Effects of cold ambient temperature on morning blood pressure surge and autonomic nervous system function during late sleep stage transition in humans

• Main Authors: Cian-Hui Hong, 洪千慧
• Other Authors: Cheryl C.H. Yang
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/12513446342746484834

碩士 === 國立陽明大學 === 腦科學研究所 === 100 === Background: Several lines of studies have demonstrated a link between the occurrence of cardiovascular events and low ambient temperature as well as morning blood pressure surge (MBPS). Neuronal control of the cardiovascular system, a possible etiology, also dramatically changes in association with these sleep structure changes. The ambient temperature of winter in Taiwan is around 10-20 °C, a warmer condition relative to other countries, but the cardiovascular disease events also occur more frequently in winter than the other seasons. However, the relationship between ambient temperature and autonomic function in late sleep stages with MBPS has not been thoroughly investigated. We purposed that cold ambient temperature should produce a higher sympathetic activity and sympathetic change during late sleep and sleep transition, respectively. We also purposed cold ambient temperature might be a critical role in cold-related MBPS. Methods and Results: All experiments were carried out on 10 healthy male adults, aged 23.80  0.87. Subjects should be normotansive, with body mass index (BMI) between 18 and 24 and without taking medication, drinking and smoking. All participants participated in 2 experimental conditions randomly, a warm condition (23℃) and a cold condition (16℃), with intervals of more than one day between conditions. BP was measured every 30 minutes for 24 hours by an autonomic ambulatory BP monitor. The electroencephalogram (EEG), electrocardiogram (ECG) and temperature were recorded with a miniature polysomnography for 24 hours. Subjects wore the same clothes we provide and filled out visual-analogue scales for subjective feelings about the condition. The EEG and ECG signals were used for sleep scoring and heart rate variability (HRV) and processed by frequency analysis. We found that in cold condition, (1) the magnitude of MBPS was greater than in warm condition. (2) a significant and great sympathetic index (normalized low frequency power of HRV, LF%) changes were found in sleep-wake transition than the changes of cover-uncover and supine-sit position. (3) the baseline sympathetic activity and the NREM-REM transition-related sympathetic elevation were significant higher in the late sleep period than in the early sleep period in cold condition. And the vagal index (high frequency power of HRV, HF) revealed almost contradict responses. (4) The arousal index was trended higher than in the warm condition. (5) a value of sleep-wake transition related RR and total power of HRV changes were significantly correlated with the value of MBPS. Conclusions: Cold ambient temperature may be an important determinant for MBPS, autonomic function in late sleep stage transition and sleep architecture. Cold ambient temperature can elevated the amplitude of MBPS and also be associated with sympathetic activation during late sleep stage transition. It should be an important implication for cold related cardiovascular events occurring.