Unravelling shared mechanisms: insights from recent ME/CFS research to illuminate long COVID pathologies

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic illness often triggered by an initiating acute event, mainly viral infections. The transition from acute to chronic disease remains unknown, but interest in this phenomenon has escalated since the COVID-19 pandemic and the post-COVID-19 illness, termed 'long COVID' (LC). Both ME/CFS and LC share many clinical similarities. Here, we present recent findings in ME/CFS research focussing on proposed disease pathologies shared with LC. Understanding these disease pathologies and how they influence each other is key to developing effective therapeutics and diagnostic tests. Given that ME/CFS typically has a longer disease duration compared with LC, with symptoms and pathologies evolving over time, ME/CFS may provide insights into the future progression of LC.

Parent screening questionnaires to detect cognitive and language delay at 2 years in high-risk infants: an analysis from the Victorian Infant Collaborative Study 2016-2017 cohort

OBJECTIVE

To determine the accuracy of two developmental screening questionnaires to detect cognitive or language delay, defined using the Bayley Scales of Infant and Toddler Development-Third Edition (Bayley-III), in children born extremely preterm (EP: <28 weeks' gestation) or extremely low birth weight (ELBW: <1000 g).

DESIGN

Prospective cohort study.

SETTING

State of Victoria, Australia.

PATIENTS

211 infants born EP/ELBW assessed at 2 years' corrected age (mean 2.2, SD 0.2).

MAIN OUTCOME MEASURES

Cognitive and language delay (<-1 SD) on the Bayley-III. The screening questionnaires were the Parent Report of Children's Abilities-Revised (PARCA-R) and the Ages & Stages Questionnaires Third Edition (ASQ-3).

RESULTS

The PARCA-R performed better than the ASQ-3, but neither questionnaire had substantial agreement with the Bayley-III to detect cognitive delay; kappa (95% CI): PARCA-R 0.43 (0.23, 0.63); ASQ-3 0.15 (-0.05, 0.35); sensitivity (95% CI): PARCA-R 70% (53%, 84%) ASQ-3 62% (47%, 76%); specificity (95% CI): PARCA-R 73% (60%, 84%) ASQ-3 53% (38%, 68%). When both tools were used in combination (below cut-off on at least one assessment), sensitivity increased to 78% (60%, 91%) but specificity fell to 45% (29%, 62%). Similar trends were noted for language delay on the Bayley-III, although kappa values were better than for cognitive delay.

CONCLUSIONS

Neither screening questionnaire identified cognitive delay well, but both were better at identifying language delay. The PARCA-R detects delay on the Bayley-III more accurately than the ASQ-3. Sensitivity for detecting delay is greatest when the PARCA-R and ASQ-3 were used in combination, but resulted in lower specificity.

Diagnostic accuracy of small-for-gestational-age status for infant mortality and school-age outcomes of live births <28 weeks' gestation: a cohort study

OBJECTIVES

To determine the diagnostic accuracy of small-for-gestational-age (SGA; <10th centile) status for infant mortality and adverse school-age outcomes in infants born extremely preterm (EP; <28 weeks' gestation).

DESIGN

Geographical cohort studies.

SETTING

The state of Victoria, Australia.

PATIENTS

For mortality, live births 22-27 weeks' gestation from 2009 to 2017 offered active care after birth. For school-age outcomes, survivors to 8 years' corrected age born in 1991-1992, 1997 or 2005.

EXPOSURES

SGA <10th centile on four commonly used growth references: three derived from neonatal data (Fenton, UK-WHO and Intergrowth Newborn Size) and one from fetal data (Intergrowth Estimated Fetal Weight).

MAIN OUTCOME MEASURES

(a) Infant mortality; (b) major neurodevelopmental disability, and poor performance on tests of IQ, academic achievement, motor function, and executive function.

RESULTS

Infant mortality data were available for 2040 infants, and neurodevelopmental data for 499 children. Diagnostic accuracy of SGA status was low overall and varied with the growth reference. Positive predictive values for infant mortality ranged from 18% to 21%, only marginally higher than its 18% prevalence. Compared with a prevalence of 17%, positive predictive values for major neurodevelopmental disability ranged from 30% to 38% for the neonatal growth references but was only 20% for Intergrowth Estimated Fetal Weight. SGA status was also associated with lower IQ, poor academic achievement and poor motor performance.

CONCLUSIONS

Among infants born EP, the diagnostic accuracy of SGA status was low for both infant mortality and adverse neurodevelopmental outcomes at school age, but importantly varied with the growth reference used to identify SGA status.

