Association of obstructive sleep apnea with urinary albumin excretion in essential hypertension: a cross-sectional study.
BACKGROUND
Microalbuminuria reflects a state of widespread vascular dysfunction, whereas obstructive sleep apnea (OSA) further promotes atherosclerotic damage in hypertension.


METHODS
Cross-sectional.


METHODS
In an outpatient hypertensive unit, 62 untreated hypertensive patients (aged 48 +/- 7 years; office blood pressure [BP], 151 +/- 8/97 +/- 7 mm Hg) with OSA and 70 hypertensive patients without OSA (apnea hypopnea index [AHI] < or = 5) matched for age, sex, smoking status, body mass index, and 24-hour pulse pressure were studied.


METHODS
Hypertension and OSA compared with hypertension without OSA. OSA defined as AHI greater than 5, documented by polysomnography.


METHODS
Albuminuria assessed by urinary albumin-creatinine ratio (ACR).


METHODS
Participants underwent polysomnography, ambulatory BP monitoring, echocardiography, routine metabolic profile assessment, and glomerular filtration rate estimation, whereas ACR was measured from 2 nonconsecutive morning spot urine samples.


RESULTS
Hypertensive patients with OSA compared with those without OSA showed increased 24-hour diastolic BP (87 +/- 7 versus 85 +/- 7 mm Hg; P = 0.03) and nighttime pulse pressure (50 +/- 10 versus 45 +/- 10 mm Hg; P = 0.008), but did not differ regarding metabolic profile and estimated glomerular filtration rate. Albuminuria was greater by 57% in patients with OSA compared with those without OSA: log(10)ACR, 1.1 +/- 0.2 versus 0.7 +/- 0.4 mg/g; P < 0.001). In the entire study population, log10(ACR) correlated with log10(AHI) (r = 0.35; P < 0.001), minimum oxygen saturation during sleep (r = -0.33; P < 0.001), 24-hour pulse pressure (r = 0.38; P < 0.001), and nighttime pulse pressure (r = 0.21; P =0 .01). In a multivariable linear regression model, independent predictors of ACR were AHI (beta = 0.36; P < 0.001) and 24-hour pulse pressure (beta = 0.25; P = 0.01).


CONCLUSIONS
Cross-sectional study.


CONCLUSIONS
Albuminuria increases within the normal range in hypertensive individuals with OSA compared with those without OSA proportionally to OSA severity independently of confounders. The association of upper-airway dysfunction with albuminuria and pulsatile hemodynamic load may provide an explanatory mechanism for the OSA-related risk in hypertension.
Tsioufis
Costas
C
First Cardiology Clinic, University of Athens, Hippokration Hospital, Athens, Greece. ktsioufis@hippocratio.gr
Thomopoulos
Costas
C
Dimitriadis
Kyriakos
K
Amfilochiou
Anastasia
A
Tsiachris
Dimitris
D
Selima
Maria
M
Petras
Dimitris
D
Kallikazaros
Ioannis
I
Stefanadis
Christodoulos
C
D000328:Adult; D000419:Albuminuria / Q000150:complications* / Q000453:epidemiology / Q000652:urine; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D003430:Cross-Sectional Studies; D015716:Electrocardiography, Ambulatory; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications* / Q000453:epidemiology / Q000652:urine; D015994:Incidence; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D014481:United States / Q000453:epidemiology