FM and stroke risk

Inspired by Katz et al 2020,[1] and Ma et al 2020.[2]

Photo by Pixabay on – I guess the image was just shouting hazard ratio at me 😉

FM – fibromyalgia

VAS – visual analogue scale

PPT – pressure pain threshold

HR – hazard ratio

key to acronyms

I have a couple of really interesting papers on fibromyalgia (FM) this week – both unique in different ways. The first measured intramuscular pressure in patients with FM using the same device used to assess compartment pressure in the lower leg or forearm in a case of suspected compartment syndrome. You can see a helpful video on how the device is used to assess compartment pressure here.

Intramuscular pressure was measured in the trapezius muscle with a 22G needle inserted 2cm at an angle of 70 degrees. I estimate from a diagram in the paper that the insertion site was near to the acupuncture point TE15, and the angulation was tangential to the upper ribcage in a coronal plane. 108 patients with FM were compared with 30 rheumatological patients without FM. As well as measuring intramuscular pressure in trapezius, they also recorded VAS pain, tenderness to digital palpation, and PPT with a dolorimeter.

Intramuscular pressure was markedly elevated in FM

The average intramuscular pressure in the FM group was 33.48 ± 5.90 mmHg compared with 12.23 ± 3.75 mmHg in the non-FM comparator group. The pressure in the FM group did not vary with gender or age, but correlated very well with pain, tenderness and dolorimetry measures.

This is the first paper I have seen where intramuscular pressure has been measured in anything other than compartment syndrome, and it was a considerable surprise to see such a difference between FM and non-FM groups. The average intramuscular pressure is getting close to the level that one might diagnose a compartment syndrome if it had been in the lower leg or forearm. This led me to wonder whether the result could have been due to background voluntary muscle tension. Even if this was the case, it does give us a target for treatment ie muscle tension. So, it is a useful result. But is it related to the cause of FM or a secondary effect of the condition? I strongly suspect the latter.

The second paper I am highlighting is yet another huge retrospective observational study from Taiwan – another on FM, but this time on the risk of stroke. A paper on the incidence of coronary heart disease in FM, and the risk reduction associated with having acupuncture was published in 2017,[3] but I did not start highlighting these papers until the second one in patients with rheumatoid arthritis (see CHD incidence in RA and acupuncture).[4]

This paper by Ma and colleagues found over 200k patients with newly diagnosed FM between 2000 and 2010 on the nation health insurance database. After exclusions for missing data, identification of those having received acupuncture after a diagnosis of FM, and propensity score matching, the team were left with 65 487 patients in both acupuncture and no acupuncture groups. The database was then examined to see how many had suffered strokes after 2013.

Acupuncture was associated with a reduced risk of stroke in FM

Acupuncture was associated with a reduced risk of stroke (adjusted HR 0.53), which is the sort of result we have come to expect in these observational studies – the risk is roughly halved. I was intrigued to look at the other associations, and the biggest in terms of HR was age, with a 9-fold increase over the age of 65. I also noted a substantial risk reduction associated with NSAIDs (adjusted HR 0.17 – that is more than a 5-fold reduction in risk). But before you all start reaching for your aspirin, the vast majority of these two cohorts were taking NSAIDs (~99%), and they did not look for or report gastrointestinal bleeding and did not differentiate haemorrhagic from the more common thrombotic strokes. Antidepressants were associated with a 2-fold increase in risk of stroke, and statins with a halving of risk.

The mean number of acupuncture sessions was 8.73, and the median was 4, which means that one half of the sample had 4 sessions or less and the other half (or just less than half had around 15 each (on average). It would be interesting to know the HRs for patients who had at least say 10 sessions, since 4 or less seems unlikely to have had a huge impact on stroke risk.

Reference list

1         Katz RS, Leavitt F, Small AK, et al. Intramuscular Pressure is Almost Three Times Higher in Fibromyalgia Patients: A Possible Mechanism for Understanding the Muscle Pain and Tenderness. J Rheumatol 2020;:jrheum.191068. doi:10.3899/jrheum.191068

2         Huang M, Yen H-R, Lin C, et al. Acupuncture decreased the risk of stroke among patients with fibromyalgia in Taiwan: A nationwide matched cohort study. PLoS One 2020;15:e0239703. doi:10.1371/journal.pone.0239703

3         Wu M-Y, Huang M-C, Chiang J-H, et al. Acupuncture decreased the risk of coronary heart disease in patients with fibromyalgia in Taiwan: a nationwide matched cohort study. Arthritis Res Ther 2017;19:37. doi:10.1186/s13075-017-1239-7

4         Wu M-Y, Huang M-C, Liao H-H, et al. Acupuncture decreased the risk of coronary heart disease in patients with rheumatoid arthritis in Taiwan: a Nationwide propensity score-matched study. BMC Complement Altern Med 2018;18:341. doi:10.1186/s12906-018-2384-5

Declaration of interests MC