What lies beneath: White matter microstructure in pediatric myalgic encephalomyelitis/chronic fatigue syndrome using diffusion MRI

Recent studies in adults with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) suggest that changes in brain white matter microstructural organization may correlate with core ME/CFS symptoms, and represent a potential biomarker of disease. However, this has yet to be investigated in the pediatric ME/CFS population. We examined group differences in macrostructural and microstructural white matter properties, and their relationship with clinical measures, between adolescents recently diagnosed with ME/CFS and healthy controls. Forty-eight adolescents (25 ME/CFS, 23 controls, mean age 16 years) underwent brain diffusion MRI, and a robust multi-analytic approach was used to evaluate white and gray matter volume, regional brain volume, cortical thickness, fractional anisotropy, mean/axial/radial diffusivity, neurite dispersion and density, fiber density, and fiber cross section. From a clinical perspective, adolescents with ME/CFS showed greater fatigue and pain, poorer sleep quality, and poorer performance on cognitive measures of processing speed and sustained attention compared with controls. However, no significant group differences in white matter properties were observed, with the exception of greater white matter fiber cross section of the left inferior longitudinal fasciculus in the ME/CFS group compared with controls, which did not survive correction for intracranial volume. Overall, our findings suggest that white matter abnormalities may not be predominant in pediatric ME/CFS in the early stages following diagnosis. The discrepancy between our null findings and white matter abnormalities identified in the adult ME/CFS literature could suggest that older age and/or longer illness duration influence changes in brain structure and brain-behavior relationships that are not yet established in adolescence.

Hypothalamus volumes in adolescent Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): impact of self-reported fatigue and illness duration

Adolescent Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex illness of unknown aetiology. Emerging theories suggest ME/CFS may reflect a progressive, aberrant state of homeostasis caused by disturbances within the hypothalamus, yet few studies have investigated this using magnetic resonance imaging in adolescents with ME/CFS. We conducted a volumetric analysis to investigate whether whole and regional hypothalamus volumes in adolescents with ME/CFS differed compared to healthy controls, and whether these volumes were associated with fatigue severity and illness duration. 48 adolescents (25 ME/CFS, 23 controls) were recruited. Lateralised whole and regional hypothalamus volumes, including the anterior-superior, superior tubular, posterior, anterior-inferior and inferior tubular subregions, were calculated from T1-weighted images. When controlling for age, sex and intracranial volume, Bayesian linear regression models revealed no evidence for differences in hypothalamus volumes between groups. However, in the ME/CFS group, a weak linear relationship between increased right anterior-superior volumes and fatigue severity was identified, which was absent in controls. In addition, Bayesian quantile regression revealed a likely-positive association between illness duration and right superior tubular volumes in the ME/CFS group. While these findings suggest overall comparability in regional and whole hypothalamus volumes between adolescents with ME/CFS and controls, preliminary evidence was identified to suggest greater fatigue severity and longer illness duration were associated with greater right anterior-superior and superior-tubular volumes, respectively. These regions contain the anterior and superior divisions of the paraventricular nucleus, involved in the neuroendocrine response to stress, suggesting involvement in ME/CFS pathophysiology. However, replication in a larger, longitudinal cohort is required.

Spatiotemporal gait variables and step-to-step variability in preschool-aged children born < 30 weeks' gestation and at term in preferred speed, dual-task paradigm, and tandem walking

BACKGROUND

Children born very preterm (< 32 weeks' gestation) are at greater risk of motor impairment and executive/attentional dysfunctions than term-born children; however, little is known about how functional tasks, including walking, may be affected by very preterm birth.

RESEARCH QUESTION

How does the gait pattern of preschool-age children born < 30 weeks compare with term-born controls under a variety of walking conditions?

METHODS

In this prospective cohort study, children born < 30 weeks and at term were assessed at 4.5-5 years' corrected age, blinded to birth group. Four walking conditions were assessed using the GAITRite® system: preferred speed, cognitive dual-task, motor dual-task, and tandem walking. Gait variables analysed included speed, cadence, step length, step time, base of support (BOS), and single and double support time. Spatiotemporal variables were compared between groups using linear regression, adjusting for lower-limb length, corrected age at assessment, and number of trials.

RESULTS

224 children (112 < 30 weeks and 112 term-born) were assessed. Gait variables of children born < 30 weeks did not differ from their term-born peers when walking at their preferred speed, except for higher BOS variability (mean difference [MD] = 0.19 cm, 95% confidence interval [CI] 0.10, 0.27, p < 0.001). Under the motor dual-task condition, children born < 30 weeks walked faster (MD= 3.06 cm/s, 95% CI 0.14, 5.97, p = 0.040), with a longer step length (MD= 1.10 cm, 95%CI 0.19, 2.01, p = 0.018), and a wider BOS (MD= 0.37 cm, 95%CI 0.06, 0.67, p = 0.019). In cognitive dual-task and tandem conditions, children born < 30 weeks walked with a wider BOS compared with term-born peers (MD= 0.43 cm, 95%CI 0.05, 0.81, p = 0.028; and MD= 0.30 cm, 95%CI 0.09, 0.51, p = 0.005, respectively).

