ABSTRACT
Background:
Fibromyalgia syndrome (FMS) is a commonly occurring and disabling chronic pain disorder of unknown etiology. It is a syndrome of widespread diffuse pain with a low pain threshold and different FMS allied symptoms. Obesity is a comorbidity that is commonly occurring with FMS and may be linked to its severity. This study aims to estimate the prevalence of overweight and obesity in FMS and their effect on pain and FMS allied symptoms.
Methods:
One hundred and ten (10 male and 100 female) FMS patients diagnosed following the 1990 American College of Rheumatology (ACR) classification criteria for FMS completed a questionnaire about age, gender, and pain severity on a visual analog scale (VAS), evaluated for morning stiffness, disturbance of sleep, fatigue, anxiety, depression, and irritable bowel and the count of tender points. Weight, height, and body mass index (BMI) were calculated for all participants.
Results:
Seventy-four (67.27%) were overweight/obese; of them, 68 (61.81%) were females. All the FMS allied symptoms were more prevalent in overweight/obese FMS patients. Overweight/obese FMS patients have a high number of TP and greater pain sensitivity to TP palpation.
Conclusion:
Overweight and obesity are commonly associated with FMS. Obesity may contribute to the severity of FMS and its allied symptoms.
Keywords: Fibromyalgia, obesity, overweight, pain
Introduction
Fibromyalgia (FMS) is a worldwide chronic musculoskeletal disorder of uncertain etiology. It is a chronic, generalized widespread pain. Pain that lasts for at least three months is the characteristic of FMS and is associated with hyperalgesia to palpation on at least 11 out of 18 specific tender points (TPs), according to the 1990 American College of Rheumatology (ACR) criteria for the classification of fibromyalgia.[1] Patients with this disorder usually experience other complaints, such as morning stiffness, headache, fatigue, non-restorative sleep, cognitive disturbances (memory problems), irritable bowel, paresthesias, depression as well as anxiety.[2,3] FMS estimated prevalence is around 2% of the general population; it is more prevalent in women than in men. The etiopathogenetic mechanism of pain in FMS is still obscure and unknown.[4] Several factors such as malfunction of the central and autonomic nervous systems with reduced hypothalamic–pituitary–adrenal axis (HPA) activity,[5] abnormal endogenous pain modulation,[6] hormones neurotransmitters, immune system abnormalities,[7] external stressors, and psychiatric aspects have been proposed as contributing factors in the etiopathogenetic mechanism of FMS.[8] Obesity is a widely occurring disorder of excess accumulation of fat in the adipose tissue. The literature shows that musculoskeletal complaints and poor physical function are more prevalent in obese than normal-weight people.[9,10] Obesity is associated with different rheumatological and musculoskeletal disorders. The most significant association is between obesity with degenerative knee changes and low-back pain.[11,12] Researchers reported a connection between obesity and osteoarthritis of non-weight-bearing joints, such as hand joints.[13] Also, there is an apparent association between Carpal tunnel syndrome with obesity.[14] Studies declared that obesity is an essential disorder associated with FMS. Studies report that 32%–50% of FMS patients are obese, and an additional 21–28% are overweight.[15,16,17] Studies confirmed that patients who complain of FMS show high indexes of their body mass than non-FMS individuals.[18] The fact that; As BMI increases, pain/tender sensitivity proportionally increase, poorer quality of life, and low physical function in FMS.[15,16,17] Sensitivity to nociceptive stimuli is more remarkable in obese individuals.[19,20] Obese individuals typically show HPA axis abnormalities.[21,22] Obesity is also correlated with the level of proinflammatory mediators, such as C-reactive protein (CRP) and Interleukin-6 (IL-6).[23,24] Hence, obesity decreases the pain threshold that aggravates the widespread and diffuse pain in these patients; therefore, weight reduction measures may ease pain in FMS. We conducted this study to estimate the effect of overweight/obesity on patients with FMS and add support to this fact.
