Neurally mediated hypotension in fatigued Gulf War veterans: a preliminary report

Medical Correlates of Chronic Multisymptom Illness in Gulf War Veterans

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Dynamic cerebral autoregulation is impaired in Veterans with Gulf War Illness: A case-control study

Neurological dysfunction has been reported in Gulf War Illness (GWI), including abnormal cerebral blood flow (CBF) responses to physostigmine challenge. However, it is unclear whether the CBF response to normal physiological challenges and regulation is similarly dysfunctional. The goal of the present study was to evaluate the CBF velocity response to orthostatic stress (i.e., sit-to-stand maneuver) and increased fractional concentration of carbon dioxide. 23 cases of GWI (GWI+) and 9 controls (GWI) volunteered for this study. Primary variables of interest included an index of dynamic autoregulation and cerebrovascular reactivity. Dynamic autoregulation was significantly lower in GWI+ than GWI- both for autoregulatory index (2.99±1.5 vs 4.50±1.5, p = 0.017). In addition, we observed greater decreases in CBF velocity both at the nadir after standing (-18.5±6.0 vs -9.8±4.9%, p = 0.001) and during steady state standing (-5.7±7.1 vs -1.8±3.2%, p = 0.042). In contrast, cerebrovascular reactivity was not different between groups. In our sample of Veterans with GWI, dynamic autoregulation was impaired and consistent with greater cerebral hypoperfusion when standing. This reduced CBF may contribute to cognitive difficulties in these Veterans when upright.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-Metabolic Disease or Disturbed Homeostasis due to Focal Inflammation in the Hypothalamus?

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease characterized by debilitating fatigue, lasting for at least 6 months, with associated malaise, headaches, sleep disturbance, and cognitive impairment, which severely impacts quality of life. A significant percentage of ME/CFS patients remain undiagnosed, mainly due to the complexity of the disease and the lack of reliable objective biomarkers. ME/CFS patients display decreased metabolism and the severity of symptoms appears to be directly correlated to the degree of metabolic reduction that may be unique to each individual patient. However, the precise pathogenesis is still unknown, preventing the development of effective treatments. The ME/CFS phenotype has been associated with abnormalities in energy metabolism, which are apparently due to mitochondrial dysfunction in the absence of mitochondrial diseases, resulting in reduced oxidative metabolism. Such mitochondria may be further contributing to the ME/CFS symptomatology by extracellular secretion of mitochondrial DNA, which could act as an innate pathogen and create an autoinflammatory state in the hypothalamus. We propose that stimulation of hypothalamic mast cells by environmental, neuroimmune, pathogenic and stress triggers activates microglia, leading to focal inflammation in the brain and disturbed homeostasis. This process could be targeted for the development of novel effective treatments.

[Role of the sympathetic nervous system in vasovagal syncope and rationale for beta-blockers and norepinephrine transporter inhibitors]

Vasovagal or neurocardiogenic syncope is a common clinical situation and, as with other entities associated with orthostatic intolerance, the underlying condition is a dysfunction of the autonomic nervous system. This article reviews various aspects of vasovagal syncope, including its relationship with orthostatic intolerance and the role of the autonomic nervous system in it. A brief history of the problem is given, as well as a description of how the names and associated concepts have evolved. The response of the sympathetic system to orthostatic stress, the physiology of the baroreflex system and the neurohumoral changes that occur with standing are analyzed. Evidence is presented of the involvement of the autonomic nervous system, including studies of heart rate variability, microneurography, cardiac innervation, and molecular genetic studies. Finally, we describe different studies on the use of beta-blockers and norepinephrine transporter inhibitors (sibutramine, reboxetine) and the rationality of their use to prevent this type of syncope.

Recent research on Gulf War illness and other health problems in veterans of the 1991 Gulf War: Effects of toxicant exposures during deployment

