Etiology – Page 12 – American ME and CFS Society

What causes chronic fatigue?

Comment on:

Chronic fatigue syndrome comes out of the closet. [CMAJ. 1998]

Chronic fatigue syndrome or just plain tired? [CMAJ. 1998]

Chronic fatigue syndrome get court’s nod of approval as legitimate disorder. [CMAJ. 1998]

Even though the 3 articles on chronic fatigue syndrome 1–3 in the Sept. 8 issue commendably demolish the obsolete claim that chronic fatigue syndrome is a psychiatric illness, they also offer outdated biological explanations for the syndrome, namely, either a chronic viral infection or a weakened immune system. Although the first of these explanations seemed convincing until a few years ago, it is hardly tenable now, because no specific virus has been identified in these patients.4

You can read the rest of this comment here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1230107/pdf/cmaj_160_5_636.pdf

Source: Baschetti R. What causes chronic fatigue? CMAJ. 1999 Mar 9;160(5):636, 638. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1230107/pdf/cmaj_160_5_636.pdf (Full article)

Chronic fatigue syndrome among overseas development workers: A qualitative study

Abstract:

BACKGROUND: A relatively high proportion of overseas development workers may develop chronic fatigue syndrome (CFS). A qualitative study was conducted in order to investigate how such people perceived their condition.

METHODS: Twelve people who had developed CFS while working overseas with development organizations, or shortly after visiting development projects, were interviewed about their experiences. Their responses were analyzed using a grounded theory approach.

RESULTS: Most of the participants considered themselves to have been extremely healthy before they developed CFS. The syndrome did not appear to have been caused by depression. The symptoms which were reported covered the range of symptoms typically found in studies of CFS. Respondents described difficulty in receiving, and accepting, a diagnosis. All of the participants attributed the CFS to multiple causes, the principal causes being overwork, stress and infections. Among the consequences of CFS reported to be the most difficult were having to leave the development project prematurely; pain; powerlessness; loss of independence, and the unpredictability of CFS. Factors which had helped respondents cope with these difficulties included religious beliefs; comparisons with people who were worse off than they were; thinking about positive consequences of the condition, and talking with supportive people.

CONCLUSIONS: Some theories have suggested that CFS symptoms arise as a result of depression or other emotional difficulties, which the individual is not able to acknowledge. The results indicated that such theories may not apply to this subgroup of people with CFS. Further research on the etiology of CFS is warranted. Respondents described high levels of work-related stress as common to the experience of development work. It might be beneficial to train development workers in stress management techniques. Development organizations should be encouraged to ensure that their workers take sufficient time to rest, and attempts should be made to reduce work pressures.

Source: Lovell DM. Chronic fatigue syndrome among overseas development workers: A qualitative study. J Travel Med. 1999 Mar;6(1):16-23. http://jtm.oxfordjournals.org/content/6/1/16.long (Full article)

Incidence, risk and prognosis of acute and chronic fatigue syndromes and psychiatric disorders after glandular fever

Abstract:

BACKGROUND: The role of viruses in the aetiology of both chronic fatigue syndrome (CFS) and depressive illness is uncertain.

METHOD: A prospective cohort study of 250 primary care patients, presenting with glandular fever or an ordinary upper respiratory tract infection (URTI).

RESULTS: The incidence of an acute fatigue syndrome was 47% at onset, after glandular fever, compared with 20% with an ordinary URTI (relative risk 2.3, 95% CI 1.3-4.1). The acute fatigue syndrome lasted a median (interquartile range) of eight weeks (4-16) after glandular fever, but only three weeks (2-4) after an URTI. The prevalence of CFS was 9-22% six months after glandular fever, compared with 0-6% following an ordinary URTI, with relative risks of 2.7-5.1. The most conservative measure of the incidence of CFS was 9% after glandular fever, compared with no cases after an URTI. A conservative estimate is that glandular fever accounts for 3113 (95% CI 1698-4528) new cases of CFS per annum in England and Wales. New episodes of major depressive disorder were triggered by infection, especially the Epstein-Barr virus, but lasted a median of only three weeks. No psychiatric disorder was significantly more prevalent six months after onset than before.

