CLOCK and obstructive sleep apnea syndrome: Obstructive sleep apnea (OSA) is a chronic progressive disorder with high mortality and morbidity rate and is associated with cardiovascular diseases (CVD), including heart failure (HF).1 The physiopathological interaction between OSA and cardiovascular disease is complex and involves sympathetic activation, oxidative stress and inflammation, endothelial disfunction and disfunction of the Circadian clock gene.2-4