The effect of seasonal temperature changes on heart rate variability in healthy elderly

• Main Authors: Po-Chun Huang, 黃柏鈞
• Other Authors: Chin-Sheng Tang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/4czrmv

碩士 === 輔仁大學 === 公共衛生學系碩士班 === 101 === Purpose Climate changes and global warming have enormous effects on environment and human life. Many epidemiological studies show that temperature and air pollutants have adverse effects on alternate cardiac autonomic function. Heart rate variability (HRV) is a non-invasive assessment method for cardiac autonomic nervous system and has been an important indicator to explore cardiovascular disease morbidity and mortality. The purpose of our study is to investigate the influence of subtropical climate extremes on HRV parameters in healthy elders, and to assess different environmental indicators appropriate to evaluate the effects of temperature-humidity changes on HRV parameters in healthy elders. Methods We recruited seven healthy elders aged from 57-83 years, and used direct reading instrument and portable electrocardiogram (ECG) recorder to measure continuous 72 hours real-time data of the ECG, ambient temperature and relative humidity, and air pollution exposures in summer and winter. Generalized additive mixed model (GAMM) was used to explore the association between environmental temperature-humidity and HRVs by controlling air pollutants and other potential confounding factors. The environmental temperature-humidity indicators evaluated in our study included air temperature, wet bulb globe temperature (WBGT), humidex and heat index. Results The results of our study showed that the subjects’ HRV parameter values in winter is higher than that in summer mostly. Nonlinear relationships between environmental temperature-humidity indicators and HRV parameters in both summer and winter were found by GAMM analysis. When we stratified the data by different seasons, the WBGT indicator and most HRV parameters were linearly positive associated or showed the zero slope in summer, while the WBGT indicator and most HRV parameters were linearly inverse associated in winter. Summarized the differences of explanatory power , Akaike information criterion, and Bayesian Information Criterion in various environmental temperature-humidity indicators assessment models, we found WBGT was the most suitable temperature-humidity environment indicator to assess HRV parameters variation. In multi-pollutant models, as WBGT rised 1℃ in winter, the r-MSSD, SDNN, pNN50+1, TP, and LF/HF of subjects significantly reduced 9.814%, 5.382%, 17.312%, 9.823%, and increased 6.993%, respectively. The LF/HF significantly reduced 6.551%, but SDNN and HF of subjects significantly increase 2.997%, and 13.202% in summer. While in summer when WBGT rised, the r-MSSD, pNN50+1, LF, TP and HR of subjects all showed an increase trend, but was not statistically significant. Conclusion We found nonlinear relationships between the HRV parameters of healthy elders and temperature-humidity environment. The WBGT was more suitable than other environmental temperature-humidity indicators for assessing the effects of subtropical temperature-humidity changes on the HRVs of healthy elders, and rised WBGT caused HRV parameters to change significantly in different seasons.