Relationship of daytime blood pressure and severity of obstructive sleep apnea among Chinese: a multi-center investigation in China.
BACKGROUND
Epidemiologic studies have shown an independent and definite association between obstructive sleep apnea (OSA) and hypertension. This study aimed to define the association between daytime blood pressure and severity of OSA in Chinese population in mainland of China.


METHODS
Twenty university hospital sleep centers in mainland of China were invited by the Chinese Medical Association (CMA) to participate in this epidemiologic study and 2297 consecutive patients (aged 18 - 85 years; 1981 males and 316 females) referred to these twenty sleep centers for evaluation of OSA between January 2004 and April 2006 were prospectively enrolled. Nocturnal polysomnography was performed in each patient, and disease severity was assessed based on the apneahypopnea index (AHI). These patients were classfied into four groups: nonapneic control (control, n = 257) with AHI < or = 5 episodes/hour; mild sleep apnea (mild, n = 402) with AHI > 5 and < or = 15 episodes/hour; moderate sleep apnea (moderate, n = 460) with AHI > 15 and < or = 30 episodes/hour and severe sleep apnea (severe, n = 1178) with AHI > 30 episodes/hour. Daytime blood pressure measurements were performed under standardized conditions in each patient at 10 a.m. in office on the day of referring to sleep centers for getting average value. All the patients were requested to quit medications related to blood pressure for three days before the day of assessing.


RESULTS
Both daytime systolic blood pressure and diastolic blood pressure values were significantly related to AHI positively (r = 0.201 and 0.276, respectively; both P values < 0.001) and to nadir nocturnal oxygen saturation negatively (r = -0.215 and -0.277, respectively; both P values < 0.001), which were the parameters of OSA severity. In two special designed mean plots, means of daytime systolic and diastolic blood pressure increased gradually with increasing AHI. Beyond AHI of 61 - 65, this increasing trend reached a plateau.


CONCLUSIONS
The results showed that OSA severity was associated with daytime blood pressure until AHI of 61 - 65, providing evidence for early OSA management, especially in OSA patients with concomitant hypertension.
He
Quan-ying
QY
Department of Respiratory Diseases, Beijing University People's Hospital, Beijing 100044, China.
Feng
Jing
J
Zhang
Xi-long
XL
Liang
Zong-an
ZA
Huang
Shao-guang
SG
Kang
Jian
J
Wang
Guang-fa
GF
Zhang
Li-qiang
LQ
Ma
Li-jun
LJ
Wang
Bei
B
Lin
Qi-chang
QC
Zhang
Jing-nong
JN
Liu
Hui-guo
HG
Luo
Yuan-ming
YM
Liu
Jian-hong
JH
Wang
Shi
S
Xiao
Gao-hui
GH
Lu
Gan
G
Zhang
Jin
J
Feng
Xue-wei
XW
Chen
Bao-yuan
BY
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology*; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020181:Sleep Apnea, Obstructive / Q000473:pathology*; D055815:Young Adult