Aim: Few studies on water intake, autonomic nervous activity and factors affecting autonomic nervous activity have been conducted on older adults. In this study, autonomic nerve activity after ingestion of water in older adults was investigated by heart rate variability analysis, and the purpose was to analyze and examine the influence of body composition
and lifestyle habits.
Methods: Thirty-eight older adults (male: 11, female: 27, mean age: 74.2 years) were surveyed regarding their lifestyle (movement, chronic disease, medication, drinking, sleep state) and measurements were taken of their body compositions (height, weight, body fat mass, body muscle mass). In addition, we measured heart rate variability before and immediately after water intake in all subjects. For heart rate variability components, total power (TP), very low frequency (VLF), low frequency (LF), high frequency (HF), low frequency power in normalized units (LF Norm), high frequency power in normalized units (HF Norm), and low-to-high frequency ratio (LF/HF) were used for analysis.
Results: Before water intake, heart rate had a tendency to increase in the older adults with insufficient sleep. There was a significant decrease among those who took medication in their heart rate variability analysis components TP, LF, HF before water intake (P＜0.01). Immediately after water intake, a significant relationship was observed between heart rate variability analysis components TP, VLF, LF, LF/HF and subjects＇ sleeping conditions, medication, or body weight. In addition, a significant relationship was observed between body weight and LF Norm, HF Norm after water intake (P＜0.01). In terms of body weight, body fat mass and muscle mass were shown to be related to LF Norm and HF Norm. There was no significant difference in heart rate change and heart rate variability analysis components before and after water intake, but significant interactions in TP and HF changes before and after water intake were observed in those with routinely frequent movement (TP: P＜0.05, HF: P＜0.001). LF Norm and HF Norm change before and after water intake showed a weak interaction with drinking frequency and body weight (P＜0.05).
Conclusion: Heart rate variability before and after water intake in older adults was influenced by various factors.Medication, sleep state, body composition as well as drinking and movement habits may be related to heart rate variability in older adults. It is necessary to investigate these factors further to obtain more information. It is important to understand autonomic nervous activity and the factors that influence older adults＇ heart rate variability analysis in detail to prevent various disorders of older adults so that they can maintain their health.