Exercise Tolerance Testing in a Prospective Cohort of Adolescents with Chronic Fatigue Syndrome and Recovered Controls following Infectious Mononucleosis

Background: Chronic fatigue syndrome (CFS) is a complex and controversial condition responsible for marked functional impairment. We recently reported that six months following acute infectious mononucleosis (IM), 13%, of adolescents met criteria for CFS. Objective: To measure exercise tolerance in adolescents with CFS and controls 6 months following IM. Design/Methods: 21 adolescents diagnosed with CFS 6 months following IM and 24 controls who had completely recovered from IM 6 months prior performed a maximal incremental exercise tolerance test with breath by breath gas analysis. Salivary cortisol was measured before and after exercise. All values are expressed as mean + standard deviation. Results: The CFS-diagnosed adolescents and controls did not differ significantly in age, weight or body-mass index (BMI). Lower VO2 peak percent of predicted was seen in adolescents with CFS following IM compared with controls (CFS 99.3 + 16.6 vs control 110.7 + 19.9, p = 0.05). Peak oxygen pulse was also significantly lower in adolescents with CFS as compared with the recovered controls (CFS 12.4 + 2.9 vs Controls 14.9 + 4.3, p = 0.03). The lower VO2 and peak oxygen pulse suggest a lower degree of fitness and a decreased efficiency of exercise, respectively, in adolescents with CFS compared to controls. A trend towards a greater rise in salivary cortisol levels in response to exercise was also seen in controls compared with cases. Conclusions: Adolescents who meet the criteria for CFS 6 months following IM have a lower degree of fitness (VO2) and efficiency of exercise (peak oxygen pulse) than recovered adolescents. Whether these abnormal exercise findings are a cause or effect of CFS or whether they can be used to determine objectively which adolescents following IM will develop CFS remains to be determined. Nevertheless, our data demonstrate that IM produces both fatigue and measurable changes in exercise testing in a subset of adolescents.