Applying Cluster Analysis to Define a Typology of Chronic Fatigue Syndrome in a Medically-Evaluated, Random Community Sample

This study involved a randomly selected, medically-evaluated, community-based sample of 166 individuals with chronic fatigue. Participants diagnosed with chronic fatigue syndrome and medically-explained chronic fatigue reported significantly more severe fatigue following exertion than the idiopathic chronic fatigue group, and participants with medically-explained chronic fatigue also reported significantly more severe fatigue following exertion than the psychiatrically-explained chronic fatigue group. A cluster analysis was performed to define a typology of chronic fatigue symptomatology for participants diagnosed with chronic fatigue syndrome. Three clusters emerged. Cluster 1 contained only one participant with chronic fatigue syndrome and was characterized by relatively low post-exertional fatigue. Cluster 2 contained a small proportion of individuals with chronic fatigue syndrome and was characterized by most severe post-exertional fatigue and most improvement in fatigue following rest. Cluster 3 contained the highest proportion of individuals with chronic fatigue syndrome, and was characterized by high post-exertional fatigue and fatigue not alleviated by rest.