Patients and Methods
One hundred and ten (10 male and 100 female) FMS patients diagnosed in accordance with the 1990 American College of Rheumatology (ACR) classification criteria of FMS[25] were enrolled for this cross-sectional study. The study was carried out at the Rheumatology department and Rheumatology outpatient in Basra Teaching Hospital from March 2020 till April 2021. Patients who presented with another concomitant rheumatic disease that could justify the presence of chronic generalized pain were excluded from the study. In addition, participants with chronic health disorders such as uncontrolled diabetes mellitus and heart or renal failure, thyroid disorders, psychiatric disorders, rheumatologic, and cancer history were also excluded from the study. The patients answered a questionnaire that included age, sex, duration of FMS and its allied clinical symptoms, and drug history.
Evaluation and rating of pain
The widespread diffuse pain was evaluated using the visual analog scale (VAS), ranging from 0–10. The scale was anchored on the left with (no pain) and on the right with (the most intense pain), respectively.[26]
Tender point testing
It included the assessment of 18 tender points and 4 control non-tender points through digital palpation with an approximate force of 4 kg (the amount of pressure required to blanch a nail). The four control non-tender points are the middle of the forehead, the volar aspect of the mid-forearm, the thumbnail, and the anterior thigh muscles.[1]
Evaluation of FMS allied symptoms
All participants were asked about the following FMS-associated clinical features: morning stiffness, sleep disturbance, fatigue, headache, anxiety, depression, and irritable bowel. In addition, the Hospital Anxiety and Depression Scale (HADS)[27] was used for the evaluation of anxiety and depression.
Ethical considerations
All participants were given their written consent before their involvement for the study. The study was conducted in accordance with the principles of the Declaration of Helsinki.
Statistical analysis
SPSS software version 25.0 was used for data analysis. Percentages and mean were used to present the data in tables. Comparison of study groups was carried out using Chi-square and Fisher’s exact test for categorical data and Student’s t test for continuous data. A P value of < 0.05 was considered statistically significant.
Results
Seventy-four (67.27%) patients were overweight/obese, and 36 (32.73%) were normal weight; the difference was statistically significant (p < 0.05); 68 (61.81%) were overweight/obese females, and 32 (29.09%) were normal-weight; the difference was statistically significant (p < 0.05). Mean age and disease duration of overweight/obese and normal-weight patients were 41 ± 2.1, 9 ± 2.3, 40 ± 6.1, and 9 ± 3.4, respectively. The mean BMI of overweight/obese and normal-weight patients was 35 ± 3.3 and 19 ± 3.1, respectively; the difference was statistically significant (p < 0.05), as shown in Table 1. Morning stiffness, sleep disturbance, headache, fatigue, anxiety, and depression in overweight/obese FMS patients were 87.8%, 86.5%, 86.5%, 89.2%, 85.13%, and 86.5%, respectively; percentages were all higher than those of normal-weight FMS patients, and the difference was statistically significant (p < 0.05 for all). While irritable bowel was found in 56.7% and 44.5% of overweight/obese FMS patients and normal-weight FMS patients, the difference was statistically insignificant (>0.05), as shown in Table 2. The mean tender points count (TPC) and mean and VAS for overweight/obese were higher than those for normal-weight FMS patients; the difference was statistically significant (p < 0.05 for both), as shown in Table 2.
Table 1.
Demographic and clinical data of FMS patients
| Characteristic | FMS with overweight/obesity | Normal-weight FMS | P |
|---|---|---|---|
| Total n 110 (100%) | 74 (67.27%) | 36 (32.73%) | <0.05 |
| Male 10 (9.1%) | 6 (5.47%) | 4 (3.63%) | >0.05 |
| Female 100 (90.9%) | 68 (61.81%) | 32 (29.09%) | <0.05 |
| Mean age±SD (years) | 41±2.1 | 40±6.1 | >0.05 |
| Mean disease duration±SD (years) | 9±2.3 | 9±3.4 | >0.05 |
| Mean BMI±SD | 35±3.3 | 20±3.1 | <0.05 |
BMI=Body Mass Index
Table 2.
