# The fatigue spectrum in a community-based long haul COVID cohort

## TL;DR

This study examines fatigue in long haul COVID patients, finding that 21% meet criteria for chronic fatigue syndrome, while brain fog is a common but distinct symptom.

## Contribution

The study identifies a spectrum of fatigue in long haul COVID patients and highlights the distinct nature of brain fog.

## Key findings

- 21% of patients with fatigue met ME/CFS criteria, while 79% did not.
- Brain fog was common across all groups but showed distinct features.
- Fatigue severity was higher in patients with primary fatigue complaints.

## Abstract

In a Long Haul COVID referral clinic we describe the primary presentations of fatigue according to the CDC 2015 criteria for myalgic encephalitis/chronic fatigue syndrome (ME/CFS).

Between September 2021 and April 2022, 277 patients (61% women, 54 yrs: range 18–90 yrs) presented an average of 10 months after an acute COVID-19 infection (22% hospitalized). The clinical data were analyzed to conpare those with or without a primary or co-primary complaint of fatigue, subdivided as meeting ME/CFS criteria or not.

209 (73.5%) people (64% women) presented with fatigue. The Fatigue Severity Score was 5.33 (out 7) in those with 5.31 (SD1.54) vs. without 4.43 (SD1.65) a primary fatigue complaint (p > 0.001). Anxiety (58% vs. 38%, p < 0.02) and any psychiatric diagnosis (66% vs. 44%%, p < 0.01), but not depression itself, were overrepresented in those with Fatigue and ME/CFS. Those with prior managed sleep conditions did not increase risk for fatigue presentation. Of those with fatigue and an elevated FSS, 45/209 (21.9%) met criteria for ME/CFS. In those not meeting these criteria, associated ME/CFS symptoms were less consistent. Physical functioning by ECOG (1.88 (0.78) and 26% >2) did correlate with fatigue status. Depression was present (PHQ9 12.34 (5.95) with 63% >10) to a moderate or higher degree and was different with fatigue complaints. Brain fog (51.9%) was similar among the three categories, and correlated with FSS > 4, ECOG, and depression.

The fatigue phenotype in those presenting with it as a primary complaint comprises 21% meeting ME/CFS criteria and 79% which do not. In all the Long Haul COVID presentations. brain fog had separate, distinguishing features. Post-COVID fatigue is a spectrum which will confound clinical trials.

The online version contains supplementary material available at 10.1007/s11325-025-03512-y.