A community-based study of seasonal variation in the onset of chronic fatigue syndrome and idiopathic chronic fatigue

A comparison of health status in patients meeting alternative definitions for chronic fatigue syndrome/myalgic encephalomyelitis

BACKGROUND

Several diagnostic definitions are available for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME) that varies significantly in their symptom criteria. This pilot study was conducted to determine whether simple biological and clinical measures differed between CFS/ME patients meeting the 1994 Centres for Disease Control and Prevention (CDC) criteria, the International Consensus Criteria (ICC), as well as healthy controls.

METHODS

A total of 45 CFS/ME patients and 30 healthy controls from the South East Queensland region of Australia provided a blood sample, reported on their current symptoms, as well as aspects of their physical and social health using the Short-Form Health Survey (SF-36), and the World Health Organisation Disability Adjustment Schedule 2.0 (WHO DAS 2.0). Differences were examined using independent sample t-testing.

RESULTS

Patients fulfilling the ICC definition reported significantly lower scores (p < 0.05) for physical functioning, physical role, bodily pain, and social functioning than those that only fulfilled the 1994 CDC definition. ICC patients reported significantly greater (p < 0.05) disability across all domains of the WHO DAS 2.0.

CONCLUSIONS

These preliminary findings suggest that the ICC identifies a distinct subgroup found within patients complying with the 1994 CDC definition, with more severe impairment to their physical and social functioning.

The adoption of chronic fatigue syndrome/myalgic encephalomyelitis case definitions to assess prevalence: a systematic review

PURPOSE

Prevalence estimates have been based on several case definitions of chronic fatigue syndrome (CFS). The purpose of this work is to provide a rigorous overview of their application in prevalence research.

METHODS

A systematic review of primary studies reporting the prevalence of CFS since 1990 was conducted. Studies were summarized according to study design, prevalence estimates, and case definition used to ascertain cases.

RESULTS

Thirty-one studies were retrieved, and eight different case definitions were found. Early estimates of CFS prevalence were based on the 1988 Centers for Disease Control and Prevention, Australian, and Oxford. The 1994 Centers for Disease Control and Prevention, however, has been adopted internationally, as a general standard. Only one study has reported prevalence according to the more recent, Canadian Consensus Criteria. Additional estimates were also found according to definitions by Ho-Yen, the 2005 Centers for Disease Control and Prevention empirical definition, and an epidemiological case definition.

CONCLUSIONS

Advances in clinical case definitions during the past 10 years such as the Canadian Consensus Criteria have received little attention in prevalence research. Future assessments of prevalence should consider adopting more recent developments, such as the newly available International Consensus Criteria. This move could improve the surveillance of more specific cases found within CFS.

A review of the definitional criteria for chronic fatigue syndrome

RATIONALE, AIMS AND OBJECTIVES

The research community has for more than three decades tried to unravel the diagnostic mystery that is Chronic Fatigue Syndrome (CFS). This has resulted in considerable amounts of time and money being invested in attempts aimed at establishing the aetiology and pathogenesis of CFS. All of this investment has produced evidence of an interesting variety of endocrine, immune, infectious, muscular and neurological abnormalities in CFS; however, the cause remains elusive. The absence of a known causative agent or diagnostic test for CFS has resulted in the development of a number of CFS case definitions. As such, the main objectives of this paper are to provide a critical review of the similarities and differences between the varying approaches to CFS case definition. The conflicts and controversies that have emerged as a result of the differing definitional criterion for CFS are highlighted and the potential impact on future research is identified.

METHODS, RESULTS AND CONCLUSIONS

This paper presents a critical review of the most frequently used case definitions in CFS. There are currently five case definitions of CFS; however, the most prominent and widely used of these definitions is the 1994 Centre for Disease Control and Prevention Case Definitions. However, the pre-eminence of this definition over the others has never been substantiated and it has been widely criticized for its lack of specificity. Furthermore, none of the above case definitions have produced evidence to demonstrate their accuracy or precision at defining cases of CFS. A summary description of the symptom profile included in each of the case definitions is provided. The inconsistencies that have emerged in CFS research as a consequence of differing approaches to case definition are also highlighted and discussed.

