Harper, Jennifer L.

Background Repetitive hypoxic apneas, similar to what is observed in sleep apnea, result in resetting of the sympathetic baroreflex to higher blood pressures (BP) in humans. This resetting of the baroreflex is associated with increased BP in preclinical models of sleep apnea (chronic intermittent hypoxia, CIH); however, the majority of our understanding comes from men. There are data to suggest female rats exposed to CIH do not develop high BP. With this, we sought to examine potential sex‐related differences in the effect of intermittent hypoxia (IH) on the sympathetic baroreflex. We hypothesized young men would exhibit resetting of the baroreflex to higher BP following IH, with no change in young women. Methods BP and muscle sympathetic nerve activity (MSNA) were assessed in 17 men (30±1 yrs) and 10 women (28±1 yrs) during quiet normoxic rest prior to and following 30‐min of experimental IH [30‐s hypoxic exposures (0.05 F i O 2 ) alternating with 90‐s room air breathing] resulting in 15 hypoxic events (91.7±0.5 % SpO2). Sympathetic baroreflex sensitivity was evaluated using the modified Oxford technique before and after 30‐min of IH. Results Diastolic BP increased in men following IH (71±2 to 74±2 mmHg; p<0.01) with no change in women (75±3 to 75±3 mmHg; p=0.97). Sympathetic baroreflex sensitivity did not change following IH in either group (Men: −1.8±0.2 to −1.9±0.3; Women: −1.6±0.3 to −2.1± 0.5 bursts/100 heart beats/mmHg; Main effect of IH, p=0.14; Interaction of group and IH, p=0.28). Conclusion Acute IH resets the sympathetic baroreflex to higher BP in young men, with no change in young women. Baroreflex sensitivity slopes were unchanged in either group following IH. Our results support sex differences in the effect of IH on sympathetic control of BP and show that young women are protected from the BP‐raising effects of IH. These data enhance our understanding of sex‐specific mechanisms that may contribute to the development of hypertension in sleep apnea. Support or Funding Information NIH HL130339, Mayo Clinic Center for Biomedical Discovery