Parasympathetic Nervous Activity Associated with Discoordination Between Physical Acceleration and Heart Rate Variability in Patients with Sleep Apnea.

Sleep apnea syndrome (SAS) often accompanies alterations in heart rate variability (HRV). The severity of SAS is sometimes evaluated using the oxygen desaturation index (ODI). We hypothesized that effects of the autonomic nervous system could be involved in the coordination between HRV and physical acceleration during free movement in patients with SAS. Among 33 women aged 60 years or older, 19 had a high ODI (>5). Their HRV and physical acceleration were simultaneously obtained every minute for 24 hours. The low frequency/high frequency (LF/HF) ratio and the high frequency in normalized units (HFnu) were used as HRV indices. Low levels of %Lag0, defined as the percentage of the lag = 0 min in 1 h, indicated coordination between physical acceleration and HRV. Nineteen participants were divided into group A (high %Lag0 before sleep [n = 9]) or group B (low %Lag0 [n = 10]). In group B participants with a high ODI and low %Lag0 in the hour after waking, HFnu was significantly increased compared to that in group A participants with high ODI and high %Lag0 in the hour after waking (p < 0.05). These results suggest that close associations between high ODI and discoordination between HRV and physical acceleration may be due to higher parasympathetic nervous system activity after waking.

Coordination between heart rate variability and physical activity may be diminished by fatigability in non-older women in the hour before sleep.

Fatigability is related to several diseases as well as the autonomic nervous system. We investigated whether fatigability is associated with coordination between physical acceleration (PA) and parasympathetic nervous activity (PSNA) in women. Overall, 95 women were divided into non-old (n = 50; age: 22-59 years) and old (n = 45; age: ≥60 years) groups. PSNA and PA data were simultaneously obtained every minute for 24 h. We defined %lag0 as the percent ratio of lag = 0 min between PSNA and PA in 1 h. Cornell Medical Index was used to determine the degrees of physical and psychological symptoms. In the non-older group in the hour before sleep, the participants with high fatigability scores had significantly lower %lag0 than those with low fatigability (p < 0.05). Additionally, those with higher fatigability combined with exhaustion in the morning had significantly lower %lag0 than those without exhaustion in the hour before sleep (p < 0.05) but not in the hour after waking up. These results suggest that fatigability in non-older women was associated with loss of coordination between PSNA and PA in the hour before sleep. Additionally, exhaustion in the morning may be related to loss coordination of PSNA and PA during the previous night.