Consequently, there was a significant interaction of ln BNP with sex and rhythm at blood collection (P for interaction = 0.011) as shown in Table 4: higher ln BNP was significantly associated with an increased risk of the recurrence of AF in a subgroup of male sex with sinus rhythm at blood collection (HR = 1.536, 95% CI = 1.095–2.154, P value = 0.013), but not in the other subgroups. Here, NPPB is linked to atrial fibrillation.