NPPB and heart disorder: Second, NT-proBNP level depends on sex, age, and physiologic conditions such as renal function.44–46 We conducted sex-specific analyses because women had NT-proBNP levels that were approximately 1.4 times those of men in this study, as was the case in previous studies.44,45 The age-related increase in NT-proBNP may reflect the higher prevalence of subclinical cardiac disease and renal dysfunction in older subjects.47 Because NT-proBNP is mainly cleared by the kidneys, circulating levels are often elevated in patients with renal dysfunction.