ME/CFS Epidemiology - sex ratios, female predominance

In the sense of the potential that various theories require you to be unlucky enough to take a big enough hit of 'something', perhaps when your body was vulnerable or you weren't in a situation you could recover well then I guess there is the probability roll-over of more years = more chances to be in that situation.

But then you think about whether peak times involve being around infections (and covid) and whilst we used to think school, uni, and having children at home to give you said bugs I guess Covid has reminded us of care homes being another one. If that was the case though then you'd perhaps have a difference between those in a care home and not. From what I've seen of recent stories of the healthcare system and gut feeling says for various reasons most wouldn't be in a care home until they had to it does seem like ME/CFS diagnoses 'on top' would be the last thing anyone was running around to bother making a diagnosis for though.

So in conclusion I'm actually really intrigued to see more about what is underneath that data for the older age groups.

I've met someone who was 75 and definitely got Long Covid, but I'm not hearing that clinics are keen to even then diagnose those from covid with ME/CFS anyway (I don't know about GPs?)

Particularly given that recent paper about 'MUS vs MES' (medically explained symptoms) in older people: Latent profile analysis of biopsychosocial measures in older patients with (un)explained persistent somatic symptoms 2024 Bos et al | Science for ME (s4me.info)

Where they suggested 'might as well treat em all the same' because those who had 'MES' treatment were no more satisfied outcome-wise (I mean after all everyone is happier if you just reassure them it's nothing serious when they were worried it might be cancer or something) ... which would lead to 'treat them all as if they had MUS'.

That one might have been from the Netherlands, but I wouldn't put it past given recent 'feel' there is a lot of push towards 'functional' diagnoses recently here that there isn't a coding thing..


I guess the main check for this (which is often hard because it isn't there) would theoretically be to check back over many years to see if it is consistent over time or if there start to be jumps or slow surges which might indicate the impact of intiatives etc.

 

There is another point here I have just thought of.

Due to the misleading 'recovery' assumption I think something that has been coming through from enough people writing about their experiences is that you don't go to the GP for a while (because they can't help or nothing has changed, or you are just scared) and they 'assume' that your 'CFS' self-resolved.

I'd love to have this confirmed by someone who knows how these records work but I wouldn't put it past being a situation where instead of that old 'lapsed' diagnosis then being updated, a new one then just gets added. Particularly if there has been the records digital upload thing and someone didn't want to go through decades of paper files to find the original.

I'm just wondering whether there is a chance that people who previously didn't go to the GP then perhaps might having to go around those ages for the first time again as health gets worse or other things crop up - and these 'new' get added because people mention they've had it for 30yrs but it gets added as if it is new?

 

Norwegian Patient Registry studies
Bakken: 74% female, ratio 3.2:1, 5,810 G93.3 cases, hospital diagnosis
Hilland: 79% female, ratio 3.7:1, 5,560 G93.3 cases, hospital diagnosis

These two studies used the same methodology, with Hilland looking at data several years later than Bakken. Both used G93.3 coding to define ME/CFS cases, and the National Patient Registry which covers all hospitalisations and outpatient visits for the entire Norwegian population. The studies focused on incidence by age and sex, but also calculated an overall sex ratio.

The studies differ in two findings. Hilland (data from 2016-18) found a higher proportion of women than Bakken (data from 2008-16) i.e 79% versus 74%, and a higher substantially higher rate of diagnosis: 36 vs 28/100k. The question is, why?

A couple of things appear likely:

1. Increased awareness of ME/CFS amongst patients and doctors
In 2011, Fluge and Mella published the stunning finding of their Rituximab pilot study. This led to even more publicity in Norway than elsewhere, which was boosted by Dr Maria Gjerpe’s MEandYOU remarkable media campaign to raise funds for further research. There was a lot of debate in Norway’s media, and even an apology from a Government minister to patients for the neglect of the illness.

Increased awareness amongst patience and doctors is likely to have led to increased referral to hospital, as Hilland et al suggest.

2. 2014 official guidelines of how to diagnose and code ME/CFS
In 2014, the National Directorate of Public Health, where Inger Bakken is a senior adviser, issued the first national guidelines for ME/CFS advising on correct diagnosis including excluding alternative explanations, and the need to code with G93.3. This is likely to have improved accuracy of diagnosis and may be behind the increase in sex ratio.

 

Summary of big data studies: sex ratios and percentages



Links & Notes
Bakken, 2014 National Patient Register (NPR)
Valdez, 2019 50m with active insurance, multiple providers, SE USA. Uses ICD-CM 9&10; different from Euro ICD usage
Hilland, 2022 NPR, after 2014 national ME/CFS guidelines inc diagnosis guidance issued
Samms, 2024 NHS outpatient data, includes a small number of inpatient cases


Note the x-axis starts at 50% representing no female skew.

I have graphed percentages because they are a linear scale (small percentage differences at high levels map to much bigger differences in sex ratios).