than that in the control group (p < 0.0001). Serum substance P levels were positively correlated with rapid eye movement sleep (r = 0.330, p = 0.049) and slow-wave sleep (r = 0.324, p = 0.049) phases. Serum substance P levels were negatively correlated with Epworth sleepiness scale score (r = - 0.253, p = 0.048), number of total apneas during the night (r = - 0.247, p = 0.036), number of respiratory events during the night (r = - 0.266, p = 0.024), apnea-hypopnea index (r = - 0.287, p = 0.015), respiratory arousal index (r = - 0.267, p = 0.026), time spent in apnea and hypopnea (r = - 0.307, p = 0.01), average oxygen desaturation (r = - 0.265, p = 0.026), and oxygen desaturation index (r = - 0.254, p = 0.031).


CONCLUSIONS
We concluded that EDS seen in some of the OSAS patients might be associated with various pathophysiologic mechanisms including substance P levels.
Ursavas
Ahmet
A
Department of Pulmonary Medicine, School of Medicine, University of Uludag, 16059 Görükle/Bursa, Turkey. ahmetursavas@gmail.com
Karadag
Mehmet
M
Ilcol
Yesim Ozarda
YO
Burgazlioglu
Basak
B
Ercan
Ilker
I
Gozu
R Oktay
RO
D020920:Dyssomnias / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D017286:Polysomnography; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D013373:Substance P / Q000097:blood* / Q000502:physiology
D013373:Substance P