Endometriosis and ME/CFS

It is often suggested that rates of endometriosis are higher in women with ME/CFS than in women in general. I thought it would be useful to put the evidence we have for or against the idea in one place.

 

There was a UK MEA survey, I'm not sure how many people/women answered. It was reported that 15.5% of the respondents said that they had endometriosis. I don't know if that percentage was of women answering or of all people answering. The prevailing rate of endometriosis in women after puberty and before menopause in the UK is reported as around 10%. It's not uncommon.

That does suggest a higher incidence, although a lot of women don't have endometriosis. Issues with self-reporting; and possibly women with ME/CFS might have a high rate of investigation for endometriosis, when trying to find answers. There's also the possibility that women with endometriosis might get incorrectly labelled as having CFS due to some overlap in symptoms.

 

Endometriosis: A Retrospective Analysis of Clinical Data from a Cohort of 4,083 Patients, With Focus on Symptoms, 2022, Signorile et al

There is this study of women with endometriosis. It concluded oddly that:

Members of the forum weren't very impressed. The authors seemed to be confused about chronic fatigue and chronic fatigue syndrome, and there were questions about who was being diagnosed with endometriosis. I'm not sure we can conclude much more from this study other than fatigue is a symptom of endometriosis. Therefore, it's possible that there is misdiagnosis (or the conditions really are related in some way).

 

Early menopause and other gynecologic risk indicators for CFS in women, 2015, Boneva, Lin, Unger
A study of 157 women in Georgia, US, based on a self-administered questionnaire. It found

The wider study of which this was a subset used a very loose CFS criteria, finding a prevalence of CFS of over 2.5%. So, it's highly likely that the sample included a lot of women who would not qualify for an ME/CFS diagnosis with a stricter criteria. Also, the reliance on self-reporting is not ideal.

 

This is an earlier study related to the one above:
Gynecological history in chronic fatigue syndrome: a population-based case-control study, 2010, Boneva, Reeves et al
Kansas, US sample - 36 women with CFS (Reeves criteria - loose), and 48 'non-fatigued controls'.

It's not hard to poke holes in this study - it's too small, and the ME/CFS diagnostic criteria is too loose. Also, if fatigue is a common symptom of endometriosis, which it is, then the rate of endometriosis in the 'non-fatigued controls' probably understates the population-wide prevalence.

It's interesting to see the rate of endometriosis in those 48 non-fatigued controls - it's surprisingly high at nearly 17%.

 

Co‐occurrence of immune‐mediated conditions and endometriosis among adolescents and adult women, Shafrir et al, 2021

The sample of (mostly young) women with endometriosis was well characterised:

It reported odds of women with various conditions having co-occurring endometriosis e.g.
chronic fatigue syndrome and/or fibromyalgia (OR:5.81; CI:1.89‐17.9)

The problem here is that the information about the illnesses was from a self-report questionnaire, and the study seems to use 'chronic pain/fatigue' as a synonym for CFS and fibromyalgia. There's a paywall, so it's hard to be sure, but it might just be that fatigue is common in endometriosis.

 

frontiers in Pediatrics: Endometriosis as a Comorbid Condition in Chronic Fatigue Syndrome by Boneva, Unger et al 2019
2019 study -
The abstract suggests that there were 36 women with CFS and 48 controls. It looks as if this 2019 paper is a re-hash of the 2010 study above. It's just as under-powered in 2019 as it was in 2010.

Fukuda criteria. Difference only just squeaks in as statistically valid.

Among the comments on this paper in the linked thread was a discussion of reported population-wide rates of endometriosis.

 

Yes, but I think the Unger etc papers noted above have played a larger part in spreading that idea than the sample size and strictness of criteria of the studies warrant.

 

In Norway it takes ~five years on average to get an endometriosis diagnosis. I don't doubt many are misdiagnosed with something else along the way. And chronic fatigue gets conflated with chronic fatigue syndrome.

 

Yet another example where the name 'Chronic Fatigue Syndrome' is frequently conflated with fatigue, to the detriment of proper understanding of ME/CFS.

Are any of these studies based on large properly representative sampling epidemiological studies?

 

I think the answer to that is 'no'. Some studies are ridiculously small and probably have biased selection criteria. All poorly characterise ME/CFS, either mixing it up with self-reported chronic fatigue or applying loose criteria. In some studies, endometriosis is poorly characterised.

It's possible that endometriosis is more common in women with ME/CFS than in the general female population. But I think it's still also possible that it isn't.

If anyone knows of any good relevant studies, please do post a note here.