Mortality associated with passive smoking in Hong Kong
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《英国医生杂志》
1 Department of Community Medicine, University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, China, 2 Department of Health, Student Health Service, 4/F Lam Tin Polyclinic, Kowloon, Hong Kong, China, 3 Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX2 6HE
Correspondence to: T H Lam hrmrlth@hkucc.hku.hk
Introduction
Dose dependent associations between passive smoking and causes of death are consistent with previous findings for lung cancer and coronary heart disease and extend the evidence on stroke. Previous studies have shown associations between passive smoking and first acute strokes,3 4 and we have now shown a dose-response relation with mortality from stroke. Previous studies focused on ischaemic strokes but Chinese populations have a greater incidence of haemorrhagic stroke than do white populations,5 implying that many of the strokes in our study may have been non-ischaemic. Passive smoking probably affects all stroke subtypes, as does active smoking.
Our finding of a 34% increase in all cause mortality is consistent with but higher than that (15%) in the New Zealand cohort.1 Exposure to secondhand smoke at home is higher in Hong Kong than in New Zealand due to crowded living conditions. Before the 1990s, awareness of the danger of passive smoking was lower and smokers smoked freely at home.
We focused on passive smoking at home because the proxy reporter could most reliably supply these data, and we adjusted for education, which was also reliably recorded2 and is a good proxy for social class in Hong Kong. As data on cases and controls were derived from the same proxy, reporting bias should be minimal.2 If our results are not due to residual confounding, they provide further evidence that the dose-response associations between passive smoking and stroke and all cause mortality are likely to be causal.
See Editorial by Kawachi
This article was posted on bmj.com on 27 January 2005: http://bmj.com/cgi/doi/10.1136/bmj.38342.706748.47
We thank W L Cheung for help with analysis; the Immigration Department of the Government of the Hong Kong Special Administrative Region for data and assistance; and, in particular, the relatives who provided information.
Contributors: THL, SYH, AJH, KHM, and RP designed and carried out the study on which this analysis was based; SMcG, MS, LMH, and GNT planned and carried out this analysis; and all authors contributed to writing the paper. SMcG and THL are guarantors.
Funding: Hong Kong Health Services Research Committee (#631012) and Hong Kong Council on Smoking and Health.
Competing interests: THL is vice chairman and AJH a former chairman of the Hong Kong Council on Smoking and Health.
Ethical approval: Ethics Committee of the Faculty of Medicine, University of Hong Kong.
References
Hill SE, Blakely TA, Kawachi I, Woodward A. Mortality among never smokers living with smokers: two cohort studies, 1981-4 and 1996-9. BMJ 2004;328: 988-9.
Lam TH, Ho SY, Hedley AJ, Mak KH, Peto R. Mortality and smoking in Hong Kong: case-control study of all adult deaths in 1998. BMJ 2001;323: 361-2.
Bonita R, Duncan J, Truelson T, Jackson RT, Beaglehole R. Passive smoking as well as active smoking increases the risk of acute stroke. Tobacco Control 1999;8: 156-60.
Iribarren C, Darbinian J, Klatsky AL, Friedman GD. Cohort study of exposure to environmental tobacco smoke and risk of first ischemic stroke and transient ischemic attack. Neuroepidemiology 2004;23: 38-44.
Kay R, Woo J, Kreel L, Wong HY, Teoh R, Nicholls MG. Stroke subtypes among Chinese living in Hong Kong: the Shatin stroke registry. Neurology 1992;42: 985-7.(S M McGhee, associate professor1, S Y Ho)
Correspondence to: T H Lam hrmrlth@hkucc.hku.hk
Introduction
Dose dependent associations between passive smoking and causes of death are consistent with previous findings for lung cancer and coronary heart disease and extend the evidence on stroke. Previous studies have shown associations between passive smoking and first acute strokes,3 4 and we have now shown a dose-response relation with mortality from stroke. Previous studies focused on ischaemic strokes but Chinese populations have a greater incidence of haemorrhagic stroke than do white populations,5 implying that many of the strokes in our study may have been non-ischaemic. Passive smoking probably affects all stroke subtypes, as does active smoking.
Our finding of a 34% increase in all cause mortality is consistent with but higher than that (15%) in the New Zealand cohort.1 Exposure to secondhand smoke at home is higher in Hong Kong than in New Zealand due to crowded living conditions. Before the 1990s, awareness of the danger of passive smoking was lower and smokers smoked freely at home.
We focused on passive smoking at home because the proxy reporter could most reliably supply these data, and we adjusted for education, which was also reliably recorded2 and is a good proxy for social class in Hong Kong. As data on cases and controls were derived from the same proxy, reporting bias should be minimal.2 If our results are not due to residual confounding, they provide further evidence that the dose-response associations between passive smoking and stroke and all cause mortality are likely to be causal.
See Editorial by Kawachi
This article was posted on bmj.com on 27 January 2005: http://bmj.com/cgi/doi/10.1136/bmj.38342.706748.47
We thank W L Cheung for help with analysis; the Immigration Department of the Government of the Hong Kong Special Administrative Region for data and assistance; and, in particular, the relatives who provided information.
Contributors: THL, SYH, AJH, KHM, and RP designed and carried out the study on which this analysis was based; SMcG, MS, LMH, and GNT planned and carried out this analysis; and all authors contributed to writing the paper. SMcG and THL are guarantors.
Funding: Hong Kong Health Services Research Committee (#631012) and Hong Kong Council on Smoking and Health.
Competing interests: THL is vice chairman and AJH a former chairman of the Hong Kong Council on Smoking and Health.
Ethical approval: Ethics Committee of the Faculty of Medicine, University of Hong Kong.
References
Hill SE, Blakely TA, Kawachi I, Woodward A. Mortality among never smokers living with smokers: two cohort studies, 1981-4 and 1996-9. BMJ 2004;328: 988-9.
Lam TH, Ho SY, Hedley AJ, Mak KH, Peto R. Mortality and smoking in Hong Kong: case-control study of all adult deaths in 1998. BMJ 2001;323: 361-2.
Bonita R, Duncan J, Truelson T, Jackson RT, Beaglehole R. Passive smoking as well as active smoking increases the risk of acute stroke. Tobacco Control 1999;8: 156-60.
Iribarren C, Darbinian J, Klatsky AL, Friedman GD. Cohort study of exposure to environmental tobacco smoke and risk of first ischemic stroke and transient ischemic attack. Neuroepidemiology 2004;23: 38-44.
Kay R, Woo J, Kreel L, Wong HY, Teoh R, Nicholls MG. Stroke subtypes among Chinese living in Hong Kong: the Shatin stroke registry. Neurology 1992;42: 985-7.(S M McGhee, associate professor1, S Y Ho)