Circadian rhythm in neurally mediated syncopal syndrome

We assessed daily distribution of the time of syncopal episodes in neurally mediated syncopal syndrome (NMS). The distribution of the episodes in vasovagal syncope (VVS) differed significantly from uniform occurrence (p<0.0001), with a primary morning peak (between 6 a.m. and noon) and secondary evening peak (between 6 p.m. and 9 p.m.). This morning peak was more prominent if excluded alcohol-related syncopes: 57% of total episodes occurred between 6 a.m. and noon. On the contrary, the majority of micturition syncope (91%) occurred in the evening, nighttime, or early morning (between 6 p.m. and 6 a.m.). In addition, 82% of the micturition syncopes related to alcohol intake. In conclusion, there are prominent circadian patterns in the occurrence of NMS: VVS shows a peak in the morning and micturition syncope tends to occur in the nighttime. Alcohol intake may influence the circadian pattern in NMS. Recognition of the daily distribution of NMS is helpful for patient education and therapeutic strategy.