Vasovagal syncope in medical students and their first-degree relatives.

AIMS To determine the effect of family history on the likelihood of vasovagal syncope. METHODS AND RESULTS Sixty-two medical students and 228 first-degree relatives were studied. Vasovagal syncope was ascertained with the Calgary syncope symptom score. The effects of the sex of the subject and parental syncope history on the likelihood of offspring fainting were described using Kaplan-Meier estimates and analysed using proportional hazards regression. The prevalence of vasovagal syncope was 32% and the median age of first faint in those who fainted was 14 years. More females than males fainted [42 vs. 31%; P=0.02; hazard ratio (HR) 1.34 (95% CI 1.07-1.68)]. An individual with two fainting parents was more likely to faint than one with no fainting parents [P<0.0001; HR 3.4 (95% CI 1.7-7.03)]. In the proportional hazards model, offspring of either sex whose mother faints are more likely to faint than those whose mother does not faint [HR 2.86 (95% CI 1.54-5.31)]. Having a father who faints significantly increases the risk of syncope in sons [HR 4.12 (95%CI 1.39-12.31)], but not in daughters [HR 1.18 (95% CI 0.56-3.34)]. CONCLUSION Family history and sex of subject are important predictors of vasovagal syncope in offspring.