Comment on: Johns and Littlejohn, The role of sex hormones in pain response

Chronic Fatigue Syndrome and Chronic Widespread Pain in Adolescence: Population Birth Cohort Study

Although many studies have investigated the overlap between pain phenotypes and chronic fatigue syndrome (CFS) in adults, little is known about the relationship between these conditions in adolescents. The study's aim was therefore to identify whether a relationship exists between chronic widespread pain (CWP) and CFS in adolescents and investigate whether the two share common associations with a set of covariates. A questionnaire was administered to offspring of the Avon Longitudinal Study of Parents and Children (ALSPAC) at age 17, asking about site, duration, and pain intensity, from which participants with CWP were identified. At the same research clinic, a computer-based Revised Clinical Interview Schedule was filled out, from which a classification of CFS was obtained. The relationship between selected covariates and CFS and CWP was investigated using a variety of logistic, ordinal logistic, and multinomial regressions. We identified 3,214 adolescents with complete data for all outcomes and covariates. There were 82 (2.6%) individuals classified as CFS and 145 (4.5%) as CWP. A classification of CFS resulted in an increased likelihood of having CWP (odds ratio = 3.87; 95% confidence interval, 2.05-7.31). Female adolescents were approximately twice as likely to have CFS or CWP, with multinomial regression revealing a greater sex effect for CWP compared with CFS. Those with exclusive CFS were more likely to report higher levels of pain and greater effect of pain compared with those without CFS, although associations attenuated to the null after adjustment for covariates, which did not occur in those with exclusive CWP. Multinomial regression revealed that relative to having neither CFS nor CWP, a 1-unit increase in the depression and anxiety scales increased the risk of having exclusive CFS and, to a greater extent, the risk of having comorbid CFS and CWP, but not exclusive CWP, which was only related to anxiety.

PERSPECTIVE

In this cohort, 14.6% of adolescents with CFS have comorbid CWP. The likely greater proportion of more mild cases observed in this epidemiological study means that prevalence of overlap may be underestimated compared with those attending specialist services. Clinicians should be aware of the overlap between the 2 conditions and carefully consider treatment options offered.

Prevalence of chronic widespread pain and fibromyalgia syndrome: a Korean hospital-based study

This study was conducted to estimate the point prevalence of chronic widespread pain (CWP) and fibromyalgia syndrome (FMS) in a primary care center of a hospital in Korea. CWP was defined as pain lasting more than 3 months involving all the classified pain sites (axial, left and right, above and below waist). FMS was diagnosed by the American College of Rheumatology (ACR) criteria and also by clinical judgment of a physician. All 1,077 subjects were classified into three groups as no chronic pain (NCP), chronic regional pain (CRP), and CWP. CRP was defined as chronic pain with the exception of CWP. The point prevalence of CWP was 6.5% (95% confidence interval (CI) 0.2-12.8) and the point prevalence of FMS was 1.7% (95% CI 0.0-4.9) by ACR criteria and 2.3% (95% CI 0.0-6.1) by clinical judgment, respectively. We also analyzed the differential demographic characteristics among patients with NCP, CRP, and CWP. When compared to NCP, CWP was significantly associated with the female gender after adjusting for other variables (odds ratio 4.2; 95% CI 1.4-12.4, P = 0.009). Compared to NCP, CWP patients had lower levels of education (P = 0.018), a lower likelihood of a professional occupation (P = 0.014), infrequent alcohol intake (P = 0.014) and a lower proportion of current smokers (P = 0.003) based on a univariable analysis. In this Korean hospital-based study, CWP patients were common and had different demographic characteristics and life habits from NCP.

Epidemiology of chronic musculoskeletal pain

The rate of musculoskeletal pain in adolescent and adult populations is examined, with a focus on three commonly reported pain disorders: shoulder pain, low back pain and fibromyalgia/chronic widespread pain. There is a paucity of data on musculoskeletal pain in adolescent populations. Those studies available suggest that pain is common, although the actual rates are unclear. This is probably due to differences in study methodologies and populations. Pain is commonly reported among adult populations, with almost one fifth reporting widespread pain, one third shoulder pain, and up to one half reporting low back pain in a 1-month period. The prevalence of pain varies within specific population subgroups; group factors (including socioeconomic status, ethnicity and race) and individual factors (smoking, diet, and psychological status) are all associated with the reporting of musculoskeletal pain. However, the precise nature of these relationships, and particularly the mechanisms of association, are unclear and require further investigation.

