Table 1.

Selected studies with their main findings.

Reference (Country) Study Type	Aim	Sample	Questionnaires and Scales	Findings
Segura-Jiménez et al., 2016 (Spain) [24] Comparative Cross-Sectional Study Quantitative	To examine gender differences in sensitivity, fibromyalgia impact, health-related quality of life, fatigue, sleep quality, mental health, cognitive performance, pain cognition and positive health in Spanish fibromyalgia patients and non-fibromyalgia individuals of the same age and region. To observe the optimal cut-off score of the different sensitive items for women and men.	FM patients = 388 W = 367 M = 21 No FM patients = 285 W = 232 M = 53	Tender Points (0–18)	FM-W: 16.8 ± 0.1 FM-M: 16.8 ± 0.4 p = 0.877 NS No FM-W: 3.3 ± 0.2 No FM-M: 0.8 ± 0.4 p < 0.001 Women reported greater pain sensitivity
			Fibromyalgia Impact Questionnaire (0–100)	FM-W: 64.7 ± 0.9 FM-M: 65.5 ± 3.6 p = 0.837 NS No FM-W:20.7 ± 0.9 No FM-M:18.7 ± 1.9 p = 0.339 NS
			Pain Catastrophizing Scale (0–52)	FM-W: 25.1 ± 0.7 FM-M: 26.2 ± 2.7 p = 0.712 NS No FM-W: 11.2 ± 0.7 No FM-M: 9.9 ± 1.5 p = 0.427 NS
Wolfe et al., 2018 (EE. UU.) [25] Longitudinal Study Quantitative	To compare CritFM with ClinFM to investigate gender and other biases in fibromyalgia diagnosis.	FM patients = 4342 W = 2171 M = 2171 Age = 56.6 ± 12.6 years W = 59.7 ± 13.5 years M = 64.9 ± 12.0 years	Widespread Pain Index (0–19)	FM-W:5.9 ± 0.7 FM-M:4.9 ± 1.3
			Symptom Severity Scale (0–12)	FM-W = 4.3 ± 0.7 FM-M = 3.4 ± 1.1
			Polysymptomatic Distress (0–31)	FM-W = 10.2 ± 1.6 FM-M = 8.2 ± 1.6
			Pain Visual Analogue Scale (0–10)	FM-W = 3.9 ± 0.3 FM-M = 3.4 ± 1.0
			Higher values of pain and symptom severity were detected in women relative to men. Since FMS is defined based on pain and symptom severity, women will always be more likely to be diagnosed. In short, there is a relationship between being female and being diagnosed with FMS.
Prateepavanich et al., 2018 (Thailand) [26] Cross-Sectional Study Quantitative	To obtain demographic data, clinical characteristics and investigate correlations of clinical features in Thai patients with FMS.	FM patients = 71 W = 69 M = 2 Age = 44.83 (±10.81) years	Pain Visual Analogue Scale (0–100)	63.39 ± 17.8
			Fibromyalgia Impact Questionnaire (0–100)	45.48 ± 16.83
De Roa et al., 2018 (France) [27] Comparative Cross-Sectional Study Quantitative	To characterize childhood experiences, perceived lack of parental affection, hypersensitivity to stimuli, life stressors, anxio-depression and ergomania.	FM-W patients = 44 Migraine-W patients= 34 Age = 45 ± 12 years	Pain Visual Analogue Scale (0–10)	Better moments: FM-W = 3.3 ± 1.9 Migraine-W= 1.8 ± 2.3 Worse moments: FM-W = 8.9 ± 1.4 Migraine-W= 8.7 ± 1.2 NS Scores
Jiao et al., 2021 (China) [1] Cross-Sectional Study Quantitative	To characterize the demographics, severity of fibromyalgia-related symptoms and quality of life (QoL) among Chinese fibromyalgia patients.	FM patients = 124 FM-W = 107 FM-M = 17 Age-W = 50.1 years Age-M = 43.6 years P = 0.027 M significantly younger Mean age= 49.4 years	Pain Visual Analogue Scale (0–100)	FM-W: 56.2 ± 21.7 FM-M: 54.1 ± 25.5 p = 0.72 NS
			Widespread Pain Index (0–19)	FM-W = 11.1 ± 4.7 FM-M = 8.6 ± 3.9 p = 0.038 Women higher values of pain
			Symptom Severity Scale (0–12)	FM-W = 7.4 ± 2.6 FM-M = 8.7 ± 1.8 p = 0.06 Males higher values of symptom severity
			Polysymptomatic Distress (0–31)	FM-W = 18.5 ± 5.9 FM-M = 17.2 ± 4.6 p = 0.40 NS No gender differences in either group
