Introduction

Fibromyalgia syndrome (FMS) is a chronic rheumatic condition characterized by numerous symptoms, including tenderness in specific areas of the body, reduced pain threshold, fatigue, psychological issues, and sleep disturbances¹. FMS affects approximately 2% of the general population, predominantly middle-aged women². In a study conducted with 1930 females in Türkiye, the prevalence of fibromyalgia was found to be 3.6%³. Patients were diagnosed with FMS based on the 2016 diagnostic criteria established by the American College of Rheumatology (ACR)⁴. The etiology and pathogenesis of FMS are not fully known. Furthermore, genetic disorders, and causal factors such as the occurrence of trauma, the inflammation process, mental stress, and infections may change the neuroendocrine mechanisms related to pain or can trigger deterioration⁵.

Sarcopenia is characterized as a progressive and generalized musculoskeletal disorder involving accelerated muscle mass decline and functional impairment⁶. It is a relatively uncommon condition in the musculoskeletal spectrum. The European Working Group on Sarcopenia in Older People (EWGSOP)⁶ established a consensus definition and clinical diagnostic criteria for sarcopenia in 2010, later updated as EWGSOP2 in January 2019⁷. There is limited research exploring the association between fibromyalgia and sarcopenia. Within the International Society of Physical and Rehabilitation Medicine (ISPRM) framework, Kara et al.⁸ determine the diagnostic algorithm for sarcopenia (ISarcoPRM). And also Kara et al.⁹ used the ultrasonographic evaluation to clarify the diagnoses of sarcopenia.

Because of widespread body pain, physical activity level decreases in FMS. A small number of studies in the literature have examined the relationship between fibromyalgia and sarcopenia¹⁰,¹¹. Our study aims to explore the prevalence of sarcopenia in fibromyalgia patients using the new ISarcoPRM criteria and to investigate potential correlations between physical performance, disease activity, pain levels, and sarcopenia presence.

Method

This cross-sectional study was conducted in the Turkish population and included 50 female patients diagnosed with FMS based on the 2016 ACR criteria, along with 50 healthy controls matched for age and sex. The participants were recruited from the Physical Medicine and Rehabilitation outpatient clinic for routine health check-ups, including physical examinations and hemogram measurements, between August 2023 and December 2023. The study received ethical approval from the Local Ethics Committee of the University (decision number 114, 2023) and adhered to the principles of the Declaration of Helsinki. All participants provided informed consent before enrollment, and they were thoroughly briefed about the study protocol.

Female subjects between 25-65 years old, diagnosed with fibromyalgia for at least 6 months were included in the study. Patients undergoing physical therapy in the past 3 months, had a history of concomitant rheumatic disease, diabetes mellitus, hypertension, myopathies, diseases that affect ambulation such as lower extremity operations, peripheral or central nervous system disease, severe lung or heart failure, kidney or liver diseases, malignancy, pregnancy or breastfeeding or any psychiatric disorder, and any medications that could influence muscle function, such as steroids were excluded from the study. After the demographic characteristics of the patients were recorded, physical examinations were performed and body mass indexes (BMI) were noted. All evaluations were made by the same physician.

The Fibromyalgia Impact Questionnaire (FIQ) was used to evaluate the disease activity and it comprises ten items organized into three domains: functional, physical symptoms, and mental symptoms. Each item is rated on a scale (0-10), where lower scores indicate better disease activity. Sarmer et al.¹² established the reliability of the FIQ in the Turkish population.

The numerical rating scale (NRS)¹³ was employed to evaluate pain levels, where patients rated their pain on a scale from 0 to 10, high scores describe more severe pain.

Sarcopenia was screened by the SARC-F questionnaire¹⁴. It includes five questions, each question scores 0-2 points. Five domains are rising from chair strength, stair climbing, walking ability, and history of falls. A score of 4 points or higher is indicative of sarcopenia.