Veterans of Operation Desert Storm/Desert Shield - the 1991 Gulf War (GW) - are a unique population who returned from theater with multiple health complaints and disorders. Studies in the U.S. and elsewhere have consistently concluded that approximately 25-32% of this population suffers from a disorder characterized by symptoms that vary somewhat among individuals and include fatigue, headaches, cognitive dysfunction, musculoskeletal pain, and respiratory, gastrointestinal and dermatologic complaints. Gulf War illness (GWI) is the term used to describe this disorder. In addition, brain cancer occurs at increased rates in subgroups of GW veterans, as do neuropsychological and brain imaging abnormalities. Chemical exposures have become the focus of etiologic GWI research because nervous system symptoms are prominent and many neurotoxicants were present in theater, including organophosphates (OPs), carbamates, and other pesticides; sarin/cyclosarin nerve agents, and pyridostigmine bromide (PB) medications used as prophylaxis against chemical warfare attacks. Psychiatric etiologies have been ruled out. This paper reviews the recent literature on the health of 1991 GW veterans, focusing particularly on the central nervous system and on effects of toxicant exposures. In addition, it emphasizes research published since 2008, following on an exhaustive review that was published in that year that summarizes the prior literature (RACGWI, 2008). We conclude that exposure to pesticides and/or to PB are causally associated with GWI and the neurological dysfunction in GW veterans. Exposure to sarin and cyclosarin and to oil well fire emissions are also associated with neurologically based health effects, though their contribution to development of the disorder known as GWI is less clear. Gene-environment interactions are likely to have contributed to development of GWI in deployed veterans. The health consequences of chemical exposures in the GW and other conflicts have been called "toxic wounds" by veterans. This type of injury requires further study and concentrated treatment research efforts that may also benefit other occupational groups with similar exposure-related illnesses.

Plasma neuropeptide Y: a biomarker for symptom severity in chronic fatigue syndrome

BACKGROUND

Chronic fatigue syndrome (CFS) is a complex, multi-symptom illness with a multisystem pathogenesis involving alterations in the nervous, endocrine and immune systems.Abnormalities in stress responses have been identified as potential triggers or mediators of CFS symptoms. This study focused on the stress mediator neuropeptide Y (NPY). We hypothesized that NPY would be a useful biomarker for CFS.

METHODS

The CFS patients (n = 93) were from the Chronic Fatigue and Related Disorders Clinic at the University of Miami and met the 1994 case definition of Fukuda and colleagues. Healthy sedentary controls (n = 100)) were from NIH or VA funded studies. Another fatiguing, multi-symptom illness, Gulf War Illness (GWI), was also compared to CFS. We measured NPY in plasma using a radioimmunoassay (RIA). Psychometric measures, available for a subset of CFS patients included: Perceived Stress Scale, Profile of Mood States, ATQ Positive & Negative Self-Talk Scores, the COPE, the Beck Depression Inventory, Fatigue Symptom Inventory, Cognitive Capacity Screening Examination, Medical Outcomes Survey Short Form-36, and the Quality of Life Scale.

RESULTS

Plasma NPY was elevated in CFS subjects, compared to controls (p = .000) and to GWI cases (p = .000). Receiver operating characteristics (ROC) curve analyses indicated that the predictive ability of plasma NPY to distinguish CFS patients from healthy controls and from GWI was significantly better than chance alone. In 42 patients with CFS, plasma NPY had significant correlations (<0.05) with perceived stress, depression, anger/hostility, confusion, negative thoughts, positive thoughts, general health, and cognitive status. In each case the correlation (+ or -) was in the anticipated direction.

CONCLUSIONS

This study is the first in the CFS literature to report that plasma NPY is elevated compared to healthy controls and to a fatigued comparison group, GWI patients. The significant correlations of NPY with stress, negative mood, general health, depression and cognitive function strongly suggest that this peptide be considered as a biomarker to distinguish subsets of CFS.

Fatigue and autonomic dysfunction in non-alcoholic fatty liver disease

BACKGROUND

Fatigue is a significant symptom in nonalcoholic fatty liver disease (NAFLD) that impacts upon quality of life and is unrelated to liver disease severity. We examined the relationship between parameters of blood pressure regulation with perception of fatigue in NAFLD.

METHODS

Thirty-four non-diabetic subjects with histologically proven, non-cirrhotic NAFLD (26 [77%] males and 8 [23%] females) (mean +/- SD age 54 +/- 11) and 34 age, sex and BMI matched non-diabetic controls underwent subjective and objective evaluation of cardiovascular autonomic function (24 h blood pressure and head up tilt testing). All subjects completed the fatigue impact scale.

RESULTS

The NAFLD group had significantly higher autonomic symptom burden assessed using the orthostatic grading scale (OGS) compared to controls (4 +/- 4 vs. 1 +/- 2; p = 0.0003). Increasing orthostatic symptoms correlated with increasing fatigue (p = 0.006; r(2) = 0.3). Fatigue in NAFLD correlated inversely with 24 h measurement of systolic, diastolic and mean blood pressures (all p < 0.03; r(2) = 0.2). This relationship was predominantly related to lower blood pressure at night (p < 0.003; r(2) = 0.3). On head up tilt testing 57% of the NAFLD group had neurally-mediated hypotension (vasovagal syncope and/or orthostatic hypotension) (p = 0.006 compared to controls). The degree of blood pressure drop in response to standing correlated with fatigue severity (p = 0.008; r(2) = 0.3) and the autonomic symptom burden (OGS) (p = 0.03; r(2) = 0.2).

