Prevalence of functional somatic syndromes and bodily distress syndrome in the Danish population: the DanFunD study, 2019, Petersen et al

Tom Kindlon

Senior Member (Voting Rights)
https://www.ncbi.nlm.nih.gov/pubmed/31409218

Scand J Public Health. 2019 Aug 14:1403494819868592. doi: 10.1177/1403494819868592. [Epub ahead of print]
Prevalence of functional somatic syndromes and bodily distress syndrome in the Danish population: the DanFunD study.
Petersen MW1, Schröder A1, Jørgensen T2,3,4, Ørnbøl E1, Dantoft TM2, Eliasen M2, Carstensen TW1, Falgaard Eplov L5, Fink P1.
Author information
1
1 The Research Clinic for Functional Disorders and Psychosomatics, Aarhus University Hospital, Denmark.
2
2 Center for Clinical Research and Prevention, Bispebjerg and Frederiksberg Hospital, Denmark.
3
3 Department of Public Health, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
4
4 Faculty of Medicine, Aalborg University, Denmark.
5
5 Mental Health Centre Copenhagen, The Capital Region of Denmark, Denmark.
Abstract

Aims:

Little is known about the prevalence and characteristics of functional somatic syndromes (FSS) such as irritable bowel syndrome (IBS), fibromyalgia (FM), chronic fatigue syndrome (CFS), whiplash associated disorders (WAD), multiple chemical sensitivity (MCS), and bodily distress syndrome (BDS) in the general population when they are investigated simultaneously.

Method
:

This cross-sectional study is based on the Danish Study of Functional Disorders (DanFunD) cohort consisting of 9656 adults from the general population.

FSS and BDS were identified by questionnaires and characterized by age, sex, vocational training, physical health and comorbidity with physical and psychiatric disease.

Results
:

In total, 16.3% (95% CI: 15.6-17.1) of the participants fulfilled the criteria for at least one FSS, ranging from 1.7% for WAD to 8.6% for CFS, and 16.1% (95% CI: 15.4-16.9) fulfilled the criteria for BDS.

Cases had a high risk of poor self-perceived health, limitations in daily activities, and a high psychiatric comorbidity, all increasing with the number of syndromes in each individual.

However, the associations differed across the various FSS.

Mutual overlaps of IBS, FM and CFS were greater than could be expected by chance.

Conclusions:

FSS and BDS are prevalent in the adult Danish population, and cases have high risk of poor self-perceived health, limitation in daily activities, and psychiatric comorbidity.

These associations were particularly strong for cases with multiple FSS and multi-organ BDS.

KEYWORDS:
Irritable bowel syndrome; bodily distress syndrome; chronic fatigue syndrome; fibromyalgia; multiple chemical sensitivity; whiplash associated disorders

PMID:
31409218
DOI:
10.1177/1403494819868592
 
Well, the Danish have convinced the world they have been producing salami for several decades now. Surely this is much the same post-truth Deleuzian, best back, there's more where this came from, handle-turning? The only question is when does it disappear up its own jejunal villi.

But Per-reviewed research - that is a touch of genius.
 
How are those clowns taken seriously? I'm surprised they left TBI and migraines off the list.

Not even bothered with properly diagnosing. Just questionnaires.
Mutual overlaps of IBS, FM and CFS were greater than could be expected by chance.
The cluelessness on display is simply galactic-sized. Absolutely nothing of value can be concluded from such a study.

As otherwise the main takeaway is that according to assumptions made by this kind of researchers, there is currently a massive epidemic of disabling psychogenic illness that affects roughly 1/12 human. Of unspecified origin, or mechanism, or explanation. As long as you keep everything as vague as possible and mix-and-match according to an arbitrary set of beliefs.

It would represent the single largest "disease" in the world, likely affecting close to 10% of the world's economic output. No one describe its mechanism, or anything even remotely related to an explanation. It just exists and the solution is therapy. Because reasons.

Ridiculous. A complete waste of everything.
 
Clearly they have a rather different definition of CFS.


From the participants and methods section:

Symptoms of CFS were rated on a four-point likert scale from ‘less than usual’ to ‘much more than usual’, and symptoms had to be present ‘more than usual’ or ‘much more than usual’ to be included. CFS was assigned to participants scoring at least 4 on the 11-item fatigue scale [21]

From the discussion section:

one study [15] found prevalence of chronic widespread pain and CFS of 9.4% and 12.6%. hence, other studies have overall found higher prevalences for individual syndromes than our study.

