News Author: Lisa Nainggolan – CME Author: Laurie Barclay, MD – From Heartwire — a professional news service of WebMD | September 22, 2008
Chinese researchers have reported, for the first time, a link between exposure to passive smoke and peripheral arterial disease (PAD) in a cohort of women who have never smoked. Dr Yao He (Chinese PLA General Hospital, Beijing, China) and colleagues publish their findings today in Circulation [1].
“We found that compared with women who were not exposed to secondhand smoke (SHS), among women who were exposed to SHS, the risk of intermittent claudication was increased by 87% and risk of PAD — assessed by ankle-brachial index < 0.90 — was increased by 47%, with significant dose-response relationships for both number of cigarettes exposed to and duration of exposure,” they state.
In line with previous studies, He et al also found an increased risk of both coronary heart disease and stroke in the women exposed to passive smoking, with this being the first study to specifically report a positive association between SHS and ischemic but not hemorrhagic stroke.
“In China, only 4% of women are current smokers, but more than 50% of women are exposed to SHS,” they note. “But most people [there] are unaware of the serious health hazards of SHS. Thus, urgent public health measures are warranted to protect individuals from exposure to SHS.”
Passive smoking linked with ischemic, but not hemorrhagic stroke
The researchers explain that China is the largest producer and consumer of tobacco in the world, with its 350 million smokers puffing their way through 30% of the globe’s cigarettes. But awareness of the health hazards of either active or passive smoking is still low.
They set out to examine the relationship between SHS and cardiovascular diseases, particularly PAD and stroke, in older Chinese women (60 years or older) who had never smoked from a population-based cross-sectional study in Beijing. SHS was defined as exposure to another person’s tobacco smoke at home or in the workplace.
“Because the vast majority of women were never smokers (87%) we had a unique opportunity to evaluate the association of SHS with risk of CVD [cardiovascular disease], particularly PAD,” they note.
After adjustment for 13 potential confounding factors, they found that women who had been exposed to SHS had a significantly higher risk of coronary heart disease (CHD; adjusted odds ratio [OR] 1.69; p<0.001) and ischemic stroke (OR 1.56; p = 0.035) than those never exposed to SHS.
The adjusted OR’s of PAD defined by intermittent claudication (IC), by ankle-brachial index (ABI) < 0.90 and by either IC or ABI < 0.90 were: 1.87 ( p=0.001), 1.47 (p=0.018) and 1.67 (p<0.001) respectively.
Dose-response relationships were found between SHS exposure amount (cigarettes per day) and duration (minutes per day) and increasing prevalence of CHD, ischemic stroke and PAD.
“Our finding of a dose-dependent association of SHS with CHD is consistent with the literature,” He et al explain. They also note that their findings with regard to stroke support previous studies, but that many of these did not investigate subtypes of stroke.
“This population based study is the first to report a positive association of SHS exposure with ischemic stroke but not hemorrhagic stroke among Chinese female nonsmokers.”
PAD underdiagnosed and undertreated in China
An important advantage of the study, say He et al, was that PAD was diagnosed by ABI measurement. They explain that PAD is an underdiagnosed and undertreated condition in China: previous studies have shown almost 50% of PAD patients are asymptomatic and most of them are unaware of their condition.
“To the best of our knowledge, this is the first study showing an increased risk of PAD with increasing SHS exposure,” they note, adding that they believe their results are generalizable to similar populations in China.
“SHS exposure in women is highly prevalent in China. In addition to being a causal factor for CHD, SHS should be considered an important risk factor for ischemic stroke and PAD in Chinese women who never smoked,” they conclude.
This study is supported by research grants from the National Natural Science Foundation of China, Beijing Natural Science Foundation, and the Health Service in the Health Ministry of China. Dr Hu was partly supported by an American Heart Association Established Investigator Award. Coauthor Dr. He was partly supported by the Gordon Wu and Cheng YuTung Exchange Professorships in the Faculty of Medicine at the University of Hong Kong. The other study authors have disclosed no relevant financial relationships.
Source
1. He Y, Lam TH, Jian B et al. Passive smoking and risk of peripheral arterial disease and ischemic stroke in Chinese women who never smoked. Circulation. 2008:doi: 10.1161/CIRCULATIONAHA.108.784801.
Clinical Context
There is strong evidence to date that SHS exposure is a causal factor for CHD. However, the relationship between SHS exposure and ischemic stroke and PAD is still unclear.
Several studies suggest a positive association between SHS and the risk for stroke. There have been recent estimates of the prevalence of PAD attributable to active smoking in a Chinese population, but no study to date has reported on the association of SHS with PAD.
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Medscape Medical News 2008. ©2008 Medscape
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