Passive Smoking and Associated Causes of Death in Adults in Scotland

Transcription

1 Passive Smoking and Associated Causes of Death in Adults in Scotland 2005 P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 1

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3 Passive Smoking and Associated Causes of Death in Adults in Scotland 2005 David J Hole Professor of Epidemiology and Biostatistics Public Health and Health Policy Division of Community Based Sciences University of Glasgow This research was funded by the Scottish Executive and commissioned on their behalf by NHS Health Scotland. The views expressed here are those of the author and should not be attributed to any of the funding bodies. Report available at: P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 3

4 Published by Health Scotland. Edinburgh Office: Woodburn House, Canaan Lane, Edinburgh EH10 4SG Glasgow Office: Clifton House, Clifton Place, Glasgow G3 7LS NHS Health Scotland and the author, ISBN: X 4

5 Contents Executive summary 7 1 Study aim 8 2 Methods 8 3 Analysis Measurement of second-hand smoke exposure Lung cancer Ischaemic heart disease Stroke Respiratory disease (excluding lung cancer) 14 4 Discussion 17 Appendix 20 P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 5

6 Tables Table 3.1 Total number of lung cancer deaths in Scotland by sex and 10 smoking category Table 3.2 Total number of lung cancer deaths in lifelong non-smokers by ETS 11 exposure category Table 3.3 Total number of ischaemic heart disease deaths in Scotland by sex 12 and smoking category Table 3.4 Total number of IHD deaths in lifelong non-smokers by ETS 13 exposure category Table 3.5 Total number of stroke deaths in Scotland by sex and 13 smoking category Table 3.6 Total number of stroke deaths in lifelong non-smokers by 14 ETS exposure category Table 3.7 Total number of respiratory disease deaths in Scotland by sex and 15 smoking category Table 3.8 Total number of respiratory disease deaths in lifelong non-smokers 15 by ETS exposure category Table 3.9 Summary of number of deaths (four causes) attributable to active 16 and passive smoking Table A1 Estimated deaths using alternative smoking prevalence data 21 Table A2 Estimated deaths using alternative relative risk for active smoking 22 and lung cancer Table A3 Estimated deaths assuming different latencies for vascular and 23 respiratory deaths 6

7 Executive summary Estimates of the numbers of deaths among adults in Scotland caused by exposure to environmental tobacco smoke (ETS) have been calculated using local data on the distribution of exposure categories where possible and international estimates of the level of risk posed. Four major disease categories have been considered as they are the causes of death most strongly related to smoking and unsurprisingly are the main causes of death in Scotland: lung cancer, ischaemic heart disease (IHD), stroke and respiratory disease. The objective of the report is to estimate how much past ETS exposure impacts on current levels of these four causes of death in Scotland. As most available data relate to the impact of ETS exposure on lifelong non-smokers, estimates have been made specifically for this sub-group of individuals. ETS exposure is associated with 865 deaths per year in Scotland among lifelong non-smokers from the four main causes listed. Individually, this divides into 395 IHD deaths, 335 stroke deaths, 91 respiratory death and 44 lung cancer deaths. Over 75% of the ETS-related deaths occur amongst women. Including other diseases known to be related to smoking, up to 1,000 deaths per year might be attributed to ETS exposure among lifelong non-smokers. Whilst it is extremely difficult to quantify the risk of ETS exposure to ex-smokers as no reliable information exists, there would appear to be as many ex-smoking men and women exposed to ETS as there are lifelong non-smokers. It would not be unreasonable to assume that they are at similar risk after a suitable latent period and that the numbers of ETS-related deaths would be similar to those seen for lifelong non-smokers. This would imply that some 1,500 to 2,000 deaths per year in Scotland are related to ETS exposure among non-smokers (lifelong or quitters). Passive smoking represents the greatest risk to public health when compared to other forms of involuntary environmental exposure. A ban on smoking in the workplace might be considered to be capable of reducing the number of ETS-related deaths by however much it reduces the total ETS exposure in individuals (e.g. 50% reduction in total ETS exposure might lead to a 50% reduction in ETS-related deaths). It should be recognised that there is a substantial benefit to be gained from such a ban in terms of the impact it would have on active smoking rates. A modest reduction in active smoking rates would have major benefits in terms of reducing numbers of deaths among the Scottish population generally. P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 7