...

[15] McBeth J, Tomenson B, Chew-graham C, et al. Common and unique associated factors for medically unexplained chronic widespread pain and chronic fatigue. J Psychosom Res 2015;79:484–91.

I quickly skimmed the referenced study [15]. It seemed a bit muddled and talks mainly about 'chronic fatigue' and some 'CFS-like illness' but at least, unlike the present study, it recognises the limitation that "we did not use an interviewer-based detailed definition of chronic fatigue preventing us from extrapolating our findings to this smaller group of the more severe chronic fatigue syndrome."


They almost had an insight here, but then they go and spoil it again:

Our finding that CFS was most prevalent in the youngest part of the population might be caused by case identification being based on questionnaires, making it difficult to establish genuine, clinical syndrome diagnoses and distinguish them from general but not syndrome-related fatigue. general fatigue might be more prevalent in the younger part of a general population due to establishment of career, housing and family, and work/life balance might be challenged resulting in periodic fatigue. however, since the definition of CFS was based on whether or not the participants experienced symptoms more than usually, it is justifiable to suggest that the identified symptom patterns of CFS are actual reflections of this disorder rather than general consequences of work/life imbalance.

https://sci-hub.se/10.1177/1403494819868592
 
8,6% of the population sample said they had fatigue symptoms more than usual compared to last month, and the authors labelled them as CFS patients
There is supplementary material where they explain how CFS was defined. See: https://journals.sagepub.com/doi/suppl/10.1177/1403494819868592

They only used the Chalder Fatigue Questionnaire as expected but with one difference: they asked about fatigue symptoms in the last 12 months. The CFQ usually asks about symptoms in the last month or when participants were last well. I would be clearer if they had added precisely what the participants were asked- how the questions were formulated.
upload_2019-8-16_13-39-4.png
 
They also report in the paper that "A subgroup analysis was made excluding participants who reported suffering from chronic physical disease which could possibly account for their symptom patterns." They reported this in the supplementary material, in Tables S10–S14 and Figures S2–S3. I suspect there is a mistake in the title of Table S10 and that these are the prevalence rates adjusted for chronic physical disease in both men and women, not just women (which is reported in Table S11).

If that's the case, it's rather strange how little difference, adjustment for chronic physical disease makes to the prevalence rates of the 'syndromes'.
upload_2019-8-16_13-52-52.png
 
I quickly skimmed the referenced study [15]. It seemed a bit muddled and talks mainly about 'chronic fatigue' and some 'CFS-like illness' but at least, unlike the present study, it recognises the limitation that "we did not use an interviewer-based detailed definition of chronic fatigue preventing us from extrapolating our findings to this smaller group of the more severe chronic fatigue syndrome."
Yes, they say that other studies have reported higher prevalence estimates than their study, but that doesn't seem right for CFS. Reference 15 is about unexplained chronic fatigue, which the authors acknowledge is different from CFS: "It is worth noting that chronic fatigue is much more common and relevant to primary care, than chronic fatigue syndrome."

Peterson et al. also write:
our results are similar to a study including a range of FSS [14] using a questionnaire asking participants if they had received a diagnosis of IBS, FM and/or CFS, which found that 11.0% of 89,585 adults sampled from the general population reported having at least one FSS
Reference 14 refers to the LifeLines study by Judith Rosmalen. The figure of 11% they report is of a self-reported lifetime diagnosis of CFS, FM or IBS. But look at the distribution of that 11%: it's very different from what Peterson et al. reported (the number don't add up to 11% because of overlap)
upload_2019-8-17_11-17-9.png
Even if you don't know anything about CFS and how it is diagnosed, if you have read research on FSS it should be obvious that these numbers of the DanFunD do not seem correct. The prevalence of CFS is higher than that of FM and IBS combined!
 
It gets even weirder. Apparently, DanFunD does have a lot of information about its participants. You can read about it here: https://pdfs.semanticscholar.org/7e...1.1480774417.1566033579-2114742670.1563967729

Each participant had a clinical examination. The researchers have blood samples, fitness test results, pain pressure thresholds and much more:
A basic examination routinely conducted in all cohorts at RCPH was included regarding cardiorespiratory fitness (blood pressure, resting heart rate, step test,56 lung function by spirometry, and respiratory rate), morphological fitness (weight, height, waist and hip circumference, and bioelectrical impedance), and muscle fitness (hand grip).
If all participants were clinically examined into detail and some received a telephone-based diagnostic interview, it should be possible to come up with a more realistic definition of CFS than scoring more than 4/11 on the Chalder Fatigue Scale.

