Quantifying The Symptom Burden Of Acute Exercise In Gulf War Illness

Post-exertional malaise is described as symptom worsening following physical or mental exertion and is considered a characteristic of Gulf War Illness (GWI). Experimentally, this phenomenon has been difficult to quantify due to high variability in symptom profiles across Veterans with GWI. Hence, we developed a metric to better represent post-exercise symptom responses. PURPOSE: To test an integral-based method that captures three key components: (1) symptom severity, (2) symptom time course, and (3) symptom changes pre- to post-exercise. METHODS: Veterans with GWI (N = 35) and healthy Veteran controls (N = 28) performed 30 minutes of cycling exercise (70% ± 5% heart rate reserve). Symptoms were measured for three days pre- and post-exercise using 0-100 visual analogue scales (VAS) operationalized from the GWI Kansas case definition. An area under the curve (AUC) was calculated using mathematical integrals of VAS responses for pre- and post-exercise periods. Symptom scores for fatigue, neurocognitive/mood, and pain domains were calculated as a ratio of the change in AUC from pre- to post-exercise multiplied by the post-exercise AUC. Spearman correlations were calculated between symptom scores and validated measures of fatigue (Brief Fatigue Inventory; BFI), mood (Profile of Mood States; POMS), and pain (Short-Form McGill Pain Questionnaire 2; SF-MPQ-2). RESULTS: Fatigue-related symptom scores were significantly (p < 0.05) correlated with BFI scores at 24, 48 and 72 hours post-exercise (rs = 0.67 - 0.73) as well as POMS fatigue subscale scores 24 hours post-exercise (rs = 0.58). Neurocognitive/mood-related symptom scores were significantly correlated with 24 hour post-exercise POMS total mood disturbance (rs = 0.5). Pain-related symptom scores were significantly correlated with total SF-MPQ-2 scores at 24 hours post-exercise (rs = 0.54). CONCLUSIONS:The proposed symptom score is a suitable representation of the symptom burden experienced by Veterans with GWI following acute exercise. Future research will aim to further validate this measure and explore associations with biological outcomes. Supported by a grant from the U.S. Department of Veterans Affairs #I01 CX001329 Supported by a grant from the U.S. Department of Veterans Affairs #I01 CX001329