ABSTRACT
BACKGROUND: To describe the association between body mass index (BMI) and a positive response during a head-up tilt test (HUT) in patients referred for an investigation of syncope. METHODS: Observational study of patients referred for the diagnostic evaluation of syncope. Patients were divided into four groups according to their BMI: <18.5 kg/m(2), 18.5-24.9 kg/m(2), 25-29.9 kg/m(2), and > 30 kg/m(2). RESULTS: A total of 419 patients were evaluated. The mean age was 43 ± 22 years, and 62% were female. The prevalence of a positive tilt test was different between groups when stratified by BMI (P = 0.01), with a higher proportion of patients with positive tests among those with BMI <18.5 kg/m(2) compared with other groups (P = 0.05). Multivariate analysis also showed that underweight patients had a 3.9 times higher risk for a positive HUT response (P = 0.01); additionally, the use of contraceptive drugs was associated with a protective effect during HUT (odds ratio: 0.35, confidence interval: 0.19-0.45, P = 0.001). CONCLUSION: In our sample, changes in BMI are associated with a positive response for HUT, and oral contraceptives seemed to protect against this response. Further studies are needed with larger numbers of patients to corroborate this finding.
