Effects of nocturnal intermittent hypoxia on metabolic syndrome in Japanese adults without abdominal obesity.

OBJECTIVES: The association between nocturnal intermittent hypoxia and metabolic syndrome (MetS) in individuals without abdominal obesity has not yet been fully explored. We conducted a longitudinal study to investigate the association between nocturnal intermittent hypoxia and the incidence of MetS and its components in Japanese individuals without abdominal obesity. METHODS: This prospective cohort study included 647 participants without baseline MetS and abdominal obesity, defined as a waist circumference of <90 cm in men and <80 cm in women. Nocturnal intermittent hypoxia was assessed using 3% oxygen desaturation index (ODI). MetS was diagnosed according to the modified National Cholesterol Education Program Adult Treatment Panel III criteria. Incident MetS and its components were assessed at the five-year follow-up survey. The median follow-up period was 5.0 years (IQR, 4.8-5.1). The association between nocturnal intermittent hypoxia and the incidence of MetS and its components was evaluated using a modified Poisson regression analysis. The analysis was stratified by age group (<65 years vs. ≥65 years). RESULTS: In the younger age group, 3% ODI ≥ 5 was associated with a significantly higher risk ratio (RR) for MetS incidence (RR 2.10, 95% confidence interval [CI]: 1.18-3.76). Participants with 3% ODI ≥ 5 in the younger age group also had significantly higher RRs for abdominal obesity (RR 2.17, 95% CI: 1.42-3.33), low high-density lipoprotein cholesterol (RR 2.01, 95% CI: 1.02-3.96), and hypertriglyceridemia (RR 2.41, 95% CI: 1.35-4.30). In the older age group, 3% ODI ≥ 5 was not significantly associated with increased RRs for MetS or its components. CONCLUSIONS: Nocturnal intermittent hypoxia was associated with an increased risk of developing MetS and some of its components in younger individuals without abdominal obesity.