People With Metabolic Syndrome & Obstruve Sleep Apnea Bear Higher Cardiovascular Risks

Thursday, September 2nd, 2010 at 5:38 PM

Metabolic syndrome (MetSyn) increases overall cardiovascular risk. MetSyn is also strongly associated with obstructive sleep apnea (OSA), and these 2 conditions share similar comorbidities.

Whether OSA increases cardiovascular risk in patients with the MetSyn has not been investigated.

Researchers examined how the presence of OSA in patients with MetSyn affected hemodynamic and autonomic variables associated with poor cardiovascular outcome.

This prospective clinical study involved 36 patients with MetSyn (ATP-III) divided into 2 groups matched for age and sex: (1) MetSyn+OSA (n = 18) and (2) MetSyn-OSA (n = 18).

OSA was defined by an apnea-hypopnea index (AHI) > 15 events/hour by polysomnography. The researchers recorded muscle sympathetic nerve activity (MSNA – microneurography), heart rate (HR), and blood pressure (BP – Finapres). Baroreflex sensitivity (BRS) was analyzed by spontaneous BP and HR fluctuations.

MSNA (34 ± 2 vs 28 ± 1 bursts/min, P = 0.02) and mean BP (111 ± 3 vs. 99 ± 2 mm Hg, P = 0.003) were higher in patients with MetSyn+OSA versus patients with MetSyn-OSA. Patients with MetSyn+OSA had lower spontaneous BRS for increases (7.6 ± 0.6 vs 12.2 ± 1.2 msec/mm Hg, P = 0.003) and decreases (7.2 ± 0.6 vs 11.9 ± 1.6 msec/mm Hg, P = 0.01) in BP.

MSNA was correlated with AHI (r = 0.48; P = 0.009) and minimum nocturnal oxygen saturation (r = -0.38, P = 0.04).

Patients with MetSyn and comorbid OSA have higher BP, higher sympathetic drive, and diminished BRS, compared with patients with MetSyn without OSA.

These adverse cardiovascular and autonomic consequences of OSA may be associated with poorer outcomes in these patients. Moreover, increased BP and sympathetic drive in patients with MetSyn+OSA may be linked, in part, to impairment of baroreflex gain.

Findings of this research study have been published in the journal SLEEP