Blunted circadian variation in autonomic regulation of sinus node function in veterans with Gulf War syndrome.
OBJECTIVE
To test the hypothesis that subtle abnormalities of the autonomic nervous system underlie the chronic symptoms reported by many Gulf War veterans, such as chronic diarrhea, dizziness, fatigue, and sexual dysfunction.


METHODS
Twenty-two ill Gulf War veterans and 19 age-, sex-, and education-matched control veterans underwent measurement of circadian rhythm of heart rate variability by 24-hour electrocardiography, ambulatory blood pressure recording, Valsalva ratio testing, sympathetic skin response evaluation, sweat imprint testing, and polysomnography. Investigators were blinded to case- or control-group status.


RESULTS
High-frequency spectral power of heart rate variability increased normally 2.2-fold during sleep in controls but only 1.2-fold in ill veterans (P <0.0001). In ill veterans as compared with controls, it was lower at night (P = 0.0006), higher during the morning (P = 0.007), but no different during the rest of the day (P = 0.8). The mean heart rate of ill veterans also declined less at night (P = 0.0002), and their corrected QT intervals tended to be longer over the full 24 hours (P = 0.07), particularly at night (P = 0.03). Blunting of the nocturnal heart rate dip in ill veterans was confirmed by 24-hour automatic ambulatory blood pressure monitoring (P = 0.05) and polysomnography (P = 0.03). These differences remained significant after adjusting for potential confounders. Cases and controls were similar on measures of sympathetic adrenergic and sudomotor function, sleep architecture, respiratory function, and circadian variation in blood pressure and body temperature.


CONCLUSIONS
Some symptoms of Gulf War syndrome may be due to subtle autonomic nervous system dysfunction.
Haley
Robert W
RW
Divisions of Epidemiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8874, USA. Robert.Haley@UTSouthwestern.edu
Vongpatanasin
Wanpen
W
Wolfe
Gil I
GI
Bryan
Wilson W
WW
Armitage
Roseanne
R
Hoffmann
Robert F
RF
Petty
Frederick
F
Callahan
Timothy S
TS
Charuvastra
Elizabeth
E
Shell
William E
WE
Marshall
W Wesley
WW
Victor
Ronald G
RG
D000293:Adolescent; D000328:Adult; D001146:Arrhythmia, Sinus / Q000150:complications / Q000175:diagnosis; D001342:Autonomic Nervous System Diseases / Q000150:complications / Q000175:diagnosis; D018660:Blood Pressure Monitoring, Ambulatory; D001831:Body Temperature; D016022:Case-Control Studies; D021081:Chronobiology Disorders / Q000150:complications / Q000175:diagnosis; D015986:Confounding Factors, Epidemiologic; D015716:Electrocardiography, Ambulatory; D005712:Galvanic Skin Response; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D018923:Persian Gulf Syndrome / Q000150:complications / Q000175:diagnosis; D017286:Polysomnography; D016037:Single-Blind Method; D012893:Sleep Wake Disorders / Q000150:complications / Q000175:diagnosis; D013997:Time Factors; D014481:United States; D014636:Valsalva Maneuver; D014728:Veterans / Q000706:statistics & numerical data