NPPB and obstructive sleep apnea syndrome: In the OSA group, NT-proBNP serum levels were positively associated with age (r = 0.350, p = 0.001) and percentage of time with oxyhemoglobin saturation < 90% during sleep (r = 0.357, p = 0.009), while they were negatively associated with average (r = −0.403, p = 0.003) and minimum (r = −0.332, p = 0.015) oxyhemoglobin saturation during sleep.