Specificity of female and male sex hormones on excitatory and inhibitory phases of formalin-induced nociceptive responses

Several factors have been proposed to account for the differences observed between men and women in pain perception. One of these is female and male gonadal hormones. In order to verify this assumption, a hormone replacement (pellets inserted subcutaneously) of (1) 17beta-estradiol, (2) progesterone, (3) 17beta-estradiol + progesterone or (4) testosterone have been performed in gonadectomized female and male Sprague-Dawley rats. Twenty-one days after the hormonal replacement, a formalin test was performed. The nociceptive responses were divided in three distinct phases: acute (phase I), inhibitory (interphase) and tonic (phase II). After analysis, we observed that testosterone has a hypoalgesic effect on phases I and II of the formalin test. At the opposite, female hormones act only on the interphase: the combination of 17beta-estradiol and progesterone in gonadectomized rats reestablishes the weaker nociceptive pain reduction during the interphase as it is observed in the intact female. These effects were not gender specific since they had the same action in female and male. Our results permit to believe that testosterone plays a protective role in pain perception. Moreover, the female hormones act mainly on pain inhibition mechanisms (interphase), suggesting that the prevalence of certain chronic pain conditions in women could be related to a deficit of these pain inhibitory mechanisms rather than an increased nociceptive activity.

Menstrual cycle influences on pain and emotion in women with fibromyalgia

OBJECTIVE

This study examined the influence of the menstrual cycle on pain and emotion in women with fibromyalgia (FM) as compared with women with rheumatoid arthritis (RA) and to healthy controls.

METHODS

One hundred and twenty-five premenopausal women (21-45 years old) participated in this study (57 with FM, 20 with RA, and 48 controls). Pain and emotion assessments were conducted during the follicular and the luteal phases of the menstrual cycle.

RESULTS

Women with FM experienced more pain, menstrual symptoms, and negative affect than did women with RA and the controls. All women reported less positive affect during the luteal phase, although this pattern was more pronounced in women with FM and RA than in controls.

CONCLUSION

Although FM pain did not vary across the menstrual cycle, these results point to the importance of considering the lower level and cyclical nature of positive affect when studying women with chronic pain.

Fibromyalgia: a stress disorder? Piecing the biopsychosocial puzzle together

Fibromyalgia (FM) is a controversial syndrome, characterised by persistent widespread pain, abnormal pain sensitivity and additional symptoms such as fatigue and sleep disturbance. The syndrome largely overlaps with other functional somatic disorders, particularly chronic fatigue syndrome (CFS). Although the exact aetiology and pathogenesis of FM are still unknown, it has been suggested that stress may play a key role in the syndrome. This article first reviews the function of the stress response system, placing special emphasis on the relationships between adverse life experiences, stress regulation and pain-processing mechanisms, and summarising the evidence for a possible aetiopathogenetic role of stress in FM. Finally, an integrative biopsychosocial model that conceptualizes FM as a stress disorder is proposed, and the clinical and research implications of the model are discussed.

Psychological stress and fibromyalgia: a review of the evidence suggesting a neuroendocrine link

The present review attempts to reconcile the dichotomy that exists in the literature in relation to fibromyalgia, in that it is considered either a somatic response to psychological stress or a distinct organically based syndrome. Specifically, the hypothesis explored is that the link between chronic stress and the subsequent development of fibromyalgia can be explained by one or more abnormalities in neuroendocrine function. There are several such abnormalities recognised that both occur as a result of chronic stress and are observed in fibromyalgia. Whether such abnormalities have an aetiologic role remains uncertain but should be testable by well-designed prospective studies.

Evaluation and management of endocrine dysfunction in fibromyalgia

Fibromyalgia-like symptoms such as muscle pain and tenderness, exhaustion, reduced exercise capacity, and cold intolerance, resemble symptoms associated with endocrine dysfunction like hypothyroidism, and adrenal or growth hormone insufficiency. To investigate the potential of management of endocrine abnormalities for relieve of symptoms of patients with fibromyalgia, we reviewed experimental and clinical studies of endocrine functioning and endocrine treatment. Serum GH, androgen, and 24-hour urinary cortisol levels of patients with fibromyalgia tend to be in the lower part of the normal range, while serum levels of thyroid hormone, female sex hormones, prolactin, and melatonin are normal. With exception of GH, these conclusions are based on studies in small samples. With respect to dynamic responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis, the dexamethasone suppression test and stimulation with ACTH show normal results, while patients show marked ACTH hypersecretion in response to severe acute stressors, perhaps indicative of chronic CRH hyposecretion. This finding and slightly altered responsiveness of growth hormone, thyroid hormone, and prolactin in pharmacologic stimulation tests suggest a central rather than peripheral origin of endocrine deviations. Because hormone level deviations were not severe, occurred in subgroups of patients only, and few controlled clinical trials were performed, there is--unless future research shows otherwise--little support for hormone supplementation as a general therapy in the common patient with fibromyalgia. In patients with clinically overt hormone deficiency, hormonal supplementation is an option. In patients with hormone levels that are in the lower part of the normal range, interventions aimed at pain, fatigue, sleep or mood disturbance, and physical deconditioning may indirectly improve endocrine functioning.