8 1 Study aim To estimate the number of deaths from the major smoking-related causes of death in Scottish adults which can be attributed to passive smoking. 2 Methods To use appropriate local information where possible and international estimates where this is not feasible, with sensible adjustments for local conditions. Note: Environmental tobacco smoke (ETS), second-hand smoke and passive smoking are used interchangeably in this report. 3 Analysis 3.1 Measurement of second-hand smoke exposure It is extremely difficult to measure the amount of second-hand smoke experienced by individuals and impossible to produce a direct measure of an individual s cumulative exposure, the more relevant aetiological factor. Early studies of the impact of passive smoking used as a pragmatic indicator, marriage to a smoker, and most of these studies concentrated on lifelong non-smoking wives as the index group. This turned out to be a sensible choice as when studies of the levels of urinary and serum cotinine were conducted among passive smokers (non-smoking women married to smoking men) and controls (non-smoking women married to non-smoking men), there was a substantial difference in mean levels. This meant that passive smokers as a group experienced higher cotinine levels than controls, which was the important issue, even though a small number of controls had higher individual levels than a small number of passive smokers. The use of such a definition was supported by questionnaire evidence that passive smokers at home were also more likely to accept passive exposure at work or in other social circumstances. Later studies concentrated on exposures both at home, at work and in other circumstances and consistently observed increased risks in relation to exposures in the different settings. More recently, the British Regional Heart Study has reported risks of coronary heart disease and stroke in relation to serum cotinine measures directly among non-smokers and has observed markedly increased risks for the former disease. Thus, we can conclude that the use of definitions such as married to a smoker is valid as an indicator of increased exposure. Indeed, they may well be conservative in trying to estimate the true risk of passive exposure. 8

9 3.2 Lung cancer It is widely accepted that passive exposure to cigarette smoke can cause lung cancer among those who have never smoked. ETS is classified as a Class 1 (strong epidemiological and biological human and animal evidence) carcinogen by IARC, the International Agency for Research on Cancer. How risky is passive smoking in relation to lung cancer? The interpretation of the evidence linking exposure to second-hand smoke with lung cancer is constrained by the imprecision of risk estimates. This is especially true for Scotland as there are few studies locally which have attempted to make such an estimate and all have been based on very small numbers of passively exposed cases. The most recent international analysis, which is based on large numbers of cases and includes adjustment for potential confounders and exposure misclassification, has been produced by the International Agency for Research on Cancer (IARC) in the International Journal of Cancer in 2004 (Brennan, 2004). This concludes that there is a clear dose response relationship consistent with a causal association between exposure to second-hand smoke and the development of lung cancer among never smokers. The risk estimates are set at 16 to 18% for average exposure and up to 32% for long-term exposure from combined spousal, workplace and social sources. How do these estimates relate to the Scottish situation? Two relevant factors pertain. First, the degree of passive exposure will almost certainly be related to the extent of active smoking. As Scotland has been known historically as the lung cancer capital of the world, it would seem reasonable to infer that the level of active smoking has been markedly higher than other places in the world (particularly those taking part in the above-mentioned international study). Therefore, the level of passive exposure locally will have been higher and it would seem reasonable to increase the magnitude of the estimates quoted. Secondly, all studies into the effects of passive smoking tend to use as a control group never-smokers married to never-smokers (or some equivalent for workplace exposure). However, studies of urinary cotinine levels in this type of control group have found that over 60% have detectable levels in other words the control groups themselves are substantially contaminated. Again, this figure of 60% may be a conservative estimate as far as Scotland is concerned. It is impossible to quantify with any precision by how much the Scottish estimate should be increased and in this document we are arbitrarily setting the average exposure risk at 25%. P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 9

