Metabolic syndrome in obstructive sleep apnea and related cardiovascular risk

Background There is little evidence available about the relationship between metabolic syndrome as a comprehensive clinical entity and obstructive sleep apnea (OSA) with respect to the cardiovascular risk of patients with coexisting metabolic syndrome and OSA. Methods Eighty-nine consecutive patients (males 85%, aged 62 +/- 11 years) with newly-diagnosed OSA were evaluated for the presence of metabolic syndrome and the incidence of cardiovascular events after implementation of continuous positive airway pressure (CPAP) therapy was registered during medium-term follow-up. The diagnosis of OSA and metabolic syndrome was obtained by overnight polygraphy [with a presence of an apnea-hypopnea index (AHI) >= 15] and following NCEP ATP III recommendations, respectively. Results Forty-seven (53%) OSA patients had coexisting metabolic syndrome, with increased waist circumference (98%), high blood pressure (89%) and decreased high-density lipoprotein-cholesterol (83%) as the most frequent features. OSA patients with metabolic syndrome were also younger (58 +/- 11 years versus 65 +/- 4 years, P < 0.001) and presented an higher AHI (43.5 +/- 20.2 versus 34.8 +/- 17.3, P< 0.05) as compared to those without metabolic syndrome. Follow-up lasted 22 +/- 10 months. OSA patients who also presented metabolic syndrome suffered events less frequently compared to those who did not (6% versus 24%, P< 0.05), whereas the single end-points for follow-up (i.e. death, acute coronary syndrome, cerebrovascular event, peripheral vascular event, venous thromboembolism) did not significantly differ between the two groups. Conclusions Metabolic syndrome was a frequent comorbidity in OSA patients, reflecting higher degrees of sleep-disordered breathing, and did not increase the risk of cardiovascular events after adoption of CPAP therapy.