The absolute risk of venous thrombosis after air travel: a cohort study of 8,755 employees of international organisations.
The absolute risk of venous thrombosis after air travel: a cohort study of 8,755 employees of international organisations.
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DOI：
10.1371/journal.pmed.0040290
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发表时间：
2007-09
期刊：
影响因子：
15.8
通讯作者：
Rosendaal FR
中科院分区：
文献类型：
--
作者：
Kuipers S;Cannegieter SC;Middeldorp S;Robyn L;Büller HR;Rosendaal FR
空中旅行后静脉血栓形成的风险大约增加2- 4倍，但绝对风险尚不清楚。本研究的目的是评估航空旅行后静脉血栓形成的绝对风险。我们在2000年1月1日至2005年12月31日期间对大型国际公司和组织的员工进行了一项队列研究。根据这些公司和组织提供的旅行记录评估，症状性静脉血栓的发生与接触航空旅行有关。长途飞行被定义为飞行至少4小时，参与者被认为在飞行后暴露了8周。在38910人年（PY）的总随访时间内，共有8755名员工接受了随访。员工在长途飞行中暴露的总时间为6,872日元。在随访期间，发生了53例血栓形成，其中22例发生在长途飞行的8周内，发病率为3.2/1,000 PY，而未暴露于航空旅行的个体发病率为1.0/1,000 PY（发病率比3.2,95%置信区间1.8-5.6）。这一比率相当于每4,656次长途飞行发生一次事故的风险。在较短时间内乘坐较多航班以及飞行时间增加，风险也会增加。发病率在旅行后2周最高，8周后逐渐降至基线。年龄在30岁以下的员工、使用口服避孕药的女性以及特别矮、特别高或特别超重的人患乳腺癌的风险尤其高。航空旅行后出现症状性静脉血栓形成的风险平均有中等程度的增加，并随着接触量的增加和高危人群的增加而增加。在一项对大型国际组织的8755名员工进行的队列研究中，苏珊娜·坎内吉特（Suzanne Cannegieter）及其同事发现，每4656次长途飞行就有一次血栓形成的风险。正常情况下，血液在人体中顺畅流动，为大脑和其他重要器官提供氧气和营养。当受伤发生时，一种叫做凝血因子的蛋白质使血液在受伤部位凝结或凝固。由此产生的血凝块（血栓）堵塞伤口，防止失血。然而，有时，血栓在未受伤的血管内形成，部分或完全阻塞血液流动。在身体深处的静脉（将血液输送到心脏的血管）中的血栓被称为深静脉血栓（DVT）。深静脉血栓的症状（通常发生在腿部的深静脉）包括一条腿的疼痛、肿胀和发红。深静脉血栓通常用肝素和华法林治疗，这两种抗凝药物可以阻止血栓的形成。如果不及时治疗，部分凝块（栓子）可能会脱落并进入肺部，在那里可能导致危及生命的肺栓塞（PE）。幸运的是，深静脉血栓和肺水肿是罕见的，但有遗传性凝血障碍，服用口服避孕药，以及某些类型的手术都是他们的危险因素。此外，长途飞机旅行增加了DVT和PE（统称为静脉血栓形成（VT））的风险2至4倍，部分原因是飞行期间强制固定减缓了血液流动。虽然在20世纪50年代首次注意到航空旅行和VT之间的联系，但究竟有多少人会在长途飞行后患上DVT和PE（患VT的绝对风险）仍然未知。这些信息是必要的，这样旅行者就可以得到有关实际风险的建议，并做出明智的决定，试图通过（例如）在飞行前服用小剂量的抗凝血药物来降低风险。在这项研究中，研究人员确定了一大群商务旅行者在长途航空旅行期间和之后患VT的绝对风险。研究人员从几家跨国公司和组织招募了近9000名员工，对他们进行了平均4.4年的跟踪调查。研究人员从公司记录中获取了每位员工乘坐航班的详细信息，并让员工完成了一份基于网络的调查问卷，询问他们是否患有VT，以及他们患有VT的风险因素是什么。在研究期间发生的53例血栓中，22例发生在长途飞行（飞行时间超过4小时）后的8周内。从这一点和员工在长途航班上花费的总时间的数据来看，研究人员计算出，这些航班使发生VT的风险增加了两倍，并且在此类旅行后不久发生VT的绝对风险（在特定时间段内发生某事的概率）是每4,656次航班发生一次。他们还计算出，在短时间和长时间的飞行中，乘坐更多的航班会增加VT的风险，并且在飞行后的前两周内风险最大。此外，年轻员工、服用口服避孕药的女性以及矮、高或超重的人患VT的风险尤其高。本研究的主要发现是长途飞行后发生VT的绝对风险很低，在近5000名乘客中只有1人可能因为飞行而发生VT。然而，这项研究只包括了平均年龄为40岁的健康人群，他们以前没有静脉血栓，所以长途飞行后静脉血栓的绝对风险可能在普通旅行人群中更高。即便如此，这一发现强烈表明，所有长途旅行者预防性使用抗凝血剂可能并不合理，因为这些药物有潜在的危险副作用（例如，它们可能导致无法控制的出血）。然而，有额外VT危险因素的旅行者亚组可能从使用这种和其他预防措施中受益，但需要随机试验来找出谁将从哪种预防措施中受益最多。请通过本摘要的在线版本http://dx.doi.org/10.1371/journal.pmed.0040290访问这些网站。MedlinePlus百科全书中关于血栓、深静脉血栓和肺栓塞的页面（英文和西班牙文）包括一个关于深静脉血栓形成的动画，来自英国国家卫生服务机构的患者信息，关于深静脉血栓形成的直接健康百科全书（几种语言），来自美国疾病控制和预防中心以及英国国家旅行健康网络和中心的深静脉血栓形成旅行者信息。这项研究来自世卫组织全球旅行危害研究（WRIGHT）项目，以及世卫组织关于航空旅行和静脉血栓栓塞的WRIGHT项目。他的研究是其中的一部分，有一个网站
The risk of venous thrombosis is approximately 2- to 4-fold increased after air travel, but the absolute risk is unknown. The objective of this study was to assess the absolute risk of venous thrombosis after air travel. We conducted a cohort study among employees of large international companies and organisations, who were followed between 1 January 2000 and 31 December 2005. The occurrence of symptomatic venous thrombosis was linked to exposure to air travel, as assessed by travel records provided by the companies and organisations. A long-haul flight was defined as a flight of at least 4 h and participants were considered exposed for a postflight period of 8 wk. A total of 8,755 employees were followed during a total follow-up time of 38,910 person-years (PY). The total time employees were exposed to a long-haul flight was 6,872 PY. In the follow-up period, 53 thromboses occurred, 22 of which within 8 wk of a long-haul flight, yielding an incidence rate of 3.2/1,000 PY, as compared to 1.0/1,000 PY in individuals not exposed to air travel (incidence rate ratio 3.2, 95% confidence interval 1.8–5.6). This rate was equivalent to a risk of one event per 4,656 long-haul flights. The risk increased with exposure to more flights within a short time frame and with increasing duration of flights. The incidence was highest in the first 2 wk after travel and gradually decreased to baseline after 8 wk. The risk was particularly high in employees under age 30 y, women who used oral contraceptives, and individuals who were particularly short, tall, or overweight. The risk of symptomatic venous thrombosis after air travel is moderately increased on average, and rises with increasing exposure and in high-risk groups. In a cohort study of 8,755 employees of large international organizations followed for 38,910 person-years, Suzanne Cannegieter and colleagues find a risk of one thrombosis per 4,656 long-haul flights. Blood normally flows smoothly throughout the human body, supplying the brain and other vital organs with oxygen and nutrients. When an injury occurs, proteins