RESUMO
BACKGROUND: Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) often present with a range of flu-like symptoms resembling sickness behavior as well as widespread pain and concentration deficits. The aim of this study was to explore the association between inflammatory markers previously shown to be related to fatigue severity in ME/CFS and common ME/CFS symptoms post-exertional fatigue, impaired cognitive processing, musculoskeletal pain and recurrent flu-like symptoms, and the moderating effect of sex on these associations. METHODS: 53 adult patients diagnosed with ME/CFS at a specialist clinic were included in the study. Fasting blood plasma was analyzed using the Olink Proseek Multiplex Inflammation panel (ß-NGF, CCL11, CXCL1, CXCL10, IL-6, IL-7, IL-8, IL-10, IL-18, TGF-α, TGF-ß-1 and SCF) and BioRad Human Cytokine Type 1 assay (TNF-α). Participants rated the average severity of symptoms (0-10) based on the 2011 International Consensus Criteria of ME/CFS during a structured clinical interview. Associations between inflammatory markers and symptom severity were analyzed using bivariate correlations and moderated regression analyses bootstrapped with 5000 repetitions. RESULTS AND CONCLUSIONS: Only ß-NGF was associated with the fatigue severity measure. However, higher levels of CCL11, CXCL10, IL-7, TNF-α and TGF-ß-1 were significantly associated with higher levels of impaired cognitive processing and musculoskeletal pain, and sex was a significant moderator for CXCL10, IL-7 and TGF-ß-1. Future studies should investigate the relationship between inflammatory markers and key symptoms in ME/CFS in a longitudinal design in order to explore if and for whom low-grade inflammation may contribute to illness development.
Assuntos
Síndrome de Fadiga Crônica/imunologia , Síndrome de Fadiga Crônica/fisiopatologia , Inflamação/sangue , Adulto , Biomarcadores/sangue , Estudos de Casos e Controles , Citocinas/sangue , Fadiga , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fator de Crescimento Neural/análise , Fator de Crescimento Neural/sangue , Índice de Gravidade de Doença , Fator de Necrose Tumoral alfa/sangueRESUMO
Background: Chronic sickness behavior is implicated in ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome) and chronic pain but the level of subjective sickness behavior in these conditions has not been investigated or compared to other clinical and non-clinical samples, or to the level in experimental inflammation. Furthermore, the relationship between sickness behavior and self-rated health and functioning is not known in patients with ME/CFS and chronic pain. The aim of the present study was to investigate how sickness behavior in patients with chronic conditions differs from that in individuals with experimental acute sickness, primary care patients, the general population and healthy subjects. In addition, we wanted to explore how sickness behavior is related to self-rated health and health-related functioning. Methods: Sickness behavior was quantified using the sickness questionnaire (SicknessQ). Self-ratings were collected at one time-point in 6 different samples. Levels of sickness behavior in patients with ME/CFS (n â= â38) and patients with chronic pain (n â= â190) were compared to healthy subjects with lipopolysaccharide(LPS)-induced inflammation (n â= â29), primary care patients (n â= â163), individuals from the general population (n â= â155) and healthy subjects (n â= â48), using linear regression. Correlations and moderated regression analyses were used to investigate associations between sickness behavior and self-rated health and health-related functioning in ME/CFS, chronic pain and the general population. Results: LPS-injected individuals (M â= â16.3), patients with ME/CFS (M â= â16.1), chronic pain (M â= â16.1) and primary care patients (M â= â10.7) reported significantly higher SicknessQ scores than individuals from the general population (M â= â5.4) and healthy subjects (M â= â3.6) all p's â< â0.001). In turn, LPS-injected individuals, patients with ME/CFS and chronic pain reported significantly higher SicknessQ scores than primary care patients (p's â< â0.01). Higher levels of sickness behavior were associated with poorer self-rated health and health-related functioning (p's â< â0.01), but less so in patients with ME/CFS and chronic pain than in individuals from the general population. Conclusions: Patients with ME/CFS and chronic pain report similar high levels of sickness behavior; higher than primary care patients, and comparable to levels in experimental inflammation. Further study of sickness behavior in ME/CFS and chronic pain populations is warranted as immune-to-brain interactions and sickness behavior may be of importance for functioning as well as in core pathophysiological processes in subsets of patients.