CONCLUSIONS: Glandular fever is a significant risk factor for both acute and chronic fatigue syndromes. Transient new major depressive disorders occur close to onset, but are not related to any particular infection if they last more than a month.

Source: White PD, Thomas JM, Amess J, Crawford DH, Grover SA, Kangro HO, Clare AW. Incidence, risk and prognosis of acute and chronic fatigue syndromes and psychiatric disorders after glandular fever. Br J Psychiatry. 1998 Dec;173:475-81. http://www.ncbi.nlm.nih.gov/pubmed/9926075

Yersinia enterocolitica and the chronic fatigue syndrome

Abstract:

OBJECTIVES: To investigate the potential role of Yersinia enterocolitica in patients with chronic fatigue syndrome (CFS).

METHODS: An immunoblot technique was used to detect antibodies to various Yersinia outer membrane proteins (YOPs) in serum samples from 88 patients with CFS and 77 healthy neighbourhood controls, matched for gender and age.

RESULTS: The prevalence of IgG and IgA antibodies to various Yersinia outer membrane proteins (YOPs) did not differ between patients with CFS and healthy controls. Twenty-four patients (27%) and nineteen controls (25%) had IgG antibodies to one or more YOPs. Four patients and two controls had both serum IgG and IgA antibodies to at least two different YOPs, compatible with a recent or persistent infection. Although all patients with positive IgG and IgA reactions to two or more YOPs had symptoms that could point to persistent Yersinia infection, these symptoms were also found frequently in patients without antibodies to YOPs.

CONCLUSIONS: We conclude that Y. enterocolitica is unlikely to play a major role in the aetiology of CFS.

Source: Swanink CM, Stolk-Engelaar VM, van der Meer JW, Vercoulen JH, Bleijenberg G, Fennis JF, Galama JM, Hoogkamp-Korstanje JA. Yersinia enterocolitica and the chronic fatigue syndrome. J Infect. 1998 May;36(3):269-72. http://www.ncbi.nlm.nih.gov/pubmed/9661935

Demonstration on Borna disease virus in patients with chronic fatigue syndrome

Abstract:

Chronic fatigue syndrome (CFS), a recently named heterogeneous disorder, is an illness of unknown etiology. The association between CFS and several viral infection has been suggested. Here, we centered on the possible link between CFS and Borna disease virus (BDV) infection.

BDV is a neurotropic, nonsegmented negative-strand (NNS) RNA virus. Recent epidemiological data have suggested that BDV may be closely associated with depression and schizophrenia in humans.

In Japanese patients with CFS, the prevalence of BDV infection was 34% (30/89) and 12% (7/57) by immunoblotting and PCR analysis, respectively. Furthermore, anti-BDV antibodies and BDV RNA were detected in a family cluster with CFS. These results suggested that this virus contributes to or initiates CFS, although the single etiologic role of BDV is unlikely.

Source: Nakaya T, Kuratsune H, Kitani T, Ikuta K. Demonstration on Borna disease virus in patients with chronic fatigue syndrome. Nihon Rinsho. 1997 Nov;55(11):3064-71. [Article in Japanese] http://www.ncbi.nlm.nih.gov/pubmed/9396313

Chronic fatigue syndrome–aetiological aspects

Abstract:

The chronic fatigue syndrome (CFS) has been intensively studied over the last 40 years, but no conclusions have yet been agreed as to its cause. Most cases nowadays are sporadic. In the established chronic condition there are no consistently abnormal physical signs or abnormalities on laboratory investigation.