Differences in FMS allied symptoms, number of tender points, and VAS in overweight/obesity and normal-weight patients
| Parameter | FMS with overweight/obesity | Normal-weight FMS | P |
|---|---|---|---|
| Total n 110 (100%) | 74 (100%) | 36 (100%) | <0.05 |
| Morning stiffness | 65 (87.8%) | 14 (38.8%) | <0.05 |
| Headache | 64 (86.5%) | 12 (33.33%) | <0.05 |
| Fatigue | 66 (89.2%) | 13 (36.11%) | <0.05 |
| Anxiety | 63 (85.13%) | 12 (33.33%) | <0.05 |
| Depression | 64 (86.5%) | 11 (30.5%) | <0.05 |
| Irritable bowel | 42 (56.7%) | 16 (44.5%) | >0.05 |
| Mean TPC±SD | 17±1.8 | 11±1.3 | <0.05 |
| Mean VAS±SD | 8±4.6 | 4±2.1 | <0.05 |
TPC=Tender Point Count, VAS=Visual Analog Scale
Discussion
FMS patients commonly have a high percentage of overweight and obesity. Several independent study groups showed that obesity is prevalent in patients with FMS at about 40% and overweight at about 30%.[16,28] Another report estimated a prevalence of 34.1% for overweight and 32.2% for obesity.[29] Obesity is an aggravating comorbid condition that negatively affects the severity of FMS, global quality of life, physical dysfunction, and fatigue. Obese individuals have an expanding risk of developing FMS, especially those physically inactive.[30] In agreement with the above findings, obesity/overweight was prevalent in this study, with a percentage of 67.27%. Similar findings were reported by Neumann et al., Okifuji et al., Kim et al., Aparicio et al., and Cordero et al.[15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34] In a study on 2569 FMS patients, 70% of FMS patients had a BMI of 25 kg/m2, and 43% had a BMI of 30 kg/m2.[28] Different mechanisms were proposed to explain “the hidden link” between both disorders FM and obesity, but whether obesity is a cause or a consequence of FM is difficult to ascertain. Among the proposed mechanisms are sleep disturbances, depression, reduced physical activity, dysfunction of the GH/IGF-1 axis, and dysfunction of the thyroid gland. Obesity alters the sensitivity to noxious stimuli via obesity-related dysregulation in the endocrine and opioid systems. Okifuji et al.[16] reported that obesity in FM is related to greater levels of proinflammatory indices involved in central sensitization and to the development of chronic latent hyperalgesia in muscles. The most plausible explanation is that all these factors contribute to determining the obese phenotype of many patients and that obesity contributes to perpetuating and worsening the severity of FM.[35] Another simple explanation for this high prevalence could be reduced physical activity. In fact, FMS is a crucial cause of disability,[36] thus reducing physical activity. However, this explanation is very simple when we consider other explanations published in the literature. Disturbed sleep is a key clinical characteristic of FMS that is associated with obesity.[37] Obesity has been demonstrated to induce bad sleep quality and shorter duration.[38,39] Although pain sensitivity seems to be reduced and pain threshold higher in obese patients,[40,41] obesity could influence the severity of fibromyalgia via worsened sleep. Obesity could influence the severity of fibromyalgia via worsened sleep. Another possible mechanism to explain the link between obesity and fibromyalgia is psychological disturbances associated with FMS. Fibromyalgia is closely related to depression,[3] which appears to influence body weight resulting in weight disturbances like obesity.[42] FMS-associated clinical symptoms were more prevalent in overweight/obese patients compared to normal weight in our study population. Sleep disturbance has been postulated as a potential link between obesity and FMS.[43] In fact, FMS is implicated in bad sleep quality, and overweight and obesity are involved with sleepiness in these patients.[31,44] Additionally, sleep problems have been reported to play a critical role in exacerbating FMS symptoms since sleep may predict subsequent pain in FMS patients.[45] In contrast to the finding reported by Yunus et al.[17] and, Zahorska-Markiewicz et al.,[41] who did not observe any significant link between overweight/obesity and anxiety, fatigue, and TPC in obese groups as compared with a normal weight group, we reported a significant association. In accordance with the previous findings,[31] obesity was related to increased TP pain sensitivity assessed by VAS. The cross-sectional nature and the lack of casual relationships are the limitations of our study.
Conclusion
Obesity is commonly associated with FMS as significant comorbidity. Obesity significantly contributes to the severity of FMS and its allied symptoms. Obesity is also associated with a higher number of tender points and higher pain sensitivity.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Acknowledgement
We kindly appreciate the role of all participants in the study.
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