Grip test results and brain imaging in the NIH study: Deep phenotyping of PI-ME/CFS, 2024, Walitt et al

a techie friend told me that instead of building it from the ground up, they'd just bolted it on top of DOS
For backwards compatibility with old software. So the analogy makes additional sense here given that it's likely adaptations on top of old adaptations that gave us this illness. Genetic and epigenetic changes that allowed more humans to survive some diseases, at the cost of future problems. We inherited all the kludge that allowed our ancestors to survive different conditions, and it gave us a huge technical debt. Which just makes the comparison *chef's kiss*.

I wouldn't stretch the software analogy further given the weird history but yeah it makes sense ;)
 
Can anyone help me make sense of this? Walitt et al. 2024 reported higher max hand grip than Jäkel et al. 2021 despite lower physical function scores.

Mean max hand grip of people with ME/CFS
  • In Jäkel et al. 2021, the mean max hand grip in kg for females with ME/CFS was 18.1 and 31.2 for males (see table 3)
  • In Walitt et al. 2024, the mean max hand grip in kg for 16 PI-ME/CFS was 35.2 (using data for figure 3C). The sex of those 16 is not specified but only one patient was missing and the group was 59% female.
SF36 physical function score
  • In Jäkel et al. 2021, of the females with ME/CFS for whom we have SF36PF, mean is 43. For males with SF36PF data, mean is 49 (excluding one entry error).
  • In Walitt et al. 2024, mean of the group is 32.
There are definitely issues with missing SF36PF data, but it feels like it would take a lot to bridge that gap.

Editing to add:
Note: When I say "higher", "more" etc in these posts, I'm not talking about statistically significant differences, just numerical ones that might be non-negligible. I'm just trying to think out loud, brainstorm, not pronounce anything.

The lack of difference in max voluntary contraction between pwME and controls was important to Walitt et al.'s argument that patients were able to do the movement but preferred not to in the repeated test.
 
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Perhaps there were differences in what was measured e.g. peak maximum, or maximum able to be sustained for a certain amount of time?

It seems to me that hand grip strength is going to vary a lot between people regardless of ME/CFS. Things like hand size, prior training and lifestyle, maybe muscle cell type. When you are working with small samples of people, those differences could easily mask impacts of ME/CFS (or lack of impacts).

I don't think ME/CFS has changed my peak muscle strength on a good day (except as a result of reduced physical activity). I think what it has changed is my ability to generate the same force repeatedly.
 
Perhaps there were differences in what was measured e.g. peak maximum, or maximum able to be sustained for a certain amount of time?
I can't find any info in Walitt et al. 2024 about exactly how they measured it. But I think maximum voluntary contraction is pretty standard.

It's the flipped results I can't get my head around - if Jäkel's subjects had the same sex composition as Walitt's (59% female), then the mean max hand grip for Jäkel's sample would have been 23.5. Walitt's group's mean max hand grip, however, is higher, 35.2. So you think, huh, OK, they were just a stronger group. But that's odd - Walitt et al. sought out moderate-severe patients, and their SF36PF scores would suggest they found them, with a mean SF36PF of 32, lower than Jäkel's 43. Jäkel's group contains many patients with high SF36PFs in the 60s, 70s, 80s and 90s.

It seems to me that hand grip strength is going to vary a lot between people regardless of ME/CFS. Things like hand size, prior training and lifestyle, maybe muscle cell type. When you are working with small samples of people, those differences could easily mask impacts of ME/CFS (or lack of impacts).
Indeed - it remains frustrating that after all that time, we ended up with a study with such a small sample that we can't be confident in negative findings.

I don't think ME/CFS has changed my peak muscle strength on a good day (except as a result of reduced physical activity). I think what it has changed is my ability to generate the same force repeatedly.
Yeah, that's what I notice in everyday life too - a disproportionate difficulty with repeated or sustained activity. (I'm severe though, with a possibly unrelated issue, so my strength is reduced.)

I saw a new doctor recently. I was determined not to just be dismissed as deconditioned and told to exercise. So when he told me to squeeze his fingers, I went for it. He yelped! It worked, though.

Editing to add:
Note: When I say "higher", "more" etc in these posts, I'm not talking about statistically significant differences, just numerical ones that might be non-negligible. I'm just trying to think out loud, brainstorm, not pronounce anything.
 
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if Jäkel's subjects had the same sex composition as Walitt's (59% female), then the mean max hand grip for Jäkel's sample would have been 23.5. Walitt's group's mean max hand grip, however, is higher, 35.2. So you think, huh, OK, they were just a stronger group. But that's odd - Walitt et al. sought out moderate-severe patients, and their SF36PF scores would suggest they found them, with a mean SF36PF of 32, lower than Jäkel's 43. Jäkel's group contains many patients with high SF36PFs in the 60s, 70s, 80s and 90s.
Maybe it's to do with how long people have been sick and therefore how deconditioned they might be. The Walitt study required their participants to have had ME/CFS for less than 5 years, Do we know the duration of illness of participants in the other study?
 
Maybe it's to do with how long people have been sick and therefore how deconditioned they might be. The Walitt study required their participants to have had ME/CFS for less than 5 years, Do we know the duration of illness of participants in the other study?
Good call, Trish. I've been too wrecked to look too closely at baseline characteristics which are likely the answer.

Duration of illhness
  • In Jäkel's study, mean duration of illness for both females and males was 4 years, but with a wide range: 1-32 years for females and 1-42 years for males.
  • In Walitt's study, mean duration of illness was just shy of 3 years (33 months, SD 15).

So if duration of illness explained the paradox, you'd have to argue that patients who are sicker for longer lose muscle strength, but have better physical function overall. Perhaps it would be explained if ME/CFS is, on average, more severe in earlier years. This would be reflected in lower SF36PF scores earlier in the course of illness.

Oooh, I like that, Trish.

The other one that is a likely candidate is age.

Age
  • In Jäkel's study, median age (range) was 49 (21–76) for females, 40 (18–60) for males.
  • In Walitt's study, mean age was 37.8 (SD 14.7) for patients.
Doesn't look like a big difference. I can't think of a reason why slightly older people would have stronger arms. Maybe from years of carrying children!

Note: When I say "higher", "more" etc in these posts, I'm not talking about statistically significant differences, just numerical ones that might be non-negligible. I'm just trying to think out loud, brainstorm, not pronounce anything.
 
For the people digging through the data: There are quite a few other studies by Scheibenbogen et al that also did hand-grip strength testing (some are Post-Covid ME/CFS or just Post-Covid focused), it might be hard to know how all these samples overlap but I just wanted to say that there's additional data from the same team.
 
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