Cardiovascular Responses to Hypotension Following Muscle Mechanoreflex and Metaboreflex Activation with Aspirin in Older Adults

Low-dose aspirin increases the sensitivity of carotid baroreflex-heart rate (HR) control during concurrent muscle mechanoreflex and metaboreflex activation in older adults. However, the effect of low-dose aspirin on blood pressure (BP) and HR responses to acute hypotension, a known baroreflex stimulus, following concurrent muscle mechanoreflex and metaboreflex activation in older adults is unknown. Therefore, the effect of low-dose aspirin on BP and HR responses to acute hypotension following concurrent muscle mechanoreflex and metaboreflex activation in older adults was examined, with the hypothesis that aspirin would not affect these responses. Ten healthy older participants (61±2 years; 5 female/5 male) took daily low-dose aspirin (81 milligrams) or placebo for 7 days and then performed one trial during two visits. A cuff was inflated around one thigh for 7.5 minutes to cause limb circulatory occlusion (CO) and then rapidly deflated to induce acute hypotension. CO was preceded by 1.5-minute 70% maximal voluntary contraction isometric calf exercise, and a 3-minute passive calf stretch was applied during CO (muscle metaboreflex and mechanoreflex activation). Systolic BP (SBP), diastolic BP (DBP), mean arterial BP (MAP), and HR were recorded continuously. Aspirin did not affect the magnitude of SBP, DBP, MAP, or HR changes (P=0.2039, P=0.8095, P=0.4706, and P=0.9816, respectively) or the number of heartbeats involved (P=0.9088, P=0.4293, P=0.4504, and P=0.0510, respectively). There was a statistically significant correlation between the magnitude of the DBP change and the number of heartbeats involved with aspirin (r=-0.6791, P=0.0308) but not for SBP, MAP, or HR (SBP r=-0.3265, P=0.3572; MAP r=-0.4367, P=0.2070; HR r=0.6172, P=0.0573). Correlations between these variables were not statistically significant with placebo (SBP r=-0.3687, P=0.2944; DBP r=-0.4602, P=0.1808; MAP r=-0.4974, P=0.1435; and HR r=0.2909, P=0.4148). These findings suggest that low-dose aspirin changes the relationship between the magnitude of the DBP change and the number of heartbeats involved following acute hypotension in older adults. Supported by National Institutes of Health Grants P01-HL096570 and UL-TR-000127 (LI Sinoway) and American Heart Association Established Investigator Award (SD Stocker). This abstract was presented at the American Physiology Summit 2025 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.