CONCLUSION

Autonomic symptoms are prevalent in NAFLD and associate with objective measures of autonomic dysfunction. Fatigue in NAFLD is associated with lower blood pressure and autonomic dysfunction. Studies are needed to determine whether this is a potential therapeutic target for fatigue in NAFLD.

Pituitary response to metyrapone in Gulf War veterans: relationship to deployment, PTSD and unexplained health symptoms

OBJECTIVE

Gulf War deployment has been associated with a distinct neuroendocrine profile characterized by low 24h basal ACTH levels and enhanced cortisol and ACTH suppression to low-dose dexamethasone. The metyrapone stimulation test was performed to further characterize hypothalamic-pituitary activity in Gulf War veterans (GWV) and its relationship to unexplained medical symptoms and post-traumatic stress disorder (PTSD).

METHOD

Eleven GWV without PTSD, 18 GWV with PTSD and 15 healthy subjects not exposed to the Gulf War theater (non-exposed) underwent the metyrapone stimulation test, which inhibits cortisol synthesis, impairs cortisol-mediated negative feedback inhibition and in turn increases levels of ACTH and 11-deoxycortisol, a cortisol precursor. These hormones were measured at baseline (7:00 a.m.) and at intervals (from 8:00 a.m. to 4:00 p.m.) following the administration of metyrapone 750mg orally at 7:05 a.m. and at 10:05 a.m.

RESULTS

There were group differences in the ACTH response despite similar cortisol and 11-deoxycortisol responses to metyrapone. GWV without PTSD had a significantly attenuated ACTH response compared to non-exposed subjects; GWV with PTSD had a significantly higher ACTH response than GWV without PTSD but did not differ from non-exposed subjects. Among GWV, unexplained medical health symptoms (e.g., neurological, musculoskeletal, cardiac, and pulmonary symptoms) and PTSD symptoms were significantly positively associated with the ACTH response to metyrapone.

CONCLUSION

Gulf War deployment is associated with a substantially lower ACTH response to metyrapone. In contrast, unexplained health symptoms and PTSD in Gulf War veterans are associated with relatively greater hypothalamic-pituitary activity which may reflect increased CRF activity and is evident only in consideration of deployment effects. This pattern of differences suggests either that Gulf War deployment and its associated exposures results in enduring changes in pituitary function or that reduced hypothalamic-pituitary activity protects against the development of PTSD and other deployment-related health problems.

Lower ambulatory blood pressure in chronic fatigue syndrome

OBJECTIVE

To examine blood pressure circadian rhythm in subjects with chronic fatigue syndrome (CFS) and appropriate normal and fatigued controls to correlate parameters of blood pressure regulation with perception of fatigue in an observational cohort study. The cause of CFS remains unknown and there are no effective treatments.

METHODS

To address whether inactivity was a confounder, we performed a 24-hour ambulatory blood pressure monitoring in the following three subject groups: 1) CFS patients (Fukuda Diagnostic criteria) (n = 38); 2) normal controls (n = 120); and 3) a fatigue comparison group (n = 47) with the autoimmune liver disease primary biliary cirrhosis (PBC). All patients completed a measure of fatigue severity (Fatigue Impact Scale). In view of the different demographics between the patient groups, patients were age- and sex-matched on a case-by-case basis to normal controls and blood pressure parameters were compared.

RESULTS

Compared with the control population, the CFS group had significantly lower systolic blood pressure (p < .0001) and mean arterial blood pressure (p = .0002) and exaggerated diurnal variation (p = .009). There was a significant inverse relationship between increasing fatigue and diurnal variation of blood pressure in both the CFS and PBC groups (p < .05).

CONCLUSION

Lower blood pressure and abnormal diurnal blood pressure regulation occur in patients with CFS. We would suggest the need for a randomized, placebo-controlled trial of agents to increase blood pressure such as midodrine in CFS patients with an autonomic phenotype.

Twenty-four hour plasma cortisol and adrenocorticotropic hormone in Gulf War veterans: relationships to posttraumatic stress disorder and health symptoms

BACKGROUND

We aim to characterize the baseline functioning of the hypothalamic-pituitary-adrenal (HPA) axis in Gulf War veterans (GWV) and examine the extent to which posttraumatic stress disorder (PTSD) and unexplained health symptoms-which commonly co-occur-have similar or different biological correlates.