Úbeda-D’Ocasar et al., 2021 (Spain) [28] Descriptive Exploratory Study Quantitative	To assess the pain pressure thresholds (PPT) and subjective pain perception (SPP) of the 18 PTs while applying standardized pressure.	n= 30 W Mean age = 55.1 ± 8.7 years	Fibromyalgia Impact Questionnaire (0–100)	FM-W: 64.1 ± 14.4 Nine locations were examined bilaterally: TP1 forehead; TP2 intertransverse space of C5-C7; TP3 midpoint of the trapezius muscle; TP4 supraspinatus muscle; TP5 second costochondral junction; TP6 2 cm distal to the lateral epicondyle; TP7 upper outer quadrant buttocks; TP8 trochanteric prominence; TP9 in the medial fat of the knee.
			Pain Visual Analogue Scale (0–100)	The most painful points located in: TP7: 69.6 ± 19.4 TP8: 68.0 ± 21.5 TP4: 65.1 ± 21.1 The lowest points located in: TP5: 1.28 ± 0.42 TP1: 1.52 ± 0.34 TP8: 1.61 ± 0.59 p > 0.05 NS
Iannuccelli et al., 2022 (Italy) [29] Cross-Sectional Study Quantitative	To evaluate the influence of gender on clinical manifestations, with special attention to the neuropsychiatric features of FMS.	n = 172 W n = 29 M Mean age = 49.13 years	Pain Visual Analogue Scale (0–10)	FM-W = 7.5 ± 1.64 FM-M = 6.52 ± 2.06 p = 0.0130
			Fibromyalgia Impact Questionnaire (0–100)	FM-W = 68.07 ± 16.06 FM-M = 55.17 ± 18.26 p = 0.0005
			Widespread Pain Index (0–19)	FM-W = 10.67 ± 3.91 FM-M = 10.90 ± 4.81 p = NS No gender differences in either group
			Symptom Severity Scale (0–12)	FM-W = 9.24 ± 1.72 FM-M = 8.724 ± 1.79 p = NS No gender differences in either group
Kueny et al., 2021 (EEUU, Spain) [30] Mixed (1. Quantitative)	To describe the pain and fatigue experiences of men with MFS from Spain and the United States.	n = 17 M Spain-M = 10 USA-M = 7 Age range = 30–63 years Mean Age = 52 years	Fibromyalgia Impact Questionnaire (0–100)	Spain M: 81.93 ± 5.89 USA M: 67.99 ± 15.33 p = 0.08 The difference only approached statistical significance.
(2.  Qualitative )	To describe the pain and fatigue experiences of men with MFS from Spain and the United States.	n = 17 M Spain-M = 10 USA-M = 7 Age range = 30–63 years Mean Age = 52 years	Focus groups and interviews	Common experiences (Spanish and American) include fluctuating pain (especially with movement), pain considered invisible to others and localized pain. Pain triggers, such as thermosensitivity. Physical exertion, such as walking. Both samples acknowledged that the more they moved, the more pain they experienced.
Sallinen and Mengshoel, 2017 (Finland) [16] Qualitative	To elucidate the impacts of FMS on men’s daily life and work capacity.	n = 5 M	Life story	Major changes in their work, hobbies and diet to control symptoms, such as pain. Participants recognized the importance of physical activity and struggled to find an activity that did not aggravate aches and pains.
Sendra and Farré, 2020 (Global) [31] Qualitative	To identify how and why patients use online platforms for pain communication.	n = 350 M and W	Narrative	Sharing the painful experience can be beneficial for patients, because chronic pain brings constant problems and disbelief. Illness narratives allow patients to explain this condition in new ways. However, the lack of time in doctor–patient interactions hinders the use of this intervention for communication by increasing the communication gap. With the Internet era, patients have sought other venues to express their concerns in online settings. Patients often do not disclose their disease to avoid stigmatization and disbelief when interacting with others.

FM: Fibromyalgia, W: Women, M: Men, NS: Not significant.