ME/CFS Epidemiology - sex ratios, female predominance

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That’s a good list and I’m sure that’s the right way to go to really interest people in the field. I think two other findings are worth adding to the list:

The fact that, consistently, around 80% of patients are women. This is pretty unusual, I think. And while more females receive a mental health diagnosis, I thought that typically this was around 2/3, rather than the 80% same for any CFS.

Also, the remarkable “two peaks“ age profile of the honours, with the first peak in adolescence/early adult hood (with the gender difference emerging during puberty) in the second pic starting in people‘s thirties. It’s hard to explain this finding, but it surely a sign that something unusual is going on here.

 

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Yes, I agree. I guess the female predominance has been known for a while so is not so much 'progress'. The double peak would follow point 1. I am not sure that it has been replicated across geography but the emergence of gender predominance in adolescents certainly has.

 

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I think there have only been decent epidemiological studies in the US and the UK. A study on the European mainland, by Euromene for example, would be useful.

I think there's only one study that reported 80% of ME/CFS patients being female; the Wichita, Kansas study (Reyes et al. 2003) which reported 83,2%. Jason et al. said it was more around 70% (23/32) and the study by Nacul in the UK found a much lower figure of around 50%. So I don't know if there's clear differences between the % being female in mental health diagnoses.

I thought that was just one study (Bakken et al. 2014). Does it show in other publications as well?

I would add another finding that has been confirmed by multiple research teams: the prevalence of ME/CFS is increased following infections such as EBV-infection. I think Wessely and others initially thought this was a spurious finding and that ME/CFS patients just wanted to make sense of their symptoms by making that connection with infections. But Peter Whites study showed that the prevalence of ME/CFS increased following EBV-infection while this was not the case for mood disorders such as depression. That seems like an important finding to me.

 

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I’m wondering - taking into account that all of the statistics for this disease are fairly unreliable since studies are small, definitions differ, etc., which statistics do you all consider the most reliable? I am always uncomfortable quoting almost all of them.

I do believe, for example, that there are more women with this disease than men since every study indicates that and it’s consistent with other immune-related diseases, but I’m uncomfortable with the percentages.

How close are we to accurate on any of the stats?

 

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The Nacul 2011 Prevalence study found around 80% female cases for ME/CFS (Table 4 https://bmcmedicine.biomedcentral.com/articles/10.1186/1741-7015-9-91). The huge Norwegian study gives an incidence ratio of 3.2 female cases for every male case (76% female). And just about every mecfs study ever done, covering many thousands of cases, have 75%-80% female cases (I always check). So there does seem to be solid evidence that the female ratio is higher than for psych cases.

As @Jonathan Edwards said, there is at least one UK study replicating the adolescent age peak. As you say, there is just the Norwegian study for the adult peak but that Norwegian study is based on the highly-rated Norwegian health database which covers the National population and is regarded as one is the best sources of health data in the world. It included nearly 6000 cases of ME/CFS. And it confirms what is widely reported by clinicians, an adults peak in the 30s (the data show this is more pronounced for women than for men).

So I think the age peak is pretty robust as well, with strong enough evidence to cite to outside researchers as a reason to take interest in the field.

Agreed, this is also replicated and worth reporting.
Good point. There's also the famous Dubbo study which also shows significant rates of CFS following Ross River virus and Q-fever. Simon Wessley ran a study that find no increase in rates of CFS following common infections, but it was seriously flawed, not least in being hopelessly underpowered to detect credible rates of CFS. So we still don't know about a link between common infections and ME/CFS.

 

Interesting.

Sorry about my mistake. I was misguided because of a graph that was reported in Valdez et al. (2018), the study that tried to use ICD-codes in the US to estimate the prevalence.

They probably looked at table I which gives the demographics of all patients in the clinics studied and I made the same mistake in checking. I also didn't realize the Norwegian study was based on such good data. Thanks for pointing that out.

 

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I would think that being the largest effort of its kind, the IOM report would likely be the most accurate.

Which does not mean it is entirely accurate but likely the most. There is consistency around those numbers as well so if they are off it's likely to not be by much in %.

