Healthy adults exposed to high levels of secondhand tobacco smoke show elevated C-reactive protein levels indicating chronic low-grade inflammation, according to a large database study.

The elevated CRP levels partly explain the higher than average risk of cardiovascular death among people exposed to secondhand smoke, said Mark Hamer, Ph.D., of the department of epidemiology and public health at University College, London, and his associates.

Noting that “very few large-scale, population-based studies have collected objective biochemical markers of secondhand smoke exposure with follow-up data on mortality,” the investigators did so using data from the Scottish Health Survey and the Health Survey for England. These are annual studies of nationally representative samples of British adults.

Dr. Hamer and his colleagues assessed data on 13,443 men and women aged 35 years and older who were free of cancer and cardiovascular disease at baseline and were followed for an average of 8 years. Exposure to secondhand smoke was determined by measuring salivary cotinine, and blood samples were analyzed for circulating CRP levels, according to the report in the Journal of the American College of Cardiology.

Approximately 21% of the subjects had high exposure to secondhand smoke.

During follow-up there were 1,221 deaths from all causes and 364 deaths from cardiovascular causes. Both types of mortality were associated with greater exposure to secondhand smoke.

Greater exposure to secondhand smoke also was associated with higher CRP levels, indicating chronic low-grade inflammation. This link “partly explained the elevated risk of CVD [cardiovascular disease] and all-cause death associated with high secondhand smoke [exposure],” the investigators said (J. Am. Coll. Cardiol. 2010;56:18-23).

In the subgroup of subjects who had never smoked, the risk of CVD-related death was twice as high among those with greater exposure to secondhand smoke as among those with lesser exposure. However, there was no significant association with CRP in this subgroup, indicating that some other mechanism must be responsible for the excess cardiovascular risk in these subjects.

There also was a significant association between secondhand smoke and all-cause mortality in never-smokers (hazard ratio 1.33) and in ex-smokers (HR 1.14).

In addition, there was no association between secondhand smoke exposure and CVD in the subgroup of ex-smokers. “This might be partly because ex-smokers already have heightened risk of CVD in comparison with never-smokers, thus secondhand smoke exposure might not add to existing risk. Indeed, inflammatory mediators like CRP are still significantly raised in ex-smokers up to 10-20 years after quitting,” Dr. Hamer and his associates noted.

This study was limited in that the data were incomplete on alcohol intake and body mass index, so these important risk factors could not be adjusted for in the analysis.

This study was supported in part by the British Heart Foundation, the Scottish Government Health Directorates, the U.K. Medical Research Council, the U.S. National Institutes of Health, the National Heart, Lung, and Blood Institute, the National Institute on Aging, the Academy of Finland, and Wellcome Trust. No financial conflicts of interest were reported.

Copyright (c) 2009 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

一项大型数据库研究显示，暴露于大量二手烟的健康成人可出现C反应蛋白(CRP)增高，提示慢性低度炎症。

 

伦敦大学学院流行病学和公共卫生系的Mark Hamer博士及其同事说，CRP水平增高可部分解释在二手烟暴露人群中心血管死亡的风险高于均值，。

由于“收集到二手烟暴露的客观生化标记物，并有死亡随访资料的以人群为基础的大型研究很少”，故研究者采用来自苏格兰健康调查和英格兰健康调查的数据进行了此项研究。这些调查每年进行1次，样本能够代表英国全国的成人。

 

Hamer博士及其同事评估了13,443名年龄在35岁及其以上的男性和女性的资料，这些人群在基线时没有癌症和心血管疾病，平均随访8年。根据美国心脏病学会杂志中一项报告，通过测量唾液中的可替宁和血标本中的循环CRP水平来确定二手烟暴露度。

 

大约21%的受试者其二手烟暴露程度高。

 

在随访期间，共有1,221例死亡，其中364例死于心血管疾病。这两种死亡均与二手烟暴露度较高有关。

 

二手烟暴露度较高也与CRP水平增高相关，CRP水平高提示慢性低度炎症。研究者认为，这种关联“可部分解释心血管疾病风险增高和与二手烟暴露度高有关的全因死亡。” (J. Am. Coll. Cardiol. 2010;56:18-23)。

 

在从不吸烟的受试者亚组中，二手烟暴露度较高者的CVD相关死亡的风险是二手烟暴露较少者的两倍。然而，该亚组与CRP无显著相关，提示在这些受试者中，存在一些与较高心血管风险有关的其他机制。

 

从不吸烟者(危险比 1.33)和曾经吸烟者(危险比 1.14)的二手烟暴露和全因死亡显著相关。

 

另外，在曾经吸烟者亚组中，二手烟暴露和CVD之间没有相关性。Hamer博士及其同事指出，“这部分因为同不吸烟者相比，曾经吸烟者已经增加了CVD的风险，因此二手烟暴露或许不会增加已经存在的风险。事实上，炎症介质，例如CRP，在戒烟长达10~20年的曾经吸烟者中显著增高。”。

 

这项研究存在局限性，即酒精摄入和体重指数的数据不完整，因此在该分析中没有对这些重要的危险因素进行校正。

 

该研究的部分资金来源于英国心脏基金会、苏格兰政府卫生局、英国医学研究理事会、美国国立卫生研究院、美国国家心肺血液研究所、美国国立老龄研究所、芬兰研究院和英国维康信托基金会。没有经济利益冲突报告。

 

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