Nocturnal intermittent hypoxia and metabolic syndrome; the effect of being overweight: the CIRCS study.

Aim: We investigated whether nocturnal intermittent hypoxia, a surrogate marker for obstructive sleep apnea, is associated with metabolic syndrome and its components among Japanese.Methods: We examined 1,710 male and 2,896 female community-dwelling Japanese aged 40 to 69, who participated in annual cardiovascular examinations and investigations of sleep. Nocturnal intermittent hypoxia was estimated based on a 3% oxygen desaturation index measured with pulse-oximetry during sleep. No, mild and moderate-to-severe nocturnal intermittent hypoxia were defined by <5, 5 to <15 and ≥15 events/hour, respectively. Metabolic syndrome was defined by modified criteria of the Adult Treatment Panel III guidelines.Results: Compared with no nocturnal intermittent hypoxia, the multivariable odds ratio of metabolic syndrome was 1.9 (95% confidence interval: 1.6-2.4) for mild and 3.2 (2.2-4.7) for moderate-to-severe nocturnal intermittent hypoxia among men; 2.6 (2.1-3.4) and 5.8 (3.4-9.8) among women, respectively. When stratified by overweight status (body mass index ≥25 kg/m2), the multivariable odds ratio of two or more metabolic risk factors (other than overweight) associated with moderate-to-severe nocturnal intermittent hypoxia was 1.9 (1.2-3.1) among non-overweight subjects and 1.4 (0.9-2.1) among overweight subjects (p for interaction=0.002).Conclusions: Nocturnal intermittent hypoxia was associated with the accumulation of metabolic risk factors, especially among non-overweight individuals.