10 What proportion of the non-smoking population is exposed to second-hand smoke? The objective in this part of the report is to try and estimate how much past exposure impacts on current lung cancer levels in Scotland. As there is a substantial lead-time between exposure and development of lung cancer a minimum of 20 years and up to 40 years we are consequently looking for smoking data from some 30 years ago. It is extremely fortuitous that data from the Renfrew/Paisley survey conducted by Professor Victor Hawthorne is available for that time period. As this was a population-based study and co-habitees (mostly husbands and wives) took part in large numbers it also provides valuable data on spousal exposure. This suggested that only about 19% of men were lifelong nonsmokers and about one-third of these (6%) were regularly exposed to second-hand smoke at home. Some 46% of women were lifelong non-smokers and about three-quarters of these (32%) were passively exposed at home. The majority of women were not working at that time and their total passive exposure derived mainly from the home situation. Men however derived substantial exposures at work although those exposed at home were more likely to be in contact with second-hand smoke at work. The revised figures for regular exposure from either source have been taken as 12% for men and 33% for women. The total number of lung cancer deaths occurring each year in Scotland is approximately 2,300 among men and 1,700 in women. These deaths can be distributed among the different smoking categories as shown in Table 3.1. Table 3.1 Total number of lung cancer deaths in Scotland by sex and smoking category Smoking category Relative risk* Percentage of men in each smoking category group* Men Number of lung cancer deaths by smoking group Percentage of women in each smoking category group* Women Number of lung cancer deaths by smoking group Never 1 19% 82 46% cigs/day 5 12% % cigs/day 8 29% 1,005 24% cigs/day 10 16% 693 3% 133 Ex-smokers % 260 8% 89 Total deaths** 2,300 1,700 *Relative risk estimates and smoking prevalence figures derived from the Renfrew/Paisley survey. **This includes 1,867 male and 1,256 female lung cancer deaths attributable to active smoking. Thus, we would estimate that the annual number of lung cancer deaths occurring among lifelong non-smokers in Scotland totals 82 for men and 204 for women. The number of lung cancer deaths in Scotland annually caused by active smoking is 81% (male) and 74% (female). This amounts to 1,867 in men and 1,256 among women, a total of over 3,100 lung cancer deaths. 10

11 The distribution of the 82 (male) and 204 (female) lung cancer deaths in lifelong non-smokers among those who have and have not been passively exposed is shown in Table 3.2. Table 3.2 Total number of lung cancer deaths in lifelong non-smokers by ETS exposure category ETS exposure Relative risk of lung cancer Percentage of never-smokers in each group Men Number of lung cancer deaths Percentage of never-smokers in each group Women Number of lung cancer deaths No 1 33% 23 25% 43 Yes % 59 75% 161 This implies that 220 ( ) lung cancer deaths occur among lifelong nonsmokers who are passively exposed. However, not all of these deaths can be directly attributed to passive exposure. The attributable risk figures for passive smoking among lifelong non-smokers and lung cancer are 14% (12 men) and 16% (32 women). This amounts to 44 lung cancer deaths per year for both sexes combined. This figure may seem very low. Paradoxically, this reflects the fact that the active smoking prevalence for Scotland has historically been so high up to 80% eversmoked among adult men and 55% among adult women. Thus the contribution of passive as opposed to active exposure to cigarette smoke is minimal in that there have been few men and a minority of women who experience passive exposure only. There is some evidence that ex-smokers have an increased risk of lung cancer due to subsequent passive exposure but no evidence that active smokers have increased risks due to additional passive exposure. Thus the bottom line for Scotland at present is that of the 4,000 lung cancer deaths occurring annually, over 3,100 are caused by active smoking and about 50 are caused by passive exposure. 3.3 Ischaemic heart disease Numerous studies have shown that individuals who smoke are at an increased risk of developing and dying from IHD. What is less understood is the mechanism by which this occurs. Whether smoking directly causes IHD or exacerbates other mechanisms is not clear. In contrast to lung cancer and respiratory disease, the dose response relationship between amount smoked among active smokers and IHD risk is weak. This would seem to suggest that cigarette smoking per se is the critical risk factor and not the amount smoked. This has led to considerable controversy about the magnitude of IHD risk associated with passive exposure. Some argue that if the ratio of the dose of passive to active smoking seen in lung P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 11

