Medical Correlates of Chronic Multisymptom Illness in Gulf War Veterans

Chronic multisymptom illness (CMI) is more prevalent among deployed than nondeployed veterans from the first Gulf War. Objective physiologic markers of CMI are lacking. The purpose of this study is to determine whether measurable abnormalities in the autonomic nervous system or hypothalamic-pituitary adrenal axis would distinguish CMI cases (CMI+) from controls (CMI-) among deployed veterans of the 1990-1991 Gulf War.

This is a cross-sectional case-control cohort study that examined deployed veterans who participated in the Phase III study: National Health Survey of Gulf War Veterans and Their Families. Autonomic nervous system and hypothalamic-pituitary adrenal axis function-related measures included: 24-hour heart-rate variability, urinary catecholamines and cortisol, hypertension, insulin sensitivity, dyslipidemia, body fat, bone mineral density, and ultrasensitive C-reactive protein.

Veterans of the first Gulf War with CMI (n = 73) and without the condition (n = 111) were studied. Sociodemographic characteristics were similar. Veterans with CMI reported poorer mental and physical functioning, greater use of prescription medications, and more nonroutine clinic visits. These veterans were also more likely to have fibromyalgia syndrome, irritable bowel syndrome, metabolic syndrome, and among males, a larger waist-to-hip ratio. Lower values for a nonlinear heart-rate-variability parameter-the short-term fractal scaling exponent (DFA1), reflecting an increased randomness of beat-to-beat changes in heart rate-were observed in veterans with CMI than those veterans without it (1.28±0.16vs 1.35±0.15; p=0.005). Hypothalamic-pituitary-adrenal axis function measures were similar between the two groups.

In this cohort of deployed veterans from the first Gulf War, we identified abnormal heart-rate variability in veterans with CMI compared to veterans without the condition, which suggests abnormal functioning of the autonomic nervous system and possible long-term cardiovascular effects.