A pathophysiological approach to chronic fatigue syndrome: Investigation of changes in exercise capacity, muscle strength and autonomic nervous system, and differences in blood adropin levels in patients with chronic fatigue syndrome compared to healthy controls

Objective: Chronic Fatigue Syndrome (CFS) is a complex syndrome characterized by fatigue lasting at least six months, with no explainable cause, accompanied by symptoms such as musculoskeletal pain, cognitive issues, sleep problems, autonomic dysfunction, and post-exertional malaise. This thesis aims to evaluate all these systems, which may play a role in CFS and have close physiological connections with each other, from a pathophysiological perspective. In light of this evaluation, it aims to obtain data that will pave the way for the development and standartization of CFS diagnostic criteria. Material and Methods: For this purpose, the Chalder Fatigue Scale and the Fatigue Severity Scale were applied to initially evaluate whether the volunteers had CFS and to form the groups. Based on anamnesis, physical examination, and questionnaire results, CFS and control groups, each consisting of 30 volunteers, were formed. Both groups were administered the Physical Activity Questionnaire, Food Consumption Record, McGill Melzack Pain Questionnaire, Pittsburgh Sleep Quality Index (PSQI), Beck Depression Inventory, General Health Status Questionnaire, and Healthy Lifestyle Questionnaire.To evaluate the exercise capacities of the volunteers, cardiopulmonary exercise testing (CPET), muscle strength, balance, and jump tests were conducted. To assess the autonomic nervous system, heart rate variability (HRV), body temperature, respiratory rate, and galvanic skin response were measured along with body composition analysis, limb circumference measurements, venous blood gas analysis, and serum adropin levels. The data were analyzed using IBM Statistical Package for the Social Sciences (SPSS) for Windows version 25.0. Findings: Chalder fatigue scale, fatigue severity scale, pain questionnaire, PSQI, and Beck Depression Inventory results were significantly higher in the CFS group, while healthy lifestyle behaviors scale and SF-36 values were significantly lower in the CFS group. The balance test (p=0.01) and mean HR in HRV measurements (p=0.011) were lower, while mean RR (p=0.021) was higher in the CFS group. According to CPET results, FETO2 was significantly lower (p=0.029) and FETCO2 was significantly higher (p=0.040) in the CFS group. The percentage of CFS participants who could not complete the test due to fatigue and similar reasons was 56.7%. Spirometry results showed that FEV1, FEV1/FVC, and PEF values were significantly lower in the CFS group, while there was no significant difference in GDT, muscle strength, jump test, respiratory rate, and adropin levels. In blood gas analysis, lactate (p=0.009) and calcium (p=0.025) levels were found to be lower in the CFS group compared to the control group. Conclusion: In the diagnosis and monitoring of CFS, using the Chalder Fatigue Scale and the Fatigue Severity Scale alongside the Healthy Lifestyle Questionnaire, Beck Depression Inventory, Pittsburgh Sleep Quality Index, McGill Pain Questionnaire, and SF-36 could be beneficial. It is believed that the use of CPET and muscle strength testing (SFT) could also be advantageous in the diagnosis and monitoring of CFS. Developing a specific CPET protocol for CFS diagnosis could make CPET a gold standart method for diagnosis and monitoring. Venous blood lactate and calcium levels could be important biochemical markers in the diagnosis and monitoring of CFS. More research is needed to elucidate the detailed mechanisms.