The presence of sarcopenia was evaluated according to ISarcoPRM⁸. According to ISarcoPRM diagnostic algorithm for sarcopenia, the first hand grip strength was measured with a Jamar dynamo meter in kilograms (Saehan hydraulic hand dynamometer)¹⁵. Patients performed the test 3 times with each hand, with 30 s rest between trials then an average of three trials calculated separately for the right and left hands. Results under 19 kg were assessed as probable sarcopenia. Then, anterior thigh muscle thicknesses were evaluated with ultrasonography. Ultrasound was used to measure the anterior thigh muscle thickness on the quadriceps femoris. All measurements were conducted by the same researcher. A multi-frequency probe (6-12 MHz: Philips purewave) was utilized for ultrasound examinations. Participants were positioned supine with legs extended and muscles relaxed, and images were captured midway between the superior border of the patella and the anterior superior iliac spine. Sonographic Thigh Adjustment Ratio (STAR) is already suggested for the diagnosis of sarcopenia⁸. If the ratio was under 1.0 in females, this was accepted as sarcopenia. The presence of sarcopenia was recorded.

Physical performance was assessed with the test of five times sit-to-stand test (FTSST) and usual gait speed with 6 meters walk test (6MWT). At FTSST subjects sit down without touching the back of the chair and stand up fully for 5 times and time was measured in seconds¹⁶. The 6MWT, a 6-m flat path, was marked on the hospital corridor, participants walked on the path and walking time was measured in seconds¹⁷. Above 15 s was accepted as a disability according to the ISarcoPRM diagnostic algorithm⁸.

Results

Age, weight, height, and BMI were similar in FMS patients and the control group (Table 1). SARF-C score, 6MWT, and FTSST tests were significantly higher in patients with FMS (p < 0.001). The presence of sarcopenia was found as 20 (40%) in FMS patients and 6 (12%) in healthy controls according to ISarcoPRM criteria (p < 0.001). Right-hand grip strength was significantly different in patients with FMS (p = 0.007). Right anterior thigh muscle thickness is similar in the two groups (p = 0.875). FTSST and 6MWT were significantly decreased in FMS patients (p < 0.001).

NRS and FIQ scores were not different between FMS patients with sarcopenia and FMS patients without sarcopenia (Table 2). A positive correlation was found between FIQ score and SARF-C score in FMS patients with sarcopenia (r = 0.708, p < 0.001). However, FIQ score was not correlated with anterior thigh muscle thickness, hand grip strength, 6MWT, and FTSST tests (Table 3).

Discussion

This study revealed an elevated prevalence of sarcopenia among patients with FMS. Although there is no difference in anterior thigh muscle thickness measured by USG, we evaluated a loss in physical performance and hand grip muscle strength in patients with FMS. We identified a correlation between the severity of fibromyalgia symptoms and the presence of sarcopenia.

There are a few studies investigating the frequency of sarcopenia in FMS¹¹,¹². An important point about our study was that we used the US for diagnosing sarcopenia. Dual X-ray absorptiometry (DXA), magnetic resonance imaging (MRI), computerized tomography (CT), ultrasonography (US), and bio-electrical impedance analysis (BIA) can be used for evaluating muscle mass. In addition to the radiation to which the patient is exposed, specific muscle mass cannot be evaluated by DXA. CT and MRI are the gold standard methods for quantifying muscle mass but they are expensive and time-consuming procedures. The US is portable, easier, and cheaper. Because of that, we used the US for evaluating the muscle mass in our study according to ISarcoPRM criteria.

In a previous study¹⁸, quadriceps femoris muscle mass, evaluated by ultrasonography, was found to be significantly lower in FMS patients. However, this study did not investigate the relationship between muscle mass, muscle strength, and physical performance. In a larger study¹⁹, muscle mass was assessed using BIA, revealing no differences between FMS patients and healthy controls. Our study found similar anterior thigh muscle mass thickness between FMS patients and healthy participants. Despite no observed loss of muscle mass, our research identified reduced muscle strength in patients with FMS. Unlike these two studies, we utilized ultrasound for evaluation, employing a more detailed methodology.

