Sleep syncope: important clinical associations with phobia and vagotonia

To compare demographic and clinical data from patients with sleep syncope to those of patients with "classical" vasovagal syncope [VVS] collected over the last 8 years.

Retrospective case-controlled study.

Syncope unit.

Fifty-four patients with a history suggestive of one or more episodes of sleep syncope (group SS) were matched for age and gender to 108 patients with VVS (control group). A syncope questionnaire was completed immediately before tilt-testing and included frequency, age-of-onset and severity of episodes; situations, postures and perceived triggers; lifetime prevalence of specific phobias; and symptoms during syncope.

Group SS were mainly women (65%), mean age of 46±2.1 years, with a mean lifetime total of 5.4±0.83 episodes of sleep syncope. Compared to controls, SS episodes were more likely to start in childhood, 26.9% versus 50% (p=0.005), and more severe, score 2.40±0.11 versus 2.81±0.15 (p=0.03). In group SS: syncope onset whilst lying down was more frequent, 4.6% versus 32.7% (p=0.001); the lifelong prevalence of any specific phobia was higher, 32.4% versus 74.5% (p=0.001), in particular blood injection injury (BII) phobia, 19.4% versus 57.4% (p=0.001); and during attacks, distressing vagal symptoms were more frequent, e.g., abdominal discomfort, 13.9% versus 72.2% (p=0.001).

Sleep syncope is not rare and is characterised by lifelong, intermittent but severe episodes of vasovagal syncope which may occur in the horizontal position, with distressing abdominal symptoms. BII phobia is strongly associated and may be a predisposing factor or a co-existent disorder in these patients.