"a gradual decline in recorded diagnoses of CFS/ME since 2001"?

The quote forming the title of today's post comes from the paper by Simon Collin and colleagues [1] (open-access available here) who, based on analysis of the UK "Clinical Practice Research Datalink (CPRD), formerly known as the General Practice Research Database (GPRD)" set out to look at the "Incidence of CFS/ME [chronic fatigue syndrome/ myalgic encephalomyelitis], FM [fibromyalgia], post-viral fatigue syndrome (PVFS), and asthenia/debility." I say incidence but that last sentence should really read as  'recorded incidence'.

Searching the research database between January 2001 and December 2013, researchers looked at the [recorded] incidence (that's incidence not prevalence) of the various fatigue-related conditions/labels recorded by participating GP (general practice) surgeries.

Recorded diagnoses of CFS/ME showed a soft but noticeable decline over the period of study: "Annual incidence of CFS/ME decreased from 17.5 [per 100,000 people] in 2001 to 12.6 in 2013." A similar decline was also noted in respect of PVFS and asthenia/debility. When however it came to FM, there was an overall increase in cases between 2001 and 2013 (albeit characterised by peaks and troughs in recorded diagnoses across specific years).

Some other important data were also reported on. So: "All diagnoses showed strong evidence of variation by age and sex" and estimated socio-economic status (SES). Further: "Incidence rates of CFS/ME were 2.4-fold higher among women... with peak incidence in the 40–49 years age group." Women were also more likely to be over-represented in relation to a diagnosis of FM too.

This is potentially important data. It suggests that at least among participating GP practices in the CPRD, recorded diagnoses of CFS/ME seem to be going down. The caveats however mentioned by the researchers do need to be highlighted, not least that they "examined recorded data rather than actual incidence, i.e. we are describing incidence rates of GPs’ recording of diagnostic codes" and "diagnoses were not independently validated." In other words, this is data based on "GPs enter[ing] medical diagnoses and symptoms as Read codes." I might also add in another quote from the authors too: "In 2005, 48% of GPs in one English region did not feel confident about making a diagnosis of CFS/ME, and 28% did not recognise CFS/ME as a legitimate illness." A bit of an issue by all accounts if one would like to get accurate data on incidence or prevalence.

I also have a to raise a point in relation to this latest data and how it compares with other data produced by the same research group (see here). Keeping in mind that incidence is not the same as prevalence, I bring back to your attention the findings reported by Collin and colleagues [2] on another occasion suggesting that nearly 2% of 16-year olds in the ALSPAC cohort were affected by CFS. More work needs to be done when it comes to official monitoring of the numbers of cases of CFS/ME (and FM) outside of just reliance on GP practice recordings in order to get a true picture of numbers of cases. Of course, there is another possible explanation for the fall in recorded diagnoses: GPs are increasingly understanding that some of the symptoms included under the banner of CFS/ME overlap with various other conditions/labels too...

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[1] Collin SM. et al. Trends in the incidence of chronic fatigue syndrome and fibromyalgia in the UK, 2001-2013: a Clinical Practice Research Datalink study. J R Soc Med. 2017 Jan 1:141076817702530.

[2] Collin SM. et al. Chronic Fatigue Syndrome at Age 16 Years. Pediatrics. 2016 Feb;137(2):e20153434.

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Collin SM, Bakken IJ, Nazareth I, Crawley E, & White PD (2017). Trends in the incidence of chronic fatigue syndrome and fibromyalgia in the UK, 2001-2013: a Clinical Practice Research Datalink study. Journal of the Royal Society of Medicine PMID: 28358988