A topic explored in several studies is the relationship between ME/CFS and hand grip strength (a measure of the force exerted by hand muscles when gripping an object). In 2018, Dr Luis Nacul and team demonstrated in a cohort including 272 ME/CFS participants that not only is hand grip strength reduced in individuals with ME/CFS compared to healthy controls, but those with more severe disease had a significantly greater reduction in hand grip strength.
A recent study conducted by researchers from Charité – Berlin University of Medicine extended the research to individuals with long COVID (referred to as post-COVID syndrome (PCS) in the paper). Specifically, they noted that in the subset of individuals who developed ME/CFS following SARS-CoV-2 (COVID-19) infection, reduction in hand grip strength correlated with disease severity.
What did the study do?
The primary objective of the study was to gain a more comprehensive understanding of the symptom patterns observed in both long COVID and ME/CFS. The researchers aimed to “establish correlations between [hand grip strength] HGS and the levels of functional impairment and symptom severity”.
The study involved 144 female participants diagnosed with post-COVID syndrome (long COVID), “according to the WHO criteria”, of which 78 were further diagnosed with ME/CFS based on the Canadian Consensus Criteria. Thus, there were two cohorts within the study: ME/CFS (78 individuals) and “non-ME/CFS” (66 individuals). Hand grip strength was assessed using a digital hand dynamometer, which measures force generated from squeezing the device’s handle, to objectively measure muscle fatigue. Key symptoms and the “severity of disability” were evaluated using self-reported questionnaires.
What did the study find?
Comparing individuals with long COVID with and without a diagnosis of ME/CFS, “those with ME/CFS had various higher-severity symptoms, including fatigue, [post-exertional malaise] PEM, orthostatic intolerance, vasomotor, and immune symptoms” and experienced greater disability and impairment of physical functioning. Whilst hand grip strength impairment was evident in all participants with long COVID, correlations between level of hand grip strength impairment and severity of key symptoms (PEM, cognitive impairment, fatigue, and orthostatic intolerance) were uniquely observed in the ME/CFS cohort.
Discussion
The study further demonstrates the potential of hand grip strength as an objective measure for physical function in ME/CFS, as even within a study population consisting of individuals with long COVID, correlations between hand grip strength and symptom severity uniquely occur in those meeting ME/CFS criteria. The researchers suggest that the findings point to a common mechanism underlying muscle fatigue and other symptoms in those with post-COVID ME/CFS, distinct from long COVID without ME/CFS. They further state hand grip strength “emerges as an important diagnostic and prognostic tool, enabling an objective evaluation of disability.”
The researchers acknowledge that patients with long COVID not fulfilling ME/CFS criteria “constitute a not-well-defined group, characterized by moderate-to-severe fatigue, exertion intolerance, and cognitive impairment.” They further state that a limitation of the study is the lack of control group, such as those recovered from COVID-19 or with other chronic condition. Another limitation is that the study participants are exclusively female, justified within the paper due to the fact that majority, approximately 75%, of their patient population consisted of women and that comparing hand grip strength between men and women “would not yield meaningful results, given the substantial disparity in strength levels between the sexes”.
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