Uric acid excretion in North American and Southeast European children with obstructive sleep apnea.

Objective: Responses to nocturnal hypoxemia accompanying sleep-disordered breathing (SDB) may vary in different populations. Aims of this study were to (1) assess whether severity of SDB is related to uric acid excretion in North American and Southeast European children and (2) evaluate the interaction between nocturnal hypoxemia and country of children's origin in uric acid excretion.

Methods: Consecutive US and Greek children with snoring who were referred for polysomnography were recruited. Uric acid excretion expressed as uric acid-to-creatinine concentrations ratio in a morning urine specimen was the primary outcome measure.

Results: One hundred and twenty-six US children (6.8+/-0.7years old) and 123 Greek children (6.4+/-2.5years old) were recruited. Forty-three US and 53 Greek participants had moderate-to-severe nocturnal hypoxemia (SpO(2) nadir <90%). Obstructive apnea-hypopnea index and SpO(2) nadir were related to uric acid excretion in Greek (but not US) children after adjustment by age, gender and body mass index z-score (p<0.05). There was a significant interaction between severity of hypoxemia and country of children's origin in uric acid excretion after adjustment by age, gender and body mass index z-score (p=0.036). Greek children with moderate-to-severe hypoxemia had higher uric acid excretion (0.85+/-0.35) than those with mild/no hypoxemia (0.69+/-0.25) (p=0.005). US children with moderate-to-severe hypoxemia (0.41+/-0.20) did not differ in uric acid excretion from those with mild/no hypoxemia (0.42+/-0.22) (p=0.823).

Conclusions: Uric acid excretion differs in children with SDB and different ethnic backgrounds or environmental exposures.