空氣污染對冠狀動脈心臟病病人心跳回復率及心律變異性的影響

Abstract

過去研究證實短期及長期的空氣污染暴露會導致不良健康效應增加，特別是在呼吸道與心血管疾病方面，而心血管疾病則為台灣人們近代死亡原因的主因之一。已知空氣污染會透過影響心臟自律神經功能的調控，而增加心血管疾病發生率及死亡率的風險，文獻顯示心跳回復率（Heart Rate Recovery, HRR）與心率變異性（Heart Rate Variability, HRV）均可作為自律神經功能的健康指標，然而過去研究多探討空氣污染對心律變異性的影響，而未有空氣污染與心跳恢復率關係之研究，因此本研究欲探討空氣污染對冠心病病人心跳恢復率及心律變異性之效應。 我們收集台灣嘉義地區57位冠心病病人，每三個月追蹤一次，共四次無徵狀跑步機運動測試（Symptom-limited Exercise Treadmill Test）及心電圖測試資料，每分鐘心跳恢復率定義為受試者運動期間最大心跳數減掉運動過後每分鐘心跳數之差值。根據環保署空氣品質監測站之數據，分別計算嘉義鄰近測站主要空氣污染物（CO、NO2、SO2、O3、PM10和PM2.5）以及溫濕度的每日平均值，並利用1至5天的移動平均值(Moving-average)及1至5天的單日延遲（Single-lag）平均濃度作為不同暴露情形的評估。本研究以混合效應統計模式（Mixed Effects Model)來評估空氣污染物對冠心病病人心跳恢復率及心律變異性的效應，並進一步加入第二種空氣污染物來探討不同空氣污染物間造成的干擾及其效應（Two Pollutants Model）。 研究結果顯示每增加一個四分位差之二氧化硫濃度的暴露會使得第一到第六分鐘的心跳回復率顯著下降，且具有累積效應及延遲效應，即便控制臭氧的影響，效應仍存在第一分鐘心跳回復率，而懸浮微粒（PM10）濃度的暴露增加亦會使前兩分鐘的心跳回復率顯著下降。大氣微粒（PM10和PM2.5）在暖季對心跳回復率的影響較冷季來得大，依據不同風向對第一分鐘心跳回復率的影響推測，PM10的主要來源為測站西北方。 另一方面，以頻域分析法得到的心率變異性對空氣污染較敏感，每增加一個四分位差之二氧化硫濃度和細懸浮微粒（PM2.5）濃度暴露會使得心律變異性顯著改變，且具有較顯著的微粒效應，即便控制臭氧的影響，PM10和PM2.5在LF的部分仍呈現顯著的累積效應。二氧化硫和PM10在暖季對HF指標影響較冷季大，而PM10和PM2.5在冷季對於LF/HF指標的影響則較暖季顯著，依據不同風向對心率變異性指標的影響推測，PM2.5的來源為自測站西南方的較西北方多。 過去研究顯示心跳回復率減少、心率變異性下降皆會顯著增加心血管疾病的發生與死亡風險，由本研究可以得知，PM10和PM2.5對代表心臟自律神經功能指標的心跳恢復率及心律變異性有其效應，會使其顯著下降，而心跳恢復率及心律變異性兩者對交感、副交感活性的代表程度卻不盡相同。頻域分析法較時域分析法適合用來做為探討空氣污染對心率變異性健康指標影響的方法，而空氣污染會使得交感、副交感神經系統平衡趨向副交感神經的抑制，因此心跳回復率可做為探討空氣污染對自律神經功能調控的良好指標。探討空氣污染造成的健康效應會受到糖尿病、高血壓和高血脂等共病現象以及β-blocker、Calcium Channel Blocker、Statin、ACE Inhibitor或ARB藥物的使用所調控，而其機轉則有待進一步的研究分析。

Previous studies had shown that air pollution exposure may cause short-term and long-term health effects, especially on respiratory and cardiovascular disease. Cardiovascular disease has been the leading cause of death in Taiwan. It is known that air pollution may influence the sympathovagal regulations, and increase the risk of cardiovascular disease morbidity and mortality. Heart rate recovery (HRR) and heart rate variability (HRV) have been used as a heath indicator of autonomic function. However, most air pollution studies have been focused on HRV. The effects of air pollution on HRR haven’t been investigated. Thus, in this study we studied the effects of air pollutants on HRR in patients with coronary artery disease (CAD). This study recruited 57 CAD patients based on symptom-limited exercise treadmill test and electrocardiogram at Chia-Yi area in Taiwan between December 2005 and March 2007. Each patient was examined once every three months for totally 4 times. HRR was defined as the difference between the peak heart rate during the exercise and the recovery heart rate after the exercise. CO, NO2, SO2, O3, PM10 , PM2.5, temperature and humidity data recorded by 6 air monitoring stations from EPA were gathered and daily averages were calaulated. We used mixed effect model to determine the effects of air pollution on both HRR and HRV in CAD patients. Furthermore, we used two-pollutant models to estimate the effects using both single-lag model and moving-average model from day 1 to day 5. The trend of both accumulative and single-lag effect of SO2 exposure was significantly associated with decreased HRR from first to sixth minute. Besides, the associations of SO2 were even substantially increased after O3 was controlled in both moving-average models and single-lag models. The associations between particulate matters (PM10 and PM2.5) and HRR were significant in warm season. According to the influence of different directions of wind on HRR, PM10 mainly come from northwest. On the other hand, particulate effect had been shown in frequency domain HRV parameters and the associations of PM10 and PM2.5 were still significant after O3 was controlled in LF. Based on the effects of different directions of wind on HRV, PM2.5 come from southwest more than northwest. Previous studies have shown that decreased HRR and HRV were significantly associated with cardiovascular morbidity and mortality. This study reveals an association between particles (PM10 and PM2.5) and decreased HRR as well as HRV in patients with coronary artery disease. Nevertheless, the representation on the sympathovegal activity of the two health indicators are different. It is better to use the frequency domain HRV parameters to evaluate the effects of air pollution than to use time domain HRV parameters. Patients with comorbidity and medication use may modify the effects of autonomic dysfunction by air pollution exposure. The adverse health effects of air pollution may be modified by patients with diabetes, hypertension or hyperlipidemia comorbidity, and β-blocker, calcium channel blocker, statin, angiotensin converting enzyme inhibitor or angiotensin receptor blocker medication use. Because the balance of autonomic nervous system may be toward parasympathetic nerve suppression, heart rate recovery could be used as a good index for investigating the interference of air pollutant on autonomic nervous system function, while its mechanism requires further study and analysis.