Association between standing blood pressure and autonomic dysfunction in orthostatic hypertension

Background: Orthostatic hypertension (OHT), characterized by a significant increase in systolic blood pressure (SBP) upon standing, has been recognized as a risk factor for adverse cardiovascular events, likely linked to autonomic dysfunction. However, it remains unclear whether the SBP rise (∆SBP) itself, independent of the absolute level of standing SBP, reflects autonomic dysfunction. Therefore, this study aimed to compare autonomic function among individuals with marked orthostatic SBP rise with or without a high standing SBP, as well as healthy controls and those with resting hypertension (HT). Hypothesis: We hypothesized that autonomic dysfunction would be present only in individuals with a high standing SBP among those exhibiting an orthostatic SBP rise. Methods: We recruited 135 individuals (age, 41 ± 15 years) without known cardiovascular diseases, although some participants had hypertension. Participants underwent a 10-minute supine rest followed by10-minute active standing test with continuous beat-by-beat and heart rate recording. Heart rate variability (HRV), SBP variability (BPV), and spontaneous cardiovagal baroreflex sensitivity (CBRS, sequence method) were calculated during 5 minutes of supine rest and from 3 to 8 minutes after standing. Participants were classified into 4 groups based on their ∆SBP and SBP measured with an upper-arm cuff, as following: 1) Control (N = 73): 10 >∆SBP > -5mmHg and standing SBP < 130 mmHg, 2) Pseudo-OHT (p-OHT) (N = 28): ∆SBP ≥ 10 mmHg and standing SBP < 130 mmHg, 3) OHT (N = 9): ∆SBP ≥ 10 mmHg, supine SBP < 130mmHg, and standing SBP ≥ 130 mmHg, and 4) supine HT (N = 12): 10 >∆SBP > -5mmHg and supine SBP ≥ 130 mmHg. Results: Supine parasympathetic HRV parameters (SDNN, RMSSD, and pRR50) and supine CBRS (control, 17.8 ± 8.6; p-OHT, 17.9 ± 8.4; OHT, 7.4 ± 2.1; HT, 9.5 ± 4.8 msec/mmHg) in OHT and HT groups were significantly lower than those in the other groups (all P < 0.05 in one-way ANOVA with Tukey post-hoc test), and these differences persisted during standing. There were no significant differences in HRV or CBRS between HT and OHT groups. The RMSSD and HF of BPV were significantly higher in HT group than in the other groups (P < 0.05). The BPV parameters in OHT group did not differ from Control or p-OHT group in either supine or standing positions (P > 0.05). No significant differences were observed in HRV, BPV, or CBRS between Control and p-OHT groups. Discussion and Conclusion: While it is well established that autonomic function is impaired in hypertension, the present results demonstrate that subjects with a marked orthostatic increase in SBP and a standing SBP ≥ 130 mmHg exhibited resting autonomic function comparable to that of subjects with hypertension, despite having normal supine SBP. In contrast, impaired autonomic function was not observed in subjects with a standing SBP < 130 mmHg, even if they showed an orthostatic SBP rise. These observations indicate that both the orthostatic increase in BP and the absolute level of standing SBP are important determinants of autonomic impairment. These findings suggest that assessing standing BP, in addition to resting BP, may help identify concealed autonomic dysfunction. Funding Information: NIH R01 HL144781 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.