Chronic fatigue syndrome (CFS) is a disabling condition that seriously affects school-attendance and social activities
]. The prevalence among 8–17 years olds has been reported as high as 1%
]; thus, CFS constitutes a substantial health problem in adolescence. As yet, no effective pharmacotherapy exists.
CFS patients report a great variety of bodily symptoms. Generally, their experience of overwhelming fatigue is assumed to be the single most important factor for their substantial impairments. However, it is conceivable that other symptoms might equally impact on their abilities. If so, this might be important for clinical management and suggest alternative treatment strategies. The relationship between symptoms and disability has rarely been explored in previous CFS reports.
Certain characteristic CFS symptoms, such as lightheadedness, indicate alterations of autonomic nervous activity. Indeed, experimental studies have demonstrated distinct abnormalities in cardiovascular autonomic control
]. Previous reports from our institution have documented higher blood pressure and heart rate at rest among adolescent CFS patients as compared to healthy controls and a stronger increase of these variables upon orthostatic stress
]. Similarly, ambulatory measurements of blood pressure and heart rate indicate higher nocturnal values among CFS patients as compared to controls
]. Taken together, these studies suggest that abnormal autonomic nervous activity might constitute an important aspect of CFS pathophysiology
]. If so, a relationship between clinical symptoms and indices of altered autonomic cardiovascular control should be demonstrable, which in turn might provide a basis for development of novel therapies as well as a diagnostic test.
As yet, no CFS biomarker has any diagnostic utility; thus, the diagnosis is solely based upon patients’ reports of symptoms. Several different case definitions exist, reflecting unsettled controversies in the scientific community
]. The definition from the International Chronic Fatigue Syndrome Study Group at the Centers for Disease Control and Prevention (commonly referred to as the CDC-definition) appears to be most frequently used
]. This definition requires at least six months of unexplained chronic or relapsing fatigue of new onset, severely affecting daily activities, as well as four or more of eight specific accompanying symptoms (headache, muscle pain, joint pain, sore throat, tender lymph nodes, impaired memory or concentration, unrefreshing sleep, and malaise after exertion). The validity of this definition has been questioned
]. For instance, a formal factor analysis of symptoms in a broadly defined group of chronic fatigued patients did not show a strong correspondence with the CDC accompanying symptoms
]. Accordingly, a recent study by Sullivan and co-workers based upon the Swedish twin registry concluded that there was no empirical support for the requirement of four out of eight CDC accompanying symptoms
]. In adolescents, few studies of validity have been conducted. Thus, one purpose of this study is to explore the informative value of the CDC-definition within a more broadly defined population of adolescent chronic fatigue sufferers; this approach has been recommended by others
In 2007, we launched an observational prospective study on the clinical course of adolescent CFS. The changes of different clinical features with time have been reported elsewhere
]. However, little is known about the interrelation of pathophysiological characteristics, patients’ experiences, and functional abilities. Thus, the overall aim of the present report is to explore the relationship between indices of autonomic cardiovascular control, the CDC case definition, important clinical symptoms, and disability in adolescent chronic fatigue syndrome at a single time point.