Some studies showed that muscle strength and physical performance reductions were found in FMS patients similar to our study⁶,²⁰,²¹. These studies also showed a relationship between disease activity and quadriceps femoris muscle strength²¹-²³. We found decreased hand grip strength in patients with FMS. However, we did not evaluate the quadriceps femoris muscle strength and we did not find a relationship between hand grip strength and disease activity in our study.

We did not classify patients according to the duration of fibromyalgia diagnosis or age range. Muscle strength may decrease more over time in patients with long-term disease¹⁰. At the same time, if patients were classified according to their age range, different results related to muscle strength may be obtained. In the previous study, patients with FMS were examined at 10-year age intervals and hand strength decreased significantly every 10 years, although muscle mass remained the same¹⁹. Devrimsel et al.²³ found higher hand disability scores in patients with FMS than in healthy populations. This shows that the assessment of hand strength is not only useful for screening sarcopenia but also may help to prevent disability. According to the results of our study, it is useful to be vigilant for sarcopenia in FMS patients with low hand grip muscle tests.

The previous study conducted in patients who developed sarcopenia after COVID-19 infection showed that high-intensity exercise increases hand grip strength, physical performance, and quality of life compared to low-intensity exercise²⁴. Likewise, in the previous studies, we also found a significant loss in physical performance in FMS patients compared to healthy controls⁶,²⁰,²¹. It is debatable whether fibromyalgia itself reduces physical performance or whether physical activity and, therefore, poor performance trigger fibromyalgia. In conclusion, the increased prevalence of sarcopenia and poor physical performance which we found in fibromyalgia patients may be due to lack of physical activity. In this case, an increased frequency of sarcopenia in fibromyalgia patients seems to be an expected result. This study once again emphasizes the importance of exercise and strategies to prevent sarcopenia and improve the quality of life in patients with fibromyalgia. Another study conducted in elderly adults found that patients with sarcopenia had higher mortality during in-hospital follow-up²⁵. A meta-analysis involving women with ovarian cancer showed that sarcopenia and low muscle mass were associated with poor survival and high mortality²⁶. This suggests that sarcopenia is not only associated with quality of life but also with mortality in later life. For this reason, it is important to be diagnosed and treated at a young age.

Some studies were found that patients with FMS had significantly decreased muscle strength, functional performance, and exercise capacity compared with healthy individuals²⁷-²⁹. Also in some studies, the values of the fat mass percentage were found higher in FMS patients³⁰. In FMS, insulin-like growth factor I levels decrease, and proinflammatory cytokines IL-1beta, and TNF-a are increased³¹. These cytokines are also thought that they be associated with the development of sarcopenia³²; on all these facts, there may be a connection between sarcopenia and FMS.

Chronic muscle pain has a great impact on the performance of daily activities. Being aware that the pain occurs with isokinetic movements has been reported among the possible causes of poor muscle performance in patients with FMS²⁸,²⁹. In our study, there was no relationship between sarcopenia and pain level in patients with FMS. This may suggest that there are more different factors than pain that play a role in muscle mass and strength in fibromyalgia.

FMS occurs in young women of reproductive age. In patients who develop sarcopenia at this age, not only functionality is affected but it alos can cause serious morbidity in patients at older ages. Sarcopenia in the elderly is an expected outcome, but affecting women of this age may also cause socioeconomic problems. So far, no complete protocol has been applied in previous studies on sarcopenia in patients with FMS. In a study, sarcopenia was assessed only by muscle strength, in the other only by the US or by functional status. In our study, we used both the SARC-F questionnaire, upper and lower extremity performance, and at the end US as an objective assessment parameter. This was a valuable study because there are a few studies about FMS and sarcopenia in the literature and sarcopenia is common in young women with FMS. However, there are some limitations in our study. Only female FMS patients were invited to our study and we did not comment on male FMS patients. Second, we did not know the other conditions that can affect sarcopenia such as physical activity levels, and nutritional status.

Conclusion

As a result of this study, we think that sarcopenia is common in patients with FMS. Hand strength is useful for suspecting sarcopenia. Assessing the presence of sarcopenia in FMS patients may improve the success of FMS treatment by improving the exercise program.