called clotting factors make the blood gel or coagulate at the injury site. The resultant blood clot (thrombus) plugs the wound and prevents blood loss. Sometimes, however, a thrombus forms inside an uninjured blood vessel and partly or completely blocks the blood flow. A clot inside one of the veins (vessels that take blood to the heart) deep within the body is called a deep vein thrombosis (DVT). Symptoms of DVT (which usually occurs in the deep veins of the leg) include pain, swelling, and redness in one leg. DVT is usually treated with heparin and warfarin, two anticoagulant drugs that stop the blood clot growing. If left untreated, part of the clot (an embolus) can break off and travel to the lungs, where it can cause a life-threatening condition called pulmonary embolism (PE). Fortunately, DVT and PE are rare but having an inherited blood clotting disorder, taking an oral contraceptive, and some types of surgery are all risk factors for them. In addition, long-haul plane travel increases the risk of DVT and PE, known collectively as venous thrombosis (VT) 2- to 4-fold, in part because the enforced immobilization during flights slows down blood flow. Although the link between air travel and VT was first noticed in the 1950s, exactly how many people will develop DVT and PE (the absolute risk of developing VT) after a long flight remains unknown. This information is needed so that travelers can be given advice about their actual risk and can make informed decisions about trying to reduce that risk by, for example, taking small doses of anticoagulant medicine before a flight. In this study, the researchers have determined the absolute risk of VT during and after long-haul air travel in a large group of business travelers. The researchers enrolled almost 9,000 employees from several international companies and organizations and followed them for an average of 4.4 years. The details of flights taken by each employee were obtained from company records, and employees completed a Web-based questionnaire about whether they had developed VT and what risk factors they had for the condition. Out of 53 thrombi that occurred during the study, 22 occurred within eight weeks of a long-haul flight (a flight of more than four hours). From this and data on the total time employees spent on long-haul flights, the researchers calculated that these flights tripled the risk of developing VT, and that the absolute risk (the probability of something occurring in a certain time period) of a VT occurring shortly after such travel was one event per 4,656 flights. They also calculated that the risk of VT was increased by exposure to more flights during a short period and to longer flights and was greatest in the first two weeks after a flight. In addition, the risk of VT was particularly high in young employees, women taking oral contraceptives, and people who were short, tall or overweight. The main finding of this study is that the absolute risk of VT after of a long-haul flight is low—only one passenger out of nearly 5,000 is likely to develop VT because of flying. However, the study included only healthy people without previous VT whose average age was 40 years, so the absolute risk of VT after long-haul flights might be higher in the general traveling population. Even so, this finding strongly suggests that prophylactic (preventative) use of anticoagulants by all long-haul travelers may not be justified because these drugs have potentially dangerous side effects (for example, they can cause uncontrolled bleeding). Subgroups of travelers with additional risk factors for VT might, however, benefit from the use of this and other prophylactic measures, but randomized trials are needed to find out who would benefit most from which prophylactic measure. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040290. MedlinePlus encyclopedia pages on blood clots, deep vein thrombosis, and pulmonary embolism (in English and Spanish) Information from the US National Heart Lung and Blood Institute on deep vein thrombosis, including an animation of how DVT causes pulmonary embolisms Information for patients from the UK National Health Service Direct health encyclopedia on deep vein thrombosis (in several languages) Information for travelers on DVT from the US Centers for Disease Control and Prevention and from the UK National Travel Health Network and Centre This study came out of the WHO Research Into Global Hazards of Travel (WRIGHT) project, and WHO's WRIGHT project on Air Travel and Venous Thromboembolism, of which his study forms a part, has a Web site
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