Urinary 8-oxo-2’-deoxyguanosine is associated with respiratory-related arousal index: potential implications for screening obstructive sleep apnea as a preliminary study
Background: Obstructive sleep apnea (OSA) harms health and quality of life. Its high prevalence necessitates mass-screening. Intermittent hypoxia caused by pharyngeal stenosis or obstruction causes sleep fragmentation and leads to impaired vascular endothelial function and atherosclerosis, increasing the risk for cardiovascular disease. In patients with severe OSA (apnea-hypopnea index AHI ≧ 30 times/h), urinary 8-oxo-2’-deoxyguanosine (8-OHdG), an oxidative stress marker, is associated with respiratory-related markers of OSA, including AHI. Treatment with continuous positive airway pressure (CPAP) decreases urinary 8-OHdG and improves endothelial function. In patients with mild to moderate OSA (AHI 5-29 times/h), sleep fragmentation can lead to daytime sleepiness and impaired concentration, compromising work efficacy and road safety. CPAP can also decrease sleep fragmentation. Here we investigated the relationship between urinary 8-OHdG and sleep-related markers of OSA to clarify its usefulness as a screening tool. Methods: From 72 patients admitted to Kawasaki Medical School Hospital for polysomnography, the first urine sample in the morning following polysomnography was collected, and urinary 8-OHdG was measured by ELISA. Results: Urinary 8-OHdG differed significantly between subjects with a respiratory arousal index (RAI) of < 15 times/h and those with RAI ≧ 15 ( p = 0.046, 5.70 ± 2.84 vs 7.23 ± 3.52 ng/mg creatinine). The normal value of RAI is about 15 times/h in healthy adults aged in their 40s to 60s. The cut-off value was 4.03 ng/mg creatinine with respect to RAI ≧ 15 on the urinary 8-OHdG. Apart from sex ( p = 0.011) and body mass index ( p = 0.022), patient groups did not differ in age ( p = 0.201), smoking ( p = 0.857), alcohol consumption ( p = 0.511), hypertension ( p = 0.2), diabetes ( p = 0.366), or dyslipidemia ( p = 0.408). Conclusion: Urinary 8-OHdG significantly increased in OSA patients with RAI ≧ 15 times/h. This result suggests that combined with specific symptoms such as snoring and sleepiness, urinary 8-OHdG may be useful as a mass-screening tool not only for respiratory-related severe cases (AHI ≧ 30 times/h), but also for abnormal sleep-related cases.
