Long COVID versus FM/CFS/ME: overlap and differences in patient-reported burden

Background

Long COVID shares prominent symptoms with fibromyalgia/chronic fatigue syndrome/myalgic encephalomyelitis (FM/CFS/ME), but the extent of overlap and separation in patient-reported and functional burden is still unclear. We compared both groups against recovered controls.

Methods

We performed a cross-sectional analysis of the ARALONGCOV database in Aragon, Spain, including long COVID cases, FM/CFS/ME participants and recovered controls. We compared SF-12, Fatigue Severity Scale (FSS), Pittsburgh Sleep Quality Index (PSQI), PHQ-9 and 6-minute walk distance using available data in each domain.

Results

Both long COVID and FM/CFS/ME showed substantially worse outcomes than controls. Median SF-12 scores were 32.1 in long COVID, 20.4 in FM/CFS/ME and 87.5 in controls. Median FSS scores were 57, 61 and 6, respectively; median PSQI scores were 12, 14 and 6; median PHQ-9 scores were 12, 15 and 1; and median 6-minute walk distances were 440 m, 418 m and 541.5 m. Global between-group differences were highly significant across all domains (all p < 0.001). Compared directly with long COVID, FM/CFS/ME participants showed poorer quality of life, higher fatigue, poorer sleep, more depressive symptoms and lower exercise capacity, although both groups were markedly more impaired than controls.

Conclusions

Long COVID and FM/CFS/ME showed overlapping multidimensional burden, with FM/CFS/ME generally more severely affected. These findings support a comparative framework for studying shared and distinct mechanisms, while highlighting the substantial functional impact of long COVID in primary care.

Key messages

• Long COVID and FM/CFS/ME showed marked overlap in multidimensional burden, with both groups far more impaired than controls.

• FM/CFS/ME was generally more severely affected, supporting comparative research on shared and distinct mechanisms.