Consequences of comorbid sleep apnea in the metabolic syndrome--implications for cardiovascular risk.
OBJECTIVE
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. We examined how the presence of OSA in patients with MetSyn affected hemodynamic and autonomic variables associated with poor cardiovascular outcome.


METHODS
Prospective clinical study.


METHODS
We studied 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).


METHODS
OSA was defined by an apnea-hypopnea index (AHI) > 15 events/hour by polysomnography. We 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.


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


CONCLUSIONS
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.
Trombetta
Ivani C
IC
Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
Somers
Virend K
VK
Maki-Nunes
Cristiane
C
Drager
Luciano F
LF
Toschi-Dias
Edgar
E
Alves
Maria Janieire N N
MJ
Fraga
Raffael F
RF
Rondon
Maria Urbana P B
MU
Bechara
Maíta G
MG
Lorenzi-Filho
Geraldo
G
Negrão
Carlos E
CE
D000328:Adult; D017704:Baroreflex; D001794:Blood Pressure; D002318:Cardiovascular Diseases / Q000209:etiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology*; D008875:Middle Aged; D010101:Oxygen Consumption; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology*; D014664:Vasodilation