Many physicians remain convinced that the symptoms are psychological rather than physical in origin. This view is reinforced by the emotional way in which many patients present themselves. The overlap of symptoms between CFS and depression remains a source of confusion and difficulty. But even if all CFS patients were rediagnosed as depressives, this would not negate the possibility of an underlying organic cause for the condition, in view of the growing evidence that depression itself has a physical cause and responds best to physical treatments.

There is some evidence both for active viral infection and for an immunological disorder in the CFS. Many observations suggest that the syndrome could derive from residual damage to the reticular activating system (RAS) of the upper brain stem and/or to its cortical projections. Such damage could be produced by a previous viral infection, leaving functional defects unaccompanied by any gross histological changes.

In animal experiments activation of the RAS can change sleep state and activate or stimulate cortical functions. RAS lesions can produce somnolence and apathy. Studies by modern imaging techniques have not been entirely consistent, but many magnetic resonance imaging (MRI) studies already suggest that small discrete patchy brain stem and subcortical lesions can often be seen in CFS.

Regional blood flow studies by single photon-emission computerized tomography (SPECT) have been more consistent. They have revealed blood flow reductions in many regions, especially in the hind brain. Similar lesions have been reported after poliomyelitis and in multiple sclerosis–in both of which conditions chronic fatigue is characteristically present. In the well-known post-polio fatigue syndrome, lesions predominate in the RAS of the brain stem. If similar underlying lesions in the RAS can eventually be identified in CFS, the therapeutic target for CFS would be better defined than it is at present. A number of logical approaches to treatment can already be envisaged.

Comment in:

Chronic fatigue syndrome. [Eur J Clin Invest. 1997]

Source: Dickinson CJ. Chronic fatigue syndrome–aetiological aspects. Eur J Clin Invest. 1997 Apr;27(4):257-67. http://www.ncbi.nlm.nih.gov/pubmed/9134372

Precipitating factors for the chronic fatigue syndrome

Abstract:

The etiology of the Chronic Fatigue Syndrome (CFS) is unknown but it is usually considered to be postinfectious or postviral. Many infecting agents have been suspected as causative but none has been proven.

We investigated precipitating factors in 134 CFS patients through the use of a questionnaire, interview, clinical examination and serology for infecting agents; 35 healthy controls completed a similar questionnaire. CFS started with an apparently infectious illness in 96 (72%) but a definite infection was only found in seven of these 96 (7%). Thirty-eight (28%) had no apparent infectious onset: 15/38 (40%) had noninfectious precipitants (trauma, allergy, surgery).

There was no apparent precipitating event in 23/38 (61%). Immunization was not a significant precipitant. Stressful events were very common in the year preceding the onset of CFS (114/134, 85%) but these occurred in only 2/35 (6%) of the controls (p < .0001). The onset of CFS may be associated with preceding stressful events and multiple other precipitants. An infectious illness is not uniformly present at the onset and no single infectious agent has been found; CFS is most likely multifactorial in origin.

Source: Salit IE. Precipitating factors for the chronic fatigue syndrome. J Psychiatr Res. 1997 Jan-Feb;31(1):59-65. http://www.ncbi.nlm.nih.gov/pubmed/9201648

Postinfectious chronic fatigue: a distinct syndrome?

Abstract:

Chronic fatigue syndrome (CFS) is often preceded by a viral illness and has recurrent “flu-like” symptoms. We compared demographic, clinical, and laboratory features (markers of inflammation and viral infection) among 717 patients with chronic fatigue (CF) with and without a self-reported postinfectious onset to identify associated clinical and biologic findings and to examine the subset of patients with CFS. Only subjective fever, chills, sore throat, lymphadenopathy, poorer functional status, and attribution of illness to a physical condition were significantly associated with a postinfectious onset. The features of patients with CFS were virtually identical to those of the broader category of patients with CF. We conclude that a postinfectious onset was not associated with a pattern of abnormalities across multiple psychosocial and biologic parameters.

