David J Hole, Charles R Gillis, Carol Chopra, Victor M Hawthorne
Objective-To assess the risk of cardiorespiratory symptoms and mortality in non-smokers who were passively exposed to environmental smoke. Design-Prospective study of cohort from general population first screened between 1972 and 1976 and followed up for an average of 11-5 years, with linkage of data from participants in the same household. Setting-Renfrew and Paisley, adjacent burghs in urban west Scotland. Subjects-15 399 Men and women (80% of all those aged 45-64 resident in Renfrew or Paisley) comprised the original cohort; 7997 attended for multiphasic screening with a cohabitee. Passive smoking and control groups were defined on the basis of a lifelong non-smoking index case and whether the cohabitee had ever smoked or never smoked. Main outcome measure-Cardiorespiratory signs and symptoms and mortality. Results -Each of the cardiorespiratory symptoms examined produced relative risks >1-0 (though none were significant) for passive smokers compared with controls. Adjusted forced expiratory volume in one second was significantly lower in passive smokers than controls. All cause mortality was higher in passive smokers than controls (rate ratio 1-27 (95% confidence interval 0-95 to 1-70)), as were all causes of death related to smoking (rate ratio 1-30 (0-91 to 1-85)) and mortality from lung cancer (rate ratio 2-41 (0.45 to 12.83)) and ischaemic heart disease (rate ratio 2-01 (1-21 to 3.35)). When passive smokers were divided into high and low exposure groups on the basis of the amount smoked by their cohabitees those highly exposed had higher rates of symptoms and death. Conclusion-Exposure to environmental tobacco smoke cannot be regarded as a safe involuntary habit.
West of Scotland Cancer Surveillance Unit, Ruchill Hospital, Glasgow G20 9NB David J Hole, MsC, statistician of lung