In fact, they have data on the self-reported prevalence of the functional somatic syndromes. It's approximately 1,19% for CFS, much lower than the 8,6% reported in their recent study. So they could have either used more information about the participants to come up with a realistic CFS definition or - if that was too difficult - they could have used the 1,19% self-reported CFS.

But instead, they prefer the 8,6% estimate (that's the estimate where even chronic physical diseases that account for fatigue symptoms are not excluded for some reason) which totals 823 CFS patients. I've found some conference abstracts in the Journal of Psychosomatic Research, where Fink's research team seems to use that broad definition of CFS to perform analyses on the valuable data they have on participants of DanFunD.

There's one on lifestyle parameters, which report n = 823 CFS patients, more than the number of FM and IBS patients combined.
https://www.researchgate.net/public...e_general_Danish_population-The_DanFunD_study

One on lipid- and glucose metabolism which also reports n = 823 CFS patients, more than the number of FM and IBS patients combined.
https://www.researchgate.net/public...ts_towards_a_common_genesis_The_DanFunD_study

And one on conditioned pain modulation and pain sensitivity. Here the n for CFS is 187, but it's still more than the number of FM and IBS patients combined. So presumable it's just a subgroup of patients using the same broad definition for CFS.
https://www.researchgate.net/public...unctional_somatic_syndromes_The_DanFunD_study


It would be unfortunate if all this valuable information that was gathered on a representative sample of the Danish population was used to do analyses on a CFS definition that doesn't make much sense.

One could argue that they are simply studying chronic fatigue and just made a mistake in naming it. But that will confuse the literature, much like studies of the empirical criteria (the Reeves definition) have done. I suspect that in future publications that use the broad n = 823 CFS sample of the DanfunD for analyses, it will no longer be clear to readers how this sample was formed, that the prevalence of CFS was 8,6% etc.

Another problem is that, in my view, CFQ scores do not form a good definition of people suffering from chronic fatigue either. They only had some fatigue symptoms more than usual within the last 12 months. Perhaps people were more fatigued because they were renovating their house or just had their first baby. With the CFQ, we don't know anything about the intensity or frequency of fatigue or whether it could be explained by exertion or stressful life events.
 
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It would be unfortunate if all this valuable information that was gathered on a representative sample of the Danish population was used to do analyses on a CFS definition that doesn't make much sense.

One could argue that they are simply studying chronic fatigue and just made a mistake in naming it. But that will confuse the literature, much like studies of the empirical criteria (the Reeves definition) have done. I suspect that in future publications that use the broad n = 823 CFS sample of the DanfunD for analyses, it will no longer be clear to readers how this sample was formed, that the prevalence of CFS was 8,6% etc.
And like all the CFS studies that used Oxford and quite a few with Fukuda. In a review of 53 Fukuda studies, Jason reported that the occurrence of PEM ranged from 25-100 percent of patients in those studies while unrefreshing sleep ranged from 16-100 percent. Both symptoms are required by CCC and IOM for a case of ME and significant in ME-ICC. Its impossible to know what these CFS cohorts are and it just muddles the picture with findings that are best suspect and at worst, erroneous and irrelevant. But they nonetheless can end up in "evidence-based" clinical recommendations
 
Symptoms of CFS were rated on a four-point Likert scale from ‘less than usual’ to ‘much more than usual’, and symptoms had to be present ‘more than usual’ or ‘much more than usual’ to be included. CFS was assigned to participants scoring at least 4 on the 11-item fatigue scale [21].

The logical conclusion is that a score of 4 or more on the Chalder Fatigue Scale is not a specific predictor of CFS. (Note that Chalder reported the cutoff score of 3 or less as indicative of "normal" fatigue using bimodal scoring, not Likert scoring.)

Anyone who has actually looked at the questionnaire knows how incredibly nonspecific this cut off would be.

chalder fq.jpg
 
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Anyone who has actually looked at the questionnaire knows how incredibly nonspecific this cut off would be.

"the only tool a statistician should use on the CFQ is a sharp stick"

Maybe worth noting that the Chalder Fatigue Scale was not included on the list of fatigue instruments recommended as part of NIH's Common Data Elements for ME/CFS.

Screen Shot 2019-08-18 at 7.02.34 PM.png
Explanation of terms... the Core designation is for instruments expected to be used in all studies. The exploratory label is when e.g. not previously used in ME/CFS, needs further validation, etc.
 
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