SIGNIFICANCE

This research highlights the need to consider the walking performance of preschool-age children born < 30 weeks under challenging conditions, such as dual-task or tandem walking, when assessing gait patterns and planning interventions.

Temporal Trends in Neurodevelopmental Outcomes to 2 Years After Extremely Preterm Birth

Importance

Survival of infants born extremely preterm (EP) (<28 weeks' gestation) has increased since the early 1990s. It is necessary to know whether increased survival is accompanied by increased neurodevelopmental disability.

Objective

To examine changes in major (ie, moderate or severe) neurodevelopmental disability and survival free of major neurodevelopmental disability at 2 years in infants born EP.

Design, Setting, and Participants

Four prospective longitudinal cohort studies comprising all EP live births at 22 to 27 weeks' gestation from April 1, 2016, to March 31, 2017, and earlier eras (1991-1992, 1997, and 2005), and contemporaneous term-born controls in the state of Victoria, Australia. Among 1208 live births during the periods studied, data were available for analysis of 2-year outcomes in 1152 children: 422 (1991-1992), 215 (1997), 263 (2005), and 252 (2016-2017). Data analysis was performed from September 17, 2020, to April 15, 2021.

Exposures

Extreme preterm live birth.

Main Outcomes and Measures

Survival, blindness, deafness, cerebral palsy, developmental delay, and neurodevelopmental disability at 2 years' corrected age. Developmental delay comprised a developmental quotient less than -1 SD relative to the control group means on the Bayley Scales for each era. Major neurodevelopmental disability comprised blindness, deafness, moderate to severe cerebral palsy, or a developmental quotient less than -2 SDs. Individual neurodevelopmental outcomes in each era were contrasted relative to the 2016-2017 cohort using logistic regression adjusted for gestational age, sex, birth weight z score, and sociodemographic variables. Changes in survival free of major neurodevelopmental disability over time were also assessed using logistic regression.

Results

Survival to 2 years was highest in 2016-2017 (73% [215 of 293]) compared with earlier eras (1991-1992: 53% [225 of 428]; 1997: 70% [151 of 217]; 2005: 63% [170 of 270]). Blindness and deafness were uncommon (<3%). Cerebral palsy was less common in 2016-2017 (6%) than in earlier eras (1991-1992: 11%; 1997: 12%; 2005: 10%). There were no obvious changes in the rates of developmental quotient less than -2 SDs across eras (1991-1992: 18%; 1997: 22%; 2005: 7%; 2016-2017: 15%) or in rates of major neurodevelopmental disability (1991-1992: 20%; 1997: 26%; 2005: 15%; 2016-2017: 15%). Rates of survival free of major neurodevelopmental disability increased steadily over time: 42% (1991-1992), 51% (1997), 53% (2005), and 62% (2016-2017) (odds ratio, 1.30; 95% CI, 1.15-1.48 per decade; P < .001).

Conclusions and Relevance

These findings suggest that survival free of major disability at age 2 years in children born EP has increased by an absolute 20% since the early 1990s. Increased survival has not been associated with increased neurodevelopmental disability.

Investigating the brain structural connectome following working memory training in children born extremely preterm or extremely low birth weight

Children born extremely preterm (EP, <28 weeks' gestation) or extremely low birth weight (ELBW, <1,000 g) are a vulnerable population at high risk of working memory impairments. We aimed to examine changes in the brain structural connectivity networks thought to underlie working memory performance, after completion of a working memory training program (Cogmed) compared with a placebo program in EP/ELBW children. This was a double-blind, placebo-controlled randomized trial (the Improving Memory in a Preterm Randomised Intervention Trial). Children born EP/ELBW received either the Cogmed or placebo program at 7 years of age (n = 91). A subset of children had magnetic resonance imaging of the brain immediately pre- and 2 weeks post-training (Cogmed n = 28; placebo n = 27). T₁ -weighted and diffusion-weighted images were used to perform graph theoretical analysis of structural connectivity networks. Changes from pre-training to post-training in structural connectivity metrics were generally similar between randomized groups. There was little evidence that changes in structural connectivity metrics were related to changes in working memory performance from pre- to post-training. Overall, our results provide little evidence that the Cogmed working memory training program has training-specific effects on structural connectivity networks in EP/ELBW children.