12 cancer risk (between 1 in 50 to 1 in 100) is transferred to IHD risk, then this latter risk associated with passive exposure is negligible. Alternatively, as smoking or not smoking is more critical than amount smoked for active smokers, then passive exposure would represent a more substantial risk than simply applying a direct calibration of dose received. The epidemiological evidence would seem to support this latter argument. Even so, the estimates derived to date for IHD risk associated with passive smoking do seem to be on the high side and it is possible that some, but not all, of this excess risk is due to misclassification of passive smoking status or unexplained confounding, a problem which led to some of the early estimates for lung cancer being on the high side. Taking the estimates suggested by the review by Law et al. (1977), and using the same method as above for lung cancer, we estimate there are 758 male IHD deaths annually in Scotland and 1,814 IHD female deaths among lifelong non-smokers in Scotland (Table 3.3). Table 3.3 Total number of ischaemic heart disease deaths in Scotland by sex and smoking category Smoking category Relative risk of IHD Percentage in each smoking category Men Number of IHD deaths Percentage in each smoking category Women Number of IHD deaths Never 1 19% % 1, cigs/day % % 1, cigs/ day % 2,256 24% 1, cigs/day % 1,156 3% 214 Ex-smokers % 1,254 8% 413 Total deaths* 6,200 5,500 *This includes 2,210 male and 1,557 female IHD deaths attributable to active smoking. Table 3.4 opposite shows the distribution of the 758 male IHD deaths and 1814 female IHD deaths in lifelong non-smokers between those who have and those who have not been passively exposed to ETS. From the table it can be seen that 544 IHD deaths occur amongst male lifelong non-smokers and 1,432 IHD deaths amongst female lifelong non-smokers who have been exposed to ETS. Of these, 109 male IHD cases and 286 IHD cases can be attributed to passive smoking. 12

13 Table 3.4 Total number of IHD deaths in lifelong non-smokers by ETS exposure category ETS exposure Relative risk of IHD Percentage of never-smokers in each group Men Number of IHD deaths Percentage of never-smokers in each group Women Number of IHD deaths No 1 33% % 382 Yes % % 1, Stroke Very little information exists about the risk of stroke in relation to ETS. Studies in New Zealand and the USA have produced positive associations, although the magnitudes have varied substantially. The former estimated the excess risk at 82% and the latter at 29%. When compared with the risk observed in studies of active smokers generally, the former figure appears high. I have therefore taken the lower figure as the true estimate as it appears more plausible in relation to active smoking and stroke and because it is of the same order of magnitude as that observed for IHD, as IHD and stroke share similar levels of risk for active smoking. We estimate that there are about 2,500 male stroke deaths and 4,250 female stroke deaths annually in Scotland (Table 3.5). Table 3.5 Total number of stroke deaths in Scotland by sex and smoking category Smoking category Relative risk of stroke Percentage in each smoking category Men Number of Stroke deaths Women Percentage in each smoking category Number of Stroke deaths Never 1 19% % 1, cigs/day % % cigs/day % % 1, cigs/day % 522 3% 180 Ex-smokers % 444 8% 273 Total deaths* 2,500 4,250 *This including 668 male and 872 female stroke deaths attributable to active smoking. P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 13

