A study conducted on data collected by the Korea National Institute of Health, South Korea, has allowed a ground-breaking analysis on fibromyalgia, confirming its association with optic neuritis, thus paving the way to further studies on the connections between fibromyalgia and similar pathologies
Professors Hyung Rae Cho, Geung Kyu Lee and Ju-Yeun Lee, from the Hanyang University College of Medicine, and doctors from the Myongji Hospital in Seoul, South Korea, pooled data from the Korean National Health Claims database from 2012 to 2021, to conduct a nationwide study that confirmed an increased incidence of optic neuritis in fibromyalgia patients.
Fibromyalgia is a chronic disease and it is more common than one might think. It is characterised by a combination of neurological and autonomic symptoms in the absence of peripheral musculoskeletal inflammation or structural damage. The main symptom of fibromyalgia is pain, followed by fatigue, depression, cognitive and sleep disorders, ataxia and various somatic symptoms.
According to the Italian Society of Rheumatology, there are as many as 2 million people suffering from fibromyalgia in Italy. However, fibromyalgia is not included in the Minister of Health’s list of chronic diseases, thus precluding patients from accessing essential levels of care.
Several hypotheses on the pathogenesis of fibromyalgia have been proposed, with the most recent focusing on the involvement of mechanisms associated with autoimmunity and neuroinflammation. The first hypothesis, in particular, is rooted in the connection between autoimmune diseases and negative events, such as infections and trauma, that may plausibly induce autoimmunity.
Regardless of such hypothesis, it has emerged that fibromyalgia is very often associated with various eye conditions. This association is easily explained by tissue and nerve inflammation that are triggered by an autoimmune activation of fibromyalgia.
Several researchers have also identified the presence of an extremely high number of autoantibodies in the gangliosides, which not only is relevant in the presence of autoimmunity, but, since the second-highest incidence of autoantibody density in the human body is found in the optic nerve, the latter is more vulnerable to conduction blocks.
Additionally, another recent clinical study recorded axonal damage to the optic nerve in fibromyalgia patients.
The findings described so far are at the core of the Myongji Hospital team’s hypothesis according to which inflammation to the optic nerve may increase in people suffering from fibromyalgia.
The South-Korean study was based on a cohort including all the patients with fibromyalgia from the entire South Korean population aged 20-79, which was compared with a group of people who were experiencing pain but were not diagnosed with fibromyalgia.
Both groups contained 479,892 participants. A logrank analysis was used to compare the risk of optic neuritis incidence between the two groups. Cox proportional hazards regression analysis was performed to calculate the adjusted hazard ratio. The cohort was analysed by stratifying according to age and sex.
This in-depth analysis of the Korean data showed that the incidence rate of optic neuritis in the fibromyalgia group was 35,65/100,000 person-years (a combined ratio of the number of participants and the timeframe during which they are at risk of developing fibromyalgia), whereas the incidence rate dropped dramatically to 16,75/100,000 person-years in the non-fibromyalgia group. The total cumulative incidence rate of optic neuritis in the fibromyalgia group was therefore significantly higher.
Men showed a higher risk of developing optic neuritis in the older age-group (60-70 years of age), whereas women were significantly more at risk in the younger age-group (20-30 years of age).
The results of the study by Hyung Rae Cho, Geung Kyu Lee and Ju-Yeun Lee, despite their undisputable usefulness for studying fibromyalgia, seem to show significant limitations.
The first limitation lies in the lack of information regarding the severity of optic neuritis and fibromyalgia in participants, which prevents researchers from identifying a linear relationship between the severity of the two diseases.
The second limitation is due to the lack of information on the ethnicity of patients, who, according to recent data, were of non-Korean origin only in 1% of cases. This means that results only refer to the Asian population.
The third limitation, and perhaps the most significant, is that patients suffering from fibromyalgia may have been inadvertently included in the non-fibromyalgia group, due to the difficulty in diagnosing fibromyalgia itself.
Despite its limitation, the study proves nevertheless to be very useful in increasing our understanding of the physiopathology of fibromyalgia.
● AJO