 

I agree that the ratio is not necessarily convincing, but I am thinking that doctors expect it in women and not in men, so more women get diagnosed (and computers learn to expect this so predict that outcome).

When we know the vast majority of people are undiagnosed (and in other studies, people are overdiagnosed but oddly enough probably still not diagnosing many cases, as they may exclude people with nurological signs for example), it's hard to generalize demographics.

 

I was thinking, if this finding would turn out to be true, perhaps it tells us something about the heterogeneity of ME/CFS.

If a predominance of 80% of women is rather unusual in medicine, it might make it unlikely that ME/CFS is a broad collection of different illnesses. Cause it would be quite a coincidence that practically all those illnesses have that unusual predominance of 80% of women. That would be like multiplying an unlikely chance to get a much lower chance. You want to make that multiplication as little as possible because the chance becomes improbable very quickly. If a ratio of 4/5 women is really unusual in medicine, it would be statistically more reasonable to assume that there are few rather than many of these illnesses making up ME/CFS. And if some of those underlying illnesses have a lower female/male ratio, than it would require the other illnesses making up ME/CFS to have an even larger predominance of women than that 80%, which also seems unlikely.

So perhaps the fact that almost 80% of ME/CFS patients are women forms a weak and uncertain but nonetheless an argument against large heterogeneity of illnesses within the ME/CFS label.

PS: Sorry if this doesn't make any sense at all. It's really hot in Belgium right now...

 

Roughly 80% of those diagnosed with autoimmune diseases are female. This article puts the figure at 77%. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3328995/
I'm not sure if that's collectively or if it holds true for each autoimmune disease.

On the other hand, ~80% of autism cases are male.

Without a biomarker, though, other factors could tilt the apparent prevalence by sex in ME/CFS. For example, doctors might diagnose women more readily than men, and/or men might actively avoid a diagnosis to a greater degree than women.

The M/F ratio may also vary by severity. There might be an increased percentage of men among very severe cases, but I have no idea if that's been borne out by any kind of study.

 

Autism presents differently in females and support services are only now getting to grips with this- very slowly. (similar to how females present differently with heart attacks etc - the whole gender ratio may be changing as more research becomes gender balanced) The male /female ratio may be subject to change in future.

 

This study found that 30% of those diagnosed with “CFS/ME” were male which is a little higher than what tends to see in ME/CFS patient organisations. I couldn’t find the number directly on a quick search but calculated it from a female:male ratio of 2.35:1.

https://www.ncbi.nlm.nih.gov/m/pubmed/28358988/?i=5&from=white crawley collin

Trends in the incidence of chronic fatigue syndrome and fibromyalgia in the UK, 2001-2013: a Clinical Practice Research Datalink study.
Collin SM, et al. J R Soc Med. 2017.

Authors
Collin SM1, Bakken IJ2, Nazareth I3, Crawley E1, White PD4.

 

Meh, Crawley and White. Unreliable.

 

Additionally, many autistic people don't see their autism as a disease. If they have GI problems, they want medical treatment for that. But their autism is just a different way of thinking, like being an introvert or extrovert. They want services and supports to figure out how to navigate a world that doesn't appreciate or understand them, but they don't see autism as a medical issue.

 

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Another 2.4 year prospective study. (mean baseline age of entire population was 44.9, 57% women)

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3427300

New onset 0.08%/year, mean age of 48.0. 56% of new cases were women.

"Lifetime diagnosis at baseline" was 1.3%. (note this was self-reported)

 

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Study was cohort participatory and not observational and generally reflects who participates in these studies uncompensated. I do not have any comments on it directly other than the context I posited above.

 

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I think this study just shows that self-reported diagnosis of CFS is not very reliable. It does make me wonder who all those people are that report a diagnosis of CFS because there seems to be more of them than what one would expect.

Could you explain what you mean by this? The study said that "The sample population of the Lifelines study is broadly representative of the total Dutch population." Mean baseline age was 44.9 with a large standard deviation of 13.2. I think it includes all ages older than 18.