Sex Moderates the Relationship Between Nausea Severity and Heart Rate Variability in Adolescents and Young Adults

BACKGROUND: Nausea is a common complaint among children, and is particularly prevalent in children with functional abdominal pain (FAP), with nearly half of children with FAP also endorsing nausea. Dysfunction of the autonomic nervous system (ANS), which can be indexed by heart rate variability (HRV), leads to abnormalities in gastric electrical activity that are associated with GI symptoms. AIMS: To evaluate that relationship between nausea severity and HRV in adolescents and young adults with a history of FAP and to assess for sex differences. METHODS: Participants were pediatric patients with a diagnosis of FAP who were recruited from a pediatric GI clinic between 1993 and 2007 for a prospective study of the course of FAP. Study analyses focused on the cross-sectional relationship between HRV, indexed by standard deviation of the R-R interval (SDRRI) and high frequency (HF) power, and nausea severity collected during a follow-up visit in late adolescence and young adulthood. RESULTS: Controlling for age and BMI, a significant nausea by sex interaction emerged for both SDRRI and HF power. Tests of conditional effects of nausea by sex showed that the inverse relation between nausea severity and both SDRRI and HF was significant for females but not for males. CONCLUSIONS: This is the first study to evaluate the relationship between nausea severity and HRV. Greater nausea severity was associated with lower HRV in females but not in males. Further validation of these results may provide insight into novel treatment approaches for females with nausea that target vagal tone.