Cortisol secretion and fatigue: associations in a community based cohort

The association between fatigue and reduced activity in the hypothalamo-pituitary-adrenal (HPA) axis has been described. However the temporal association between fatigue and HPA activity is under debate. We examine whether alterations in cortisol secretion play a role in the development of fatigue or whether changes occur later as a consequence of fatigue in a longitudinal cohort study of 4299 community dwelling adults (mean age 61). Cortisol secretion was measured from saliva samples collected waking, waking + 0.5, 2.5, 8, 12 h and bedtime at phase 7 (2003-2004) of the Whitehall II study. Fatigue was measured at phase 6 (2001), phase 7 and phase 8 (2006) of the Whitehall II study. Three elements of secretion were examined: waking cortisol, the cortisol awakening response and diurnal slope in cortisol secretion. Fatigue was determined using the vitality sub-scale of the Short Form-36. A wide variety of co-variates were measured. We find that fatigue measured at phase 6 was not associated with cortisol secretion at phase 7. At phase 7, low waking cortisol levels and a flat slope in diurnal cortisol secretion were associated with fatigue independently of co-variates. In participants low or free of fatigue at phase 7 low waking cortisol and flatter slope in cortisol secretion were associated with new-onset fatigue at phase 8 (for example, odds ratio for lowest vs. highest tertile of waking cortisol 1.50; 95% confidence intervals, 1.08, 2.09 after adjusting for all co-variates). In conclusion, we find that low waking salivary cortisol and a flat slope in cortisol secretion is associated with fatigue. Cortisol is also associated with future onset of fatigue suggesting that changes in cortisol secretion are etiologic or occur early in the genesis of fatigue.

Cortisol and severe fatigue: a longitudinal study in adolescent girls

Fatigue is a common complaint among adolescents, especially in girls, and is associated with high rates of school absenteeism. Severe fatigue is often accompanied by psychological and physical symptoms. In the chronic fatigue syndrome (CFS) functioning of the hypothalamic-pituitary-adrenal (HPA)-axis has previously been found to be altered. The aim of the present study was to investigate whether cortisol production is deviant in fatigued adolescent girls from the general population and to study longitudinal changes in fatigue in association with possible changes in HPA-axis functioning. In the cross-sectional part of the study the cortisol response to awakening (CAR) and to a low-dose oral dexamethasone were examined in a group of fatigued adolescent girls (n=87) in comparison to a non-fatigued control group (n=77). Questionnaires regarding fatigue, depression, anxiety, sleep quality, somatic symptoms and CFS-related symptoms were filled out. Follow up measurements were performed after 6 and 12 months. While the fatigued and non-fatigued group differed remarkably on all symptom self-reports, no differences between groups in CAR and response to dexamethasone were observed. Girls in the fatigued group remained fatigued over time and reported high levels of other psychological and physical symptoms during the whole year of the study. The CAR varied between time points but correlated non-systematically with situational characteristics or symptom reports. We conclude that trait-like fatigue, as measured in a sample of adolescent girls from a high school population, is not reflected in a dysregulation as assessed on the level of salivary cortisol after awakening.

Chronic fatigue syndrome: the need for subtypes

Chronic fatigue syndrome (CFS) is an important condition confronting patients, clinicians, and researchers. This article provides information concerning the need for appropriate diagnosis of CFS subtypes. We first review findings suggesting that CFS is best conceptualized as a separate diagnostic entity rather than as part of a unitary model of functional somatic distress. Next, research involving the case definitions of CFS is reviewed. Findings suggest that whether a broad or more conservative case definition is employed, and whether clinic or community samples are recruited, these decisions will have a major influence in the types of patients selected. Review of further findings suggests that subtyping individuals with CFS on sociodemographic, functional disability, viral, immune, neuroendocrine, neurology, autonomic, and genetic biomarkers can provide clarification for researchers and clinicians who encounter CFS' characteristically confusing heterogeneous symptom profiles. Treatment studies that incorporate subtypes might be particularly helpful in better understanding the pathophysiology of CFS. This review suggests that there is a need for greater diagnostic clarity, and this might be accomplished by subgroups that integrate multiple variables including those in cognitive, emotional, and biological domains.