吸烟者戒烟后猝死风险下降

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吸烟者戒烟后猝死风险下降

护理健康研究表明，吸烟者有发生心源性猝死的风险，但是戒烟可以降低该风险，并且随着时间的延续，可以使其降低到从未吸烟者的水平。

根据埃德蒙顿的亚伯达大学的医学博士Roopinder Sandhu和来自波士顿的布里格姆与妇女医院和哈佛公共卫生学院的同事的报导，经过30年的随访后，当与从未吸烟者进行比较时，吸烟发生心源性猝死的风险更高，并且差异具有统计学意义。

研究者在《Arrhythmiaand Electrophysiology》在线报导，总体来说，曾经的吸烟者有高危险，不过它随着戒烟时间的延长，该风险会稳定下降，并且戒烟20年到达从未吸烟者的水平。

“我们的研究结果进一步论证了与吸烟有关的心源性猝死是可以改变的这一重要观点”他写道，补充说“这说明在预防女性心源性猝死的发生时，应该包括积极的戒烟措施.”

尽管吸烟是众所周知的心原性猝死和冠心病的高危因素，很少研究对发病风险与吸烟的数量，吸烟的持续时间，戒烟的关系进行研究。

Sandhu和他的同事利用自于护理健康研究（队列研究）的101018位女性的资料对该问题进行了分析。该队列中的女性，在1980年进入队列时没有患有冠心病，中风，或是癌症；其中29.1%是目前的吸烟者，26.4%是过去的吸烟者，44.5%是从未吸烟者。研究者在该研究上对吸烟状况改变做出了解释。
到2010年为止，有351例心原性猝死（病例），这些病例是通过医学记录，尸解报告，和家人观察得到的。

除了吸烟状态外，在调整多个冠心病危险因素后，每天吸烟的数量和吸烟的持续时间与心源性猝死风险直线相关，这些被调整的危险因素包含年龄、饮食、高血压、高血脂胆固醇、体质指数、饮酒、身体锻炼、更年期的情形和停经后的激素使用、阿司匹林的使用、各种维生素和维生素E以及心肌梗死的家族史。

即使是少量吸烟到中等程度的吸烟者—每天1到14支—其发生心源性猝死的风险也比从不吸烟的人高。

持续吸烟每增加5年，其心源性猝死发生风险将增加8%(HR 1.08, 95% CI 1.05 to 1.12)

然而，戒烟与降低风险。与比较持续吸烟者相比，戒烟达20年者其心源性猝死的发生风险显著降低，会降低到与过去吸烟者(HR 0.45, 95% CI 0.31 to 0.64)和这些这些从未吸烟者相似的水平(HR 0.40, 95% CI 0.30 to 0.54)。


与随访过程中发生冠心病者（戒烟少于5年vs. 15~20年）相比，戒烟后该风险的下降在那些在随访过程中没有发生冠心病的女性下降的更迅速。

“有冠心病的女性，”作者解释：“严重和/或易发生损害的冠状动脉粥样硬化斑块及继发的心肌纤维化和瘢痕可能会导致持续性的心源性猝死的风险，这个风险在戒烟后会持续一段时间。”

他说，“越直接的……在没有冠心病的女性的中观察风险会降低，可部分的被尼古丁的促心律不齐效应所解释，就如减少儿茶酚胺的释放，钾的运转的改变，由一过性的血小板粘附引起的心室颤阈值降低。”

研究者承认了该研究的一些局限性，包括了根据自述的吸烟量可能带来错误的分析，在判定心源性猝死时可能出现错误；在随访期间严重冠心病的事件信息的缺乏，可能存在参与混杂及未测量的混杂因素。

除此之外，这个人群的研究是白人女护士，该研究结果可能不适用于其他人群。

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Smokers are at risk for sudden cardiac death, but quitting can reduce that risk over time to levels seen among those who never smoked, an analysis of the Nurses' Health Study showed.

Through a follow-up of 30 years, the risk of sudden cardiac death was significantly greater among smokers when compared with those who never smoked (HR 2.44, 95% CI 1.80 to 3.31), according to Roopinder Sandhu, MD, of the University of Alberta in Edmonton, and colleagues from Brigham & Women's Hospital and the Harvard School of Public Health, Boston.

Past smokers also had an elevated risk overall (HR 1.40, 95% CI 1.10 to 1.79), although it steadily declined with an increasing duration of cessation, reaching a level of risk within 20 years that was comparable to risk of those who never smoked, the researchers reported online in Circulation: Arrhythmia and Electrophysiology.

"Our data reinforces the important concept that sudden cardiac death risk associated with cigarette smoking is modifiable," they wrote, adding that "this suggests efforts to prevent sudden cardiac death among women should include aggressive strategies for smoking cessation."

Although smoking is a well-known risk factor for sudden cardiac death and coronary heart disease, few studies have examined the relationships between risk and quantity of cigarettes smoked, smoking duration, and smoking cessation.

Sandhu and colleagues explored those issues using data from the Nurses' Health Study on 101,018 women without known coronary heart disease, stroke, or cancer at baseline in 1980; 29.1% were current smokers, 26.4% were past smokers, and 44.5% had never smoked at baseline. The researchers accounted for changes in smoking status during the study.

Through 2010, there were 351 sudden cardiac deaths confirmed through medical records, autopsy reports, and interviews with family members.

In addition to smoking status, both quantity of cigarettes smoked each day and smoking duration were associated in a linear fashion with sudden cardiac death risk after adjustment for several coronary heart disease risk factors, including age, diabetes, hypertension, hypercholesterolemia, body mass index, alcohol use, physical activity, menopausal status and postmenopausal hormone use, use of aspirin, multivitamins, and vitamin E, and family history of MI (P<0.0001 for both trends).

Even a small-to-moderate amount of smoking -- one to 14 cigarettes a day -- was associated with a higher risk compared with never smoking (HR 1.84, 95% CI 1.16 to 2.92).

Every 5 years of continued smoking was associated with an 8% greater risk of sudden cardiac death (HR 1.08, 95% CI 1.05 to 1.12).

Quitting, however, was associated with a declining risk. Within 20 years of quitting, the risk of sudden cardiac death -- compared with continuing smokers -- was similarly reduced in both past smokers (HR 0.45, 95% CI 0.31 to 0.64) and those who had never smoked (HR 0.40, 95% CI 0.30 to 0.54).

That reduction in risk after quitting was more rapid among the women who did not develop coronary heart disease during follow-up compared with those who did (less than 5 years versus 15 to 20 years).

In women with coronary heart disease, the authors explained, "severe and/or vulnerable coronary atherosclerotic plaques and resultant myocardial fibrosis and scarring may confer a residual sudden cardiac death risk which persists for some time after smoking cessation."

"In contrast," they wrote, "the more immediate ... risk reduction observed among women without coronary heart disease may, in part, be explained by alleviation of acute pro-arrhythmic effects of nicotine such as reductions in catecholamine release, alteration of potassium handling, and lowering of ventricular fibrillation threshold caused by transient enhanced platelet adhesion."

The researchers acknowledged some limitations of the study, including possible misclassification of cigarette consumption based on self-report, possible error in determining sudden cardiac death, the lack of information about the severity of coronary heart disease events during follow-up, and potential residual or unmeasured confounding.

In addition, the study population was mostly white, female nurses, and the findings may not apply to other groups.