Oxidative Stress and Sleep Apnoea in Clinically Healthy Infants in the First Year of Life

Summary Question of the study Respiratory instability as well as tissue damage by free radicals (oxidative stress) have been hypothesized to play a role in cases of sudden and unexpected infant death in the first year of life. The ratio of the oxidized/reduced form of redox compounds in the circulation could be used as a marker of oxidative stress. Therefore, the sleep apnoea rate and redox status of coenzyme Q10 (CoQ10) (percentage of the oxidized form in total CoQ10) were measured in a population of clinically healthy infants in their first year of life in order to study whether a physiological parameter of respiratory instability is related to a biochemical parameter of oxidative stress. Patients and methods Between May and December 1999, 323 infants in the first year of life were referred to a paediatric sleep laboratory. Sleep apnoea rate, periodic breathing and parameters of oxygenation (SaO2 and TcPO2) were calculated based on polysomnographic recordings. The CoQ10 redox status was calculated based on high‐pressure liquid chromatographic (HPLC) analysis. Results Statistical analysis showed an age‐dependent decrease in apnoea rate (r = – 0.38) and CoQ10 redox status (r = – 0.40). An increased CoQ10 redox status (median: 16.6 %; range: 7.3 – 29.7 %) was found in infants with high apnoea rates above the 90th percentile of a reference group in comparison with infants with apnoea rates below the 90th percentile of a reference group (median: 10.4 %; range: 5.1 – 20.4 %; P = 0.031). Conclusions These findings may indicate that high apnoea rates are accompanied by increased formation of free radicals in clinically healthy infants in the first year of life. Zusammenfassung Fragestellung Es wird vermutet, dass sowohl respiratorische Instabilität als auch Gewebeschädigung durch freie Radikale (oxidativer Stress) bei plötzlichen und unerwarteten Todesfällen im 1. Lebensjahr eine Rolle spielen. Das Verhältnis von oxidierter zu reduzierter Form der Redoxkomponenten im Blut wird als Marker für oxidativen Stress verwendet. Daher wurde die Schlafapnoerate und der Redoxstatus von Coenzym Q10 (CoQ10) (prozentualer Anteil der oxidierten Form am gesamten CoQ10) bei klinisch gesunden Säuglingen unter der Fragestellung gemessen, ob ein Zusammenhang zwischen physiolo­gischen Parametern der respiratorischen Instabilität und biochemischen Markern der oxidativen Schädigung besteht. Patienten und Methode Von Mai bis Dezember 1999 wurden 323 Säuglingen zur Durchführung eine