Nisenbaum, R, Reyes, M, Mawle, A C et al. · American journal of epidemiology · 1998 · DOI
Researchers surveyed over 1,500 people to understand how severe fatigue and related symptoms cluster together. They found that when fatigue lasts 6 months or longer, it tends to occur alongside three groups of symptoms: mood and thinking problems, flu-like symptoms, and vision problems. This pattern of symptoms matches what doctors use to diagnose ME/CFS, suggesting these conditions share common features.
This study provides statistical evidence that ME/CFS symptoms naturally cluster into distinct groups, validating that the condition involves more than fatigue alone. Understanding these symptom patterns helps researchers and clinicians recognize ME/CFS more reliably and may guide future diagnostic and treatment approaches.
This study does not prove that these symptom clusters cause ME/CFS or explain its underlying mechanism. Being cross-sectional, it cannot establish whether symptoms develop together or in sequence, and the use of self-reported symptoms assessed over one month does not definitively identify cases meeting the 6-month CFS diagnostic criterion.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Nisenbaum, R, Reyes, M, Mawle, A C, & Reeves, W C (1998). Factor analysis of unexplained severe fatigue and interrelated symptoms: overlap with criteria for chronic fatigue syndrome.. American journal of epidemiology. https://doi.org/10.1093/oxfordjournals.aje.a009562
BibTeX
@article{mecfsatlas-nisenbaum-1998-factor-analysis,
author = {Nisenbaum, R and Reyes, M and Mawle, A C and Reeves, W C},
title = {Factor analysis of unexplained severe fatigue and interrelated symptoms: overlap with criteria for chronic fatigue syndrome.},
journal = {American journal of epidemiology},
year = {1998},
doi = {10.1093/oxfordjournals.aje.a009562},
note = {PubMed: 9663406},
url = {https://www.mecfsatlas.com/evidence/nisenbaum-1998-factor-analysis},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-25. https://www.mecfsatlas.com/evidence/nisenbaum-1998-factor-analysis
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