Source: Buchwald D, Umali J, Pearlman T, Kith P, Ashley R, Wener M. Postinfectious chronic fatigue: a distinct syndrome? Clin Infect Dis. 1996 Aug;23(2):385-7. http://cid.oxfordjournals.org/content/23/2/385.long (Full article)

A case-control study to assess possible triggers and cofactors in chronic fatigue syndrome

Abstract:

PURPOSE: To assess possible triggers and cofactors for chronic fatigue syndrome (CFS) and to compare levels of selected cytokines between cases and an appropriately matched control group.

PATIENTS AND METHODS: We conducted a case-control study of 47 cases of CFS obtained through a regional CFS research program maintained at a tertiary care medical center. One age-, gender-, and neighborhood-matched control was identified for each case through systematic community telephone sampling. Standardized questionnaires were administered to cases and controls. Sera were assayed for transforming growth factor-beta (TGF-beta), interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, and antibody to Borrelia burgdorferi and Babesia microti.

RESULTS: Cases were more likely to have exercised regularly before illness onset than controls (67% versus 40%; matched odds ratio (MOR) = 3.4; 95% CI = 1.2 to 11.8; P = 0.02). Female cases were more likely to be nulliparous prior to onset of CFS than controls (51% versus 31%; MOR = 8.0; 95% CI = 1.03 to 170; P = 0.05). History of other major factors, including silicone-gel breast implants (one female case and one female control), pre-morbid history of depression (15% of cases, 11% of controls) and history of allergies (66% of cases, 51% of controls) were similar for cases and controls. However, cases were more likely to have a diagnosis of depression subsequent to their diagnosis of CFS compared to a similar time frame for controls (MOR = undefined; 95% CI lower bound = 2.5; P < 0.001). Positive antibody titers to B burgdorferi (one case and one control) and B microti (zero cases and two controls) were also similar.

CONCLUSIONS: Further investigation into the role of prior routine exercise as a cofactor for CFS is warranted. This study supports the concurrence of CFS and depression, although pre-morbid history of depression was similar for both groups.

Comment in: Etiology of chronic fatigue syndrome. [Am J Med. 1997]

Source: MacDonald KL, Osterholm MT, LeDell KH, White KE, Schenck CH, Chao CC, Persing DH, Johnson RC, Barker JM, Peterson PK. A case-control study to assess possible triggers and cofactors in chronic fatigue syndrome. Am J Med. 1996 May;100(5):548-54. http://www.ncbi.nlm.nih.gov/pubmed/8644768

Demonstration of Borna disease virus RNA in peripheral blood mononuclear cells derived from Japanese patients with chronic fatigue syndrome

Abstract:

CFS, a recently named heterogeneous disorder, is an illness of unknown etiology. The association of CFS with viral infections has been suggested. A common association between CFS and several viruses examined has not been confirmed.

Here, we centered on the possible link between CFS and BDV infection. By nested RT-PCR followed by hybridization, BDV RNA was demonstrated as a clear signal in PBMCs in 3 out of 25 CFS patients. The amplified cDNA fragments were cloned and sequenced. A total of 16 clones were studied. Intra-patients divergencies of the p24 were 2-9%, 3-20%, and 3-11% in the deduced amino acids. Inter-patient divergencies among the 16 clones were 3-24%. Antibodies to recombinant BDV p24 protein were detected in 6 CFS patients including one carrying BDV RNA.

Overall, these gave the prevalence of 32% (8/25) in Japanese CFS patients, suggesting that Japanese CFS is highly associated with active infection of BDV, or a related agent.

Source: Nakaya T, Takahashi H, Nakamura Y, Asahi S, Tobiume M, Kuratsune H, Kitani T, Yamanishi K, Ikuta K. Demonstration of Borna disease virus RNA in peripheral blood mononuclear cells derived from Japanese patients with chronic fatigue syndrome. FEBS Lett. 1996 Jan 8;378(2):145-9. http://onlinelibrary.wiley.com/doi/10.1016/0014-5793(95)01439-X/epdf (Full article)