Gulf War Illness (GWI) is a multisystem disease affecting ~30% of the Veterans who served in the 1990-1991 Gulf War. Symptoms of GWI include chronic pain, fatigue, mood disturbances, and cognitive complaints, which suggest a neurological origin. Cerebrovascular regulation is closely linked with neurological health; however, it remains unclear whether Veterans with GWI (GWI+) have impaired cerebrovascular regulation, especially in response to physiological stressors. Thus, the purpose of this study was to investigate differences in cerebrovascular and cardiovascular responses to a physiological stressor (i.e., an isometric handgrip exercise; IHG) between GWI+ and deployment-matched Veterans without GWI (GWI-). We hypothesized that GWI+ Veterans would have impaired cerebrovascular and cardiovascular responses to IHG when compared to GWI- Veterans. Thirty-nine Gulf War Veterans (age = 59 ± 4 years; 34M/5F) were included in this study and categorized as (GWI+: n = 23, GWI-; n = 16). After a brief period of supine rest, baseline variables were recorded for 3 minutes followed by the IHG protocol involving exercise at 40% of their maximum voluntary contraction (MVC) until failure. Continuous measures of heart rate (HR) via 3-lead ECG, mean arterial pressure (MAP) via finger plethysmography, and middle cerebral artery blood velocity (MCAv) via transcranial Doppler ultrasound were obtained throughout the protocol. Cerebrovascular resistance index (CVRi) was calculated as MAP/MCAv. IHG duration was divided into tertiles for analysis. Independent T-Tests were used to compare differences in the percent change between baseline and IHG. There were no differences between groups at baseline for MAP (GWI-: 101 ± 10 mmHg, GWI+: 103 ± 14 mmHg; p = 0.635), HR (GWI-: 64 ± 11bpm, GWI+: 62 ± 9 bpm; p = 0.646), MCAv (GWI-: 50 ± 10 cm/s, GWI+: 50 ± 9 cm/s; p = 0.907), and CVRi (GWI-: 2.10 ± 0.54 mmHg/cm/s, GWI+: 2.15 ± 0.51 mmHg/cm/s; p = 0.771). During the final tertile of IHG, when the sympatho-excitatory stimulus was highest, there were no group differences in the IHG response for MAP (GWI-: 23 ± 12%, GWI+: 24 ± 13%; p = 0.917), HR (GWI-: 26 ± 14%, GWI+: 27 ± 17%; p = 0.776), or MCAv (GWI-: 7 ± 15%, GWI+: 13 ± 9%; p = 0.152). However, GWI+ had a smaller increase in CVRi in response to IHG (GWI-: 17 ± 15%, GWI+: 7 ± 11%, p < 0.050). These findings suggest that Veterans with GWI had attenuated cerebral vasoconstriction during a hypertensive stimulus, despite similar cardiovascular responses, compared with Veterans without GWI. This indicates that GWI+ Veterans may have altered cerebrovascular regulation in response to physiological stressors. Future work should investigate whether these differences in cerebrovascular regulation contribute to GWI symptomology. Funding Resource: Department of Defense W81XWH1910381 and National Institutes of Health T32HL007936 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Steplyk et al. (Fri,) studied this question.