METHODS

Thirty-one GWV, 20 with current PTSD and 11 without current or lifetime PTSD, and 16 healthy nondeployed subjects not exposed to the Gulf War theater underwent medical and psychiatric examination followed by blood sampling every half-hour over 24 hours for the measurement of cortisol and adrenocorticotropic hormone (ACTH).

RESULTS

Gulf War veterans without PTSD or another psychiatric disorder had significantly lower 24-hour plasma ACTH levels, a significantly higher cortisol:ACTH ratio, and no difference in cortisol levels compared to nondeployed subjects and to GWV with PTSD, controlling for body mass index (BMI). Among GWV, health symptoms (mood and cognitive symptoms) were positively associated with, and hyperarousal symptoms were negatively associated with, the cortisol:ACTH ratio. Additionally, the self-reported acute effects of pesticides and of pyridostigmine bromide during deployment were associated with lower ACTH levels, controlling for BMI and PTSD.

CONCLUSIONS

The data provide evidence of HPA axis dysregulation in Gulf War veterans, which may be related to Gulf War deployment exposures. Despite the overlap of chronic unexplained health symptoms and PTSD in GWV, these symptom constellations appear to be biologically distinct.

Orthostatic instability in a population-based study of chronic fatigue syndrome

PURPOSE

Autonomic nervous system dysfunction has been suggested as involved in the pathophysiology of chronic fatigue syndrome. This population-based case control study addressed the potential association between orthostatic instability (one sign of dysautonomia) and chronic fatigue syndrome.

SUBJECTS AND METHODS

Fifty-eight subjects who fulfilled criteria of the 1994 chronic fatigue syndrome research case definition and 55 healthy controls participated in a 2-day inpatient evaluation. Subjects had been identified during a 4-year population-based chronic fatigue syndrome surveillance study in Wichita, Kan. The present study evaluated subjects' current medical and psychiatric status, reviewed past medical/psychiatric history and medication use, used a stand-up test to screen for orthostatic instability, and conducted a head-up tilt table test to diagnose orthostatic instability.

RESULTS

No one manifested orthostatic instability in the stand-up test. The head-up tilt test elicited orthostatic instability in 30% of eligible chronic fatigue syndrome subjects (all with postural orthostatic tachycardia) and 48% of controls (50% with neurally mediated hypotension); intolerance was present in only nonfatigued (n=7) subjects. Neither fatigue nor illness severity were associated with outcome.

CONCLUSIONS

Orthostatic instability was similar in persons with chronic fatigue syndrome and nonfatigued controls subjects recruited from the general Wichita population. Delayed responses to head-up tilt tests were common and may reflect hydration status. These findings suggest reappraisal of primary dysautonomia as a factor in the pathogenesis of chronic fatigue syndrome.

Blunted circadian variation in autonomic regulation of sinus node function in veterans with Gulf War syndrome

PURPOSE

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.

CONCLUSION

Some symptoms of Gulf War syndrome may be due to subtle autonomic nervous system dysfunction.

Effects of posttraumatic stress disorder on cardiovascular stress responses in Gulf War veterans with fatiguing illness

Abnormal cardiovascular stress responses have been reported in Gulf War veterans with chronic fatigue. However, many of these veterans also suffer from posttraumatic stress disorder (PTSD), which could potentially explain the reported abnormalities. To test this hypothesis, 55 Gulf veterans (GVs) with chronic fatigue syndrome (CFS) or idiopathic chronic fatigue (ICF) were stratified into groups with (N=16) and without (N=39) comorbid PTSD, and were compared to healthy Gulf veterans (N=47) on cardiovascular responses to a series of stressors. The CFS/ICF with PTSD group had lower blood pressure responses to speech and arithmetic tasks, and more precipitous declines and slower recoveries in blood pressure after standing up than the controls. Similar trends in the CF/ICF group without PTSD were not significant, however. Both CFS/ICF groups had blunted increases in peripheral vascular resistance during mental tasks. However, only the veterans with comorbid PTSD had diminished cardiac output responses to the mental stressors and excessive vasodilatory responses to standing. Symptoms of posttraumatic stress were significant predictors of hypotensive postural responses, but only in veterans reporting a significant exposure to wartime stress. We conclude that comorbid PTSD contributes to dysregulation of cardiovascular responses to mental and postural stressors in Gulf veterans with medically unexplained fatiguing illness, and may provide a physiological basis for increased somatic complaints in Gulf veterans with symptoms of posttraumatic stress.