NPPB and chronic obstructive pulmonary disease: Evidence of the inclusive effect of extrapulmonary comorbidities on physical activity in COPD patients is limited, with only a single comprehensive study using multiple regression analysis [17], in which the fibrinogen level, NT-proBNP level, and left ventricular diastolic dysfunction assessed by the deceleration time of the early transmitral flow and the systemic inflammation were reported to be extrapulmonary factors significantly affecting physical activity.