Obstructive sleep apnoea as a risk factor for incident metabolic syndrome: a joined Episono and HypnoLaus prospective cohorts study

Cross-sectional studies have demonstrated that obstructive sleep apnoea (OSA) and metabolic syndrome (MetS) are often associated, but whether a temporal relationship exists is unknown. We aimed to investigate the effect of OSA on the risk of developing MetS in the general population. A prospective study was conducted combining two population-based samples: Episono (Brazil) and HypnoLaus (Switzerland). MetS was assessed according to unified criteria. Polysomnography (PSG) was performed at baseline and follow-up in Episono, and at baseline in HypnoLaus. OSA was defined according to the apnoea–hypopnoea index as mild (≥5–  −1 ) and moderate-to-severe (≥15 events·h −1 ). We included 1853 participants (mean±sd age 52±13 years, 56% female) without MetS at baseline. After mean±sd 6±1 years, 318 (17.2%) participants developed MetS. Moderate-to-severe OSA was independently associated with incident MetS (OR 2.58, 95% CI 1.61–4.11) and increased the number of MetS components from baseline to follow-up through mediation of the percentage of time with arterial oxygen saturation OSA is independently associated with an increased risk of developing MetS through mediation of nocturnal hypoxaemia in the general population.