Sex differences in blood pressure responsiveness to spontaneous K-complexes during stage II sleep

Abstract

K-complexes are a key marker of nonrapid eye movement sleep, specifically during stages II sleep. Recent evidence suggests the heart rate responses to a K-complexes may differ between men and women. The purpose of this study was to compare beat-to-beat blood pressure responses to K-complexes in men and women. We hypothesized that the pressor response following a spontaneous K-complex would be augmented in men compared with women. Ten men [age: 23 ± 2 yr, body mass index (BMI): 28 ± 4 kg/m²] and ten women (age: 23 ± 5 yr, BMI: 25 ± 4 kg/m²) were equipped with overnight finger plethysmography and standard 10-lead polysomnography. Hemodynamic responses to a spontaneous K-complex during stable stage II sleep were quantified for 10 consecutive cardiac cycles, and measurements included systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and heart rate. K-complex elicited greater pressor responses in men when blood pressures were expressed as SAP (cardiac cycle × sex: P = 0.007) and DAP (cardiac cycle × sex: P = 0.004). Heart rate trended to be different between men and women (cardiac cycle × sex: P = 0.078). These findings suggest a divergent pressor response between men and women following a spontaneous K-complex during normal stage II sleep. These findings could contribute to sex-specific differences in cardiovascular risk that exist between men and women.NEW & NOTEWORTHY K-complexes during stage II sleep have been shown to elicit acute increases in blood pressure and heart rate, but the role of sex (i.e., male vs. female) in this response is unclear. In the present study, we demonstrate that the pressor response following spontaneous K-complexes were augmented in men compared to age-matched women. The augmented blood pressure reactivity to spontaneous K-complexes during stage II sleep in men advance the field of cardiovascular sex differences, with implications for nocturnal blood pressure control.

Keywords: blood pressure; nonrapid eye movement sleep; polysomnography; pressor response.

Figure 1.

Representative recordings of 1 male and 1 female pressor response to spontaneous, isolated K-complexes during stage II sleep. The blood pressure increase was augmented in men when compared with women. An electrocardiogram (ECG), beat-to-beat blood pressure waveform, and sleep electroencephalogram (EEG) are represented for each participant.

Figure 2.

Changes in blood pressure and heart rate (HR) following spontaneous, isolated K-complexes during stage II sleep (C0) and 10 subsequent cardiac cycles (C1-C10). K-complexes increased systolic (SAP) and diastolic arterial pressure (DAP) in both men and women. The pressor response to a spontaneous K-complex was significantly higher in men when compared with women. Repeated-measures ANOVA with sex (men vs. women) as the between factor and cardiac cycle as the within factor were used to compared blood pressure and heart rate. Data depicted as means ± SD. *P < 0.05 between groups (men vs. women).