Key result
Higher habitual waking lying time, but not sitting, is linked to lower vagally-mediated HRV.
Why the study?
Heart rate variability is an established marker of autonomic cardiac control, but whether time spent sitting versus lying influences vagal outcomes remains to be determined.
Does habitual lying time reduce vagal-related heart rate variability outcomes in healthy young adults?
Cross-Sectional (n=31)
No
Does habitual lying time reduce vagal-related heart rate variability outcomes in healthy young adults?
More habitual waking time spent lying, but not sitting or total sedentary time, is paradoxically associated with worse vagally-mediated cardiac control in healthy young adults.
Answers are grounded in this paper and cite their sources.
Lying time was associated with lower vagal HRV in young adults; hypothesis-generating and requires prospective confirmation.
Heart rate variability (HRV) is a well-established noninvasive marker of autonomic cardiac control. We test whether time spent sitting (negatively) versus lying (positively) influences vagal HRV outcomes. HRV (10 min supine electrocardiogram) and free-living postures (dual-accelerometer configuration, 7 days) were measured in 31 young healthy adults (15♀, age: 23 ± 3 years). Habitual lying (66 ± 61 min/day), but not sitting time (558 ± 109 min/day), total sedentary time (623 ± 132 min/day), nor step counts (10 752 ± 3200 steps/day; all, p > 0.090), was associated with root mean square of successive cardiac interval differences (ρ = −0.409, p = 0.022) and normalized high-frequency HRV (ρ = −0.361, p = 0.046). These findings document a paradoxical negative impact of waking lying time on cardioautonomic function. Take home message Using a multi-accelerometer configuration, we demonstrated that more habitual waking time lying, but not sitting or total sedentary time, was associated with worse vagally mediated cardiac control.
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O’Brien et al. (2023) conducted a cross-sectional in Healthy young adults (n=31). Habitual lying time vs. Habitual sitting time or total sedentary time was evaluated on Correlation between total lying time and root mean square of successive cardiac interval differences (RMSSD) (ρ=-0.409, p=0.022). Higher habitual waking lying time, but not sitting or total sedentary time, was inversely associated with vagally-mediated cardiac control, including RMSSD and normalized HF-HRV.
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