Elevated nocturnal and morning blood pressure in patients with obstructive sleep apnea syndrome.
BACKGROUND
The nocturnal nondipping and elevated morning blood pressure (BP) in patients with obstructive sleep apnea syndrome (OSAS) have not yet been well investigated in Chinese patients. This study aimed to describe the BP profile, and to elucidate the relationships between daytime BP and nighttime BP, and between evening BP and morning BP in patients with OSAS.


METHODS
Twenty teaching hospital sleep centers in China were organized by the Chinese Medical Association to participate in this study and 2297 patients were recruited between January 2004 and April 2006. BP assessments were made at four time points (daytime, evening, nighttime and morning) and polysomnography (PSG) was performed and subjects were classified into four groups by their apnea-hypopnea index (AHI): control, n = 213 with AHI < 5; mild, n = 420 with AHI ≥ 5 and < 15; moderate, n = 460 with AHI ≥ 15 and < 30; and severe, n = 1204 with AHI ≥ 30. SPSS 11.5 software package was used for statistical analysis and figure drawing.


RESULTS
All the average daytime, nighttime, evening and morning BPs were positively correlated with AHI and negatively correlated with nadir nocturnal oxygen saturation. The ratios of nighttime/daytime and morning/evening average BP were positively correlated with AHI. The ratio of nighttime/daytime systolic BP became a "reversed BP dipping" pattern until the classification reached severe, while the ratio of nighttime/daytime diastolic BP became reversed at moderate. Similarly, the ratio of morning/evening diastolic BP becomes reversed even at mild.


CONCLUSIONS
OSAS may result in higher BP levels at all four time points. The ratios of nighttime/daytime and morning/evening BP increase with increased AHI. The increasing of diastolic BP, which is inclined to rise more quickly, is not parallel with increasing systolic BP.
Department of Respiratory Diseases, Peking University People's Hospital, Beijing 100044, China.
Quan-Ying
QY
He
Jing
J
Feng
Xi-Long
XL
Zhang
Zong-An
ZA
Liang
Shao-Guang
SG
Huang
Jian
J
Kang
Guang-Fa
GF
Wang
Li-Qiang
LQ
Zhang
Li-Jun
LJ
Ma
Bei
B
Wang
Qi-Chang
QC
Lin
Jin-Nong
JN
Zhang
Hui-Guo
HG
Liu
Yuan-Ming
YM
Luo
Jian-Hong
JH
Liu
Shi
S
Wang
Gao-Hui
GH
Xiao
Gan
G
Lu
Jin
J
Zhang
Xue-Wei
XW
Feng
Bao-Yuan
BY
Chen
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry; D001794:Blood Pressure / Q000502:physiology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D055815:Young Adult