Working memory training and brain structure and function in extremely preterm or extremely low birth weight children

This study in children born extremely preterm (EP; <28 weeks' gestational age) or extremely low birth weight (ELBW; <1,000 g) investigated whether adaptive working memory training using Cogmed® is associated with structural and/or functional brain changes compared with a placebo program. Ninety-one EP/ELBW children were recruited at a mean (standard deviation) age of 7.8 (0.4) years. Children were randomly allocated to Cogmed or placebo (45-min sessions, 5 days a week over 5-7 weeks). A subset had usable magnetic resonance imaging (MRI) data pretraining and 2 weeks posttraining (structural, n = 48; diffusion, n = 43; task-based functional, n = 18). Statistical analyses examined whether cortical morphometry, white matter microstructure and blood oxygenation level-dependent (BOLD) signal during an n-back working memory task changed from pretraining to posttraining in the Cogmed and placebo groups separately. Interaction analyses between time point and group were then performed. There was a significant increase in neurite density in several white matter regions from pretraining to posttraining in both the Cogmed and placebo groups. BOLD signal in the posterior cingulate and precuneus cortices during the n-back task increased from pretraining to posttraining in the Cogmed but not placebo group. Evidence for group-by-time interactions for the MRI measures was weak, suggesting that brain changes generally did not differ between Cogmed and placebo groups. Overall, while some structural and functional MRI changes between the pretraining and posttraining period in EP/ELBW children were observed, there was little evidence of training-induced neuroplasticity, with changes generally identified in both groups. Trial registration Australian New Zealand Clinical Trials Registry, anzctr.org.au; ACTRN12612000124831.

Long-Term Academic Functioning Following Cogmed Working Memory Training for Children Born Extremely Preterm: A Randomized Controlled Trial

OBJECTIVE

To assess the effectiveness of Cogmed Working Memory Training compared with a placebo program in improving academic functioning 24 months post-training in extremely preterm/extremely low birth weight 7-year-olds.

STUDY DESIGN

A multicenter double-blind, placebo-controlled randomized controlled trial was conducted across all tertiary neonatal hospitals in the state of Victoria, Australia. Participants were 91 extremely preterm/extremely low birth weight 7-year-old children born in Victoria in 2005. Children were randomly assigned to either the Cogmed or placebo arm and completed the Cogmed or placebo program (20-25 sessions of 35-40 minutes duration) at home over 5-7 weeks. Academic achievement (word reading, spelling, sentence comprehension, and mathematics) was assessed 24 months post-training, as well as at 2 weeks and 12 months post-training, via standardized testing inclusive of working memory, attention, and executive behavior assessments. Data were analyzed using an intention-to-treat approach with mixed-effects modeling.

RESULTS

There was little evidence of any benefits of Cogmed on academic functioning 24 months post-training, as well as on working memory, attention, or executive behavior at any age up to 24 months post-training compared with the placebo program.

CONCLUSIONS

We currently do not recommend administration of Cogmed for early school-aged children born extremely preterm/extremely low birth weight to improve academic functioning.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry: ACTRN12612000124831.

Sleep Quality in Adolescents With Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME)

STUDY OBJECTIVES

Little is known about the type and severity of sleep disturbances in the pediatric chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) population, compared with healthy adolescents. Using a range of objective and subjective measures, the aim of this study was to investigate sleep quality, the relationship between objective and subjective measures of sleep quality, and their associations with anxiety in adolescents with CFS/ME compared with healthy controls.

METHODS

Twenty-one adolescents with CFS/ME aged 13 to 18 years (mean age 15.57 ± 1.40), and 145 healthy adolescents aged 13 to 18 years (mean age 16.2 ± 1.00) wore actigraphy watches continuously for 2 weeks to collect a number of objective sleep variables. The Pittsburgh Sleep Quality Index was used to obtain a subjective measure of sleep quality. Anxiety was measured by the Spence Children's Anxiety scale.

RESULTS

On average over the 2-week period, adolescents with CFS/ME were found to have (1) significantly longer objective sleep onset latency, time in bed, total sleep time, and a later rise time (all P < .005), and (2) significantly poorer subjective sleep quality (P < .001), compared with healthy adolescents. The CFS/ME patient group displayed higher levels of anxiety (P < .05), and in both groups, higher levels of anxiety were significantly related to poorer subjective sleep quality (P < .001).

CONCLUSIONS

This study provides objective and subjective evidence of sleep disturbance in adolescents with CFS/ME compared with healthy adolescent controls.