職業階層及十二小時輪班工作之心血管效應

Abstract

台灣過去四十年來的經濟起飛，工業的急速發展扮演了重要的角色，然而相伴而來的各種環境與職業病，卻一直被低估而忽略。由歐美各先進國家之經驗，與環境職業相關之動脈硬化疾病屢不少見，值得我們借鏡並加以防範。 以往由於管理階層之工作壓力與動脈硬化之關聯並不明確，血壓上昇的時間因素與頸動脈硬化的關係，目前仍不清楚。本研究第一部份，我們在台北市的一家石化公司的95位主管階層與91位年齡、性別配對的員工進行此研究，以瞭解時間加權平均24小時移動式收縮壓(TWA-SBP)，罹患高血壓的時間(高血壓年)，和頸動脈硬化的關係。兩側顱外頸動脈的內皮加中皮層厚度(intima-media thickness, IMT)及頸動脈硬化塊，由高顯像的B模式頸動脈超音波來測量。結果發現，部位特殊性的IMT其決定因子如下，混合迴歸模式分析發現時間加權平均24小時移動式收縮壓及高血壓年是總頸動脈及球體部IMT主要的決定因子。而時間加權平均舒張壓(TWA-DBP)是反向的決定因子，而糖尿病年則是內頸動脈及球體部IMT的決定因子。同時發現非主管階層員工在球體部的IMT較厚。在調整相關的因子後，多變項邏輯式分析發現TWA-SBP和高血壓年皆是較厚的IMT及顱外頸動脈硬化塊≥3的重要決定因子。總之，TWA-SBP和高血壓年皆是IMT及頸動脈硬化的主要決定因子，而此發現亦指出短期與長期的血壓上昇在發生頸動脈硬化上是重要的。 12小時輪班在半導體公司相當普遍，其心臟血管的建康效應，迄今並無結論。本研究的第二部份，是評估12小時輪班工作之血流動力學效應，以及在12小時輪班後，其動態的血壓及心率變異性的改變。民國91年在新竹一半導體工廠，我們邀請了15位男性平均32.9歲的輪班工人參加此研究。每位參加的工人皆接受總共48小時的連續性攜帶式血壓偵測，即輪班工作12小時及休息36小時。當中，有7位完成了總共96小時的血壓及心跳偵測，即夜間及日間各一次的48小時連續血壓偵測。這些工人我們用混合迴歸模式分析來評估12小時輪班工作，是否會延緩其血壓及心跳的正常恢復。另外夜間及日間各有6位工人在48小時連續血壓偵測時，同時完成一次48小時連續心電圖偵測。基於對等比較，我們用配對t-檢定來評估在同一時間表上(例如晚上10點工作與隔日的晚上10點休息相比)，同一位受測者兩次測量(工作與休息)間是否有顯著差異。結果發現相對於休息時間，12小時夜間輪班工作會持續提昇血壓、心跳，及降低其心率變異性，而12小時日間輪班工作則較不顯著。在用混合迴歸模式控制其他干擾因子後，仍然可見夜間輪班工作會延緩收縮及舒張血壓值的恢復。結論是12小時夜間輪班工作，可以造成血壓及心跳上昇，及降低心率變異性，而且會延緩血壓的正常恢復。這些發現指出12小時夜間輪班工作，可能有不良的心血管效應。

Abstract Occupational cardiovascular diseases increased in association with the industrialization and globalization of working environments. However, the identification of work-related cardiovascular disease was often overlooked. This study was designed to investigate the cardiovascular effects of occupational status and 12-hour shift work. The first study: The relationship between time factors of elevated blood pressure (BP) and carotid atherosclerosis (CA) is still unclear. The associations between time-weighted average 24-hour ambulatory systolic BP (TWA-SBP), duration of hypertension in years (hypertension-year), and CA were investigated in a petrochemical company sample of 95 executives and 91 gender- and age-matched non-executives employees. Intima-media thickness (IMT) and plaque scores of extracranial carotid artery (ECCA) were determined bilaterally by high-resolution B-mode ultrasound. The determinants of segment-specific carotid IMT and odds ratios for CA, in terms of thicker IMT (IMT ≥75th percentile) and ECCA score ≥3, were evaluated by multivariate regression analysis. Results revealed TWA-SBP and hypertension-year were two major determinants of IMT at common carotid artery (CCA) and carotid bulb by using mixed regression models. However, TWA-DBP was a negative determinant of IMT at CCA and carotid bulb. Meanwhile, the executives were found to be a negative association with IMT at carotid bulb. Measurements at both internal carotid artery and bulb identified duration of diabetes mellitus as significant determinant of IMT. After controlling covariates, multivariate logistic regression analysis identified TWA-SBP and hypertension-year as the important determinants for thicker IMT and ECCA were determined bilaterally by high-resolution B-mode ultrasound. The determinants of segment-specific carotid IMT and odds ratios for CA, in terms of thicker IMT (IMT≧75th percentile) and ECCA score≧3, were evaluated by multivariate regression analysis. Results revealed TWA-SBP and hypertension-year were two major determinants of IMT at common carotid artery (CCA) and carotid bulb by using mixed regression models. However, TWA-DBP was a negative determinant of IMT at CCA and carotid bulb. Meanwhile, the executives were found to be a negative association with IMT at carotid bulb. Measurements at both internal carotid artery and bulb identified duration of diabetes mellitus as significant determinant of IMT. After controlling covariates, multivariate logistic regression analysis identified TWA-SBP and hypertension-year as the important determinants for thicker IMT and ECCA≧3. And, TWA-DBP was found as a negative determinant for CA. In conclusion, both TWA-SBP and hypertension-year were two major determinants for carotid IMT and CA, which seem to imply that both short-term and long-term durations of elevated BP are probably crucial in the pathogenesis of CA. The second study: Shift work has been associated with increased risk for cardiovascular disease. This study is designed to determine the hemodynamic effects during12-hour (12-h) shifts and changes in blood pressure (BP) and heart rate variability (HRV) for a 36-hour rest time following 12-h shifts. We recruited 15 male shift workers with a mean age of 32.9 years from a semiconductor factory. Ambulatory BP (AmBP) monitoring was performed for a total of 48-h for each participant. Forty-eight hours of Holter electrocardiogram monitoring was also performed in six workers each in day or night shifts. Paired self-comparison was used to estimate the difference between two hourly measurements using the same timetable intraindividually. Mixed models were constructed to estimate the effect of 12-h shift on delayed recovery of BP and heart rate (HR) in seven workers completed 96-h’s AmBP monitoring, including a 48-h night shift and another day shift period. Results showed compared with the effects of 12-h day shift work on the corresponding resting time, 12-h night shift work was found to have a persistent elevation of systolic and diastolic BP (SBP and DBP), and HR and a decrease in HRV. The delayed recovery of SBP and DBP also was found on the first 12-h rest time in night shift workers and was further demonstrated on the second 12-h rest time after adjustment for possible confounders through mixed models. In conclusions, 12-h night shift work may elevate BP, HR, and decrease HRV, and is associated with delayed recovery in SBP and DBP.