Discussion of full IOM report

"PEM in the IOM report (2) The IOM team clearly carried out an exhaustive literature search (hard work since there isn't that much focusing on PEM, and many of the findings come from studies with other primary aims). For example: PEM exacerbates a patient’s baseline symptoms and, in addition to fatigue and functional impairment ), may result in flu-like symptoms (e.g., sore throat, tender lymph nodes, feverishness) (VanNess et al., 2010); pain (e.g., headaches, generalized muscle/joint aches) (Meeus et al., 2014; Van Oosterwijck et al., 2010); cognitive dysfunction (e.g., difficulty with comprehension, impaired short-term memory, prolonged processing time) (LaManca et al., 1998; Ocon et al., 2012; VanNess et al., 2010); nausea/ gastrointestinal discomfort; weakness/instability; light-headedness/vertigo; sensory changes (e.g., tingling skin, increased sensitivity to noise) (VanNess et al., 2010); depression/anxiety; sleep disturbances (e.g., trouble falling or staying asleep, hypersomnia, unrefreshing sleep) (Davenport et al., 2011a); and difficulty recovering capacity after physical exertion (Davenport et al., 2011a,b). While it's a big symptom list, I like the Canadian Criteria approach of focusing on how it's each patient's characteristic symptom cluster that flares with PEM Canadian Criteria said: Post-Exertional Malaise and/or Fatigue: There is an inappropriate loss of physical and mental stamina, rapid muscular and cognitive fatigability, post exertio1nal malaise and/or fatigue and/or pain and a tendency for other associated symptoms within the patient's cluster of symptoms to worsen. This Van Ness study Postexertional malaise in women with chronic fatigue syndrome (n=25) has good tracking of symptoms flaring after a maximal exercise test vs healthy controls, as does this one by Jo Nijs/Van Oostewjick (n=22) after submaximal exercise. (Would be nice to have bigger studies and I hope that will happen in future.) But I particularly like the Lights' work looking at gene expression after moderate exercise where they also tracked PEM/fatigue, especially as they used an MS comparison group: the differences with MS are marked. I based the graph below on the original data, but simplified for readability (and because I think copyright restrictions may prevent me reproducing the original). The lower of each pair of lines is for mental fatigue, upper is physical fatigue; pain (not shown) followed a similar pattern but at a lower than mental fatigue. Scores are 0-100, self-rated. Differences in metabolite-detecting, adrenergic, and immune gene expression following moderate exercise in chronic fatigue syndrome, multiple sclerosis and healthy controls (White 2012) white-2012-PEM-graph.gif (view original graph) Maybe IOM weren't allowed to reproduce the graph either but they cited the study numerous times re PEM. PEM after cognitive exertion The best evidence for PEM comes after physical exertion, maximal or moderate. The situation after cognitive exertion is mixed, according to research covered by the IOM. A Cockshell & Mathias study foudn that after a 2-hour neurocognitive battery of tests controls recovered fully after 7 hours on average compared with 57 hours for CFS patients. Not everyone finds such affects, though this might be because people have different PEM thresholds. While a maximal exercise test is likely to push all to PEM, and even a 'moderate' one (70% max heart rate) is likely to affect most, there isn't such an obvious cognitive challenge. At the CMRC conference last autumn, Andrew Lloyd said his group were going to use a driving simulator as a more intensive cognitive challenge - will be interesting to see how this pans out. PEM in other illnesses Depending on how it's defined, up to19% of healthy controls recorded PEM, though this falls to 2-7% if stricter criteria are used. By contrast it's very high for CFS patients, even for those defined by Fukuda. One study found 19-20% of depressed patients recorded PEM, another found 64% for depressed patients, but as the report said it's not clear how it was measured. A Komaroff study from 1996 found PEM in 52% of MS patients, which is why I like the White graph above carefully tracking patients after an exercise challenge. Objective measures of PEM There's a great summary of this from Julie Rehmeyer in her New York Times Op-Ed that's a lot easier to read than the IOM report: Unfortunately, no one test can reliably distinguish patients who have chronic fatigue syndrome from those who don’t. The closest thing to a reliable, objective test is a two-day exercise-to-exhaustion challenge on a stationary bike. Sick patients of all varieties may poop out quickly on Day 1 but whatever they do, they can generally repeat it the next day. Not C.F.S. patients; their performance tanks. Physiological measures ensure that the results can’t be faked, and so far, researchers haven’t seen similar results in any other illness. But large studies haven’t been done. The test also has a big problem. It can leave patients much sicker for months. Oh, did I mention that's my blog Julie kindly links to? (New Exercise Study Brings Both Illumination and Questions) I'm pretty sure this section of the IOM report was written by Betsy Keller, who I interviewed for the blog, so same info in a slightly more digestible form. The IOM concludes re CPET: IOM said: By contrast, a single CPET may be insufficient to document the abnormal response of ME/CFS patients to exercise (Keller et al., 2014; Snell et al., 2013). Although some ME/CFS subjects show very low VO2max results on a single CPET, others may show results similar to or only slightly lower than those of healthy sedentary controls (Cook et al., 2012; De Becker et al., 2000; Farquhar et al., 2002; Inbar et al., 2001; Sargent et al., 2002; VanNess et al., 2007). Thus, the functional capacity of a patient may be erroneously overestimated and decreased values attributed only to deconditioning. Repeating the CPET will guard against such misperceptions given that deconditioned but healthy persons are able to replicate their results, even if low, on the second CPET."

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PEM