Small urinary protein loss (low-grade albuminuria or microalbuminuria)
may reflect altered permeability of the glomerular filtration barrier.
In the present study, it was hypothesized that children with obstructive
sleep apnea have an increased risk of microalbuminuria compared with
control subjects without sleep-disordered breathing.
Albumin-to-creatinine ratio was measured in morning spot urine specimens
collected from consecutive children with or without snoring who were
referred for polysomnography. Three groups were studied: (i) control
subjects (no snoring, apneahypopnea index<1episodeh1; n=31); (ii) mild
obstructive sleep apnea (snoring, apneahypopnea index=15episodesh1;
n=71); and (iii) moderate-to-severe obstructive sleep apnea (snoring,
apneahypopnea index>5episodes.h1; n=27). Indications for polysomnography
in control subjects included nightmares, somnambulism and morning
headaches. An albumin-to-creatinine ratio>median value in the control
group (1.85mg of albumin per g of creatinine) was defined as elevated.
Logistic regression analysis revealed that children with
moderate-to-severe obstructive sleep apnea, but not those with mild
obstructive sleep apnea, had increased risk of elevated
albumin-to-creatinine ratio relative to controls (reference) after
adjustment for age, gender and presence of obesity: odds ratio 3.8 (95%
confidence interval 1.112.6); P=0.04 and 1.5 (0.63.7); 0.05,
respectively. Oxygen desaturation of hemoglobin and respiratory arousal
indices were significant predictors of albumin-to-creatinine ratio
(r=0.31, P=0.01; and r=0.43, P<0.01, respectively). In conclusion,
children with moderate-to-severe obstructive sleep apnea are at
significantly higher risk of increased low-grade excretion of albumin in
the morning urine as compared with control subjects without obstructive
sleep apnea. These findings may reflect altered permeability of the
glomerular filtration barrier related to nocturnal hypoxemia and
sympathetic activation which are induced by obstructive sleep apnea