Mild versus severe fatigue in polio survivors: special characteristics

In studies conducted on polio survivors with late effects of poliomyelitis, new fatigue is frequently reported. The main purpose of the present study was to examine the characteristics of polio survivors reporting severe fatigue versus those reporting mild or no fatigue. From a survey among 276 representative Norwegian polio survivors, we recruited all patients with mild/no fatigue and those with severe fatigue, without other diseases than poliomyelitis. Out of 276 polio survivors, 43 reported mild, 113 moderate and 118 severe fatigue (2 were missing). Only 12 with mild fatigue, 21 with moderate and 14 with severe fatigue had no other diseases and health problems related to fatigue. Six of these patients with mild/no and 9 with severe fatigue, and 16 healthy persons participated in the study. The subjects were assessed with the Fatigue Questionnaire, Fatigue Severity Scale, Visual Analog Scale for pain and fatigue, SCL-90-R, cognitive tests, event-related brain potentials (ERPs), blood and urine parameters, spirometry, exercise and muscle strength tests, 24-hour pulse registration, Sunnaas ADL-index and the Rivermead Mobility Index. The group with severe fatigue had significantly more elevated scores on SCL-90-R, measuring obsessive-compulsive behaviour, depression and anxiety than both the mild fatigue group and the controls. They also had higher scores on the somatization scale than the control group. No other test results showed significant differences between the mild/no and the severe fatigue polio groups. The present results give no support to the hypothesis of "brain fatigue in polio survivors, assessed by cognitive tests or ERPs. Moreover, the physical test results did not correspond to perceived fatigue. Thus, the only characteristics distinguishing polio survivors with severe fatigue from those with mild/no fatigue in this study were psychological characteristics. However, a larger group of polio survivors suffer from additional diseases, and such diseases should be ruled out during a comprehensive rehabilitation program.