The relationship between Gulf War Illness symptom severity and heart rate variability: A pilot study.

Introduction: Gulf War Illness (GWI) is a chronic multisymptom illness affecting 250,000+ veterans of the '90-'91 Gulf War which remains under-explored in terms of its physiological characteristics. We investigated whether subjective GWI symptom severity scores were related to objective measures of autonomic nervous system activity.

Methods: We estimated activity in the two major branches of the autonomic nervous system (the parasympathetic nervous system [PNS] and the sympathetic nervous system [SNS]) via metrics of heart rate variability in a sample of Veterans who met established criteria for GWI with varying degrees of self-reported symptom severity.