Nocturnal intermittent hypoxia and C reactive protein among middle-aged community residents: a cross-sectional survey.
BACKGROUND
There are conflicting results for the association between obstructive sleep apnoea and raised C reactive protein (CRP) levels. A study was undertaken to investigate whether nocturnal intermittent hypoxia, a surrogate marker for obstructive sleep apnoea, was associated with CRP levels among a community-dwelling Japanese population.


METHODS
Among participants in the Circulatory Risk in Communities Study (CIRCS), 1422 male and 2466 female community residents aged 40-69 years were tested during sleep. No nocturnal intermittent hypoxia, mild nocturnal intermittent hypoxia and moderate to severe nocturnal intermittent hypoxia were defined using 3% oxygen desaturation index cut-off points at 5 and 15 events/h, respectively. High-sensitivity CRP levels were measured using a latex particle-enhanced immunonephelometric assay. Multivariate analysis was adjusted for age, sex, body mass index, smoking status, current alcohol intake, hypertension, hypercholesterolaemia, diabetes mellitus and menopausal status for women.


RESULTS
Multivariable-adjusted mean CRP levels among men were 0.70 mg/l (95% CI 0.65 to 0.75) for no nocturnal intermittent hypoxia, 0.82 mg/l (95% CI 0.74 to 0.89) for mild nocturnal intermittent hypoxia and 0.84 mg/l (95% CI 0.70 to 1.00) for moderate to severe nocturnal intermittent hypoxia (p for trend=0.03). The values for women were 0.59 mg/l (95% CI 0.57 to 0.62), 0.66 mg/l (95% CI 0.59 to 0.73) and 0.82 mg/l (95% CI 0.62 to 1.03), respectively (p for trend=0.008). Compared with no nocturnal intermittent hypoxia, the prevalence of a high CRP level (>or=1.0 mg/l) was 1.4-1.7-fold higher for mild to severe nocturnal intermittent hypoxia in both sexes.


CONCLUSIONS
Nocturnal intermittent hypoxia is associated with raised serum CRP levels among middle-aged Japanese subjects.
Public Health, Department of Social and Environmental Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Isao
I
Muraki
Takeshi
T
Tanigawa
Kazumasa
K
Yamagishi
Susumu
S
Sakurai
Tetsuya
T
Ohira
Hironori
H
Imano
Akihiko
A
Kitamura
Masahiko
M
Kiyama
Shinichi
S
Sato
Takashi
T
Shimamoto
Masamitsu
M
Konishi
Hiroyasu
H
Iso
D000328:Adult; D000368:Aged; D050197:Atherosclerosis / Q000097:blood / Q000209:etiology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D015986:Confounding Factors, Epidemiologic; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000150:complications
D015415:Biomarkers; D002097:C-Reactive Protein