14 Table 3.6 shows the distribution of the 348 male stroke deaths and 1,554 female stroke deaths in lifelong non-smokers between those who have and those who have not been passively exposed to ETS. In total there are 252 deaths amongst male and 1,235 deaths amongst female lifelong non-smokers exposed to ETS due to stroke. Of these, 57 male stroke deaths and 278 female stroke deaths can be attributed to passive smoking. However, it should be noted that these estimates are based on a limited number of studies and further epidemiological studies are required to refine them. Table 3.6 Total number of stroke deaths in lifelong non-smokers by ETS exposure category ETS Exposure Relative risk of stroke Percentage of never-smokers in each group Men Number of stroke deaths Percentage of never-smokers in each group Women Number of stroke deaths No 1 33% 96 25% 319 Yes % % 1, Respiratory disease (excluding lung cancer) Given that the risk of respiratory disease is increased among active smokers, and that there is good evidence that respiratory function, particularly FEV 1 (forced expiratory volume in one second), is impaired among lifelong non-smokers who are exposed to second-hand smoke, it seems entirely plausible that respiratory disease should be included among the diseases affected by passive smoking. Most studies have tended to concentrate on the effects of passive smoking on the respiratory development of children, rather than investigate the consequences among adults. There are few estimates of the likely risk available. As an estimate, I have chosen to assume that the shape of the exposure-response equation is more like that observed for lung cancer than that for the cardiovascular system. As the risks for respiratory disease among active smokers are lower than the corresponding risks for lung cancer by a factor of about 2.5, I have assumed a risk of 1.10 for respiratory disease among passive smokers (cf for lung cancer among passive smokers). We estimate that there are about 3,000 male and 3,500 female deaths due to respiratory disease in Scotland every year (Table 3.7). 14

15 Table 3.7 Total number of respiratory disease deaths in Scotland by sex and smoking category Smoking category Relative risk Percentage of men in each smoking category group Men Number of respiratory deaths by smoking group Percentage of women in each smoking category group Women Number of respiratory deaths by smoking group Never 1 19% % 1, cigs/day % % cigs/day % 1,031 24% 1, cigs/day % 842 3% 226 Ex-smokers % 483 8% 231 Total deaths* 3,000 3,500 *This includes 1,439 male and 1,261 female respiratory deaths attributable to active smoking. Table 3.8 shows the distribution of the 297 male respiratory disease deaths and the 1,031 female respiratory disease deaths between lifelong non-smokers who have and who have not been exposed to ETS. In total there are 205 deaths amongst male and 791 deaths amongst female lifelong non-smokers exposed to ETS due to respiratory disease. Of these, 19 male respiratory disease deaths and 72 female respiratory disease deaths can be attributed to passive smoking. Table 3.8 Passive exposure Total number of respiratory disease deaths in lifelong non-smokers by ETS exposure category Relative risk Men Women Percentage of never smokers in each group Number of respiratory deaths by group Percentage of never smokers in each group Number of respiratory deaths by group No 1 33% 92 25% 240 Yes % % 791 P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 15

16 Table 3.9 summarises the estimated deaths from all four diseases attributable to active and passive smoking. In total, it is estimated that there are about 865 deaths per annum attributable to passive smoking. Table 3.9 Summary of number of deaths (four causes) attributable to active and passive smoking Cause of death Deaths Total Lung cancer 4,000 (2,300/1,700)** IHD 11,700 (6,200/5,500) Stroke 6,750 (2,500/4,250) Respiratory 6,500 (3,000/3,500) Attributable to active smoking 3,123 (1,867/1,256) 3,767 (2,210/1,557) 1,540 (668/872) 2,700 (1,439/1,261) Attributable to passive smoking* 44 (12/32) 395 (109/286) 335 (57/278) 91 (19/72) Four causes combined 28,950 (14,000/14,950) 11,130 (6,184/4,946) 865 (197/668) *Among lifelong non-smokers; **(male deaths/female deaths). 16

17 4 Discussion Estimation of the number of deaths among adults in Scotland which are caused by exposure to second-hand smoke is not an exact science. Knowledge of the number of people in the population exposed to ETS, both currently and historically, is sparse. The risk estimates associated with even broad levels of exposure have had to be based on international studies. Most of these relate to risks among lifelong non-smokers, as the literature concerning ex-smokers is virtually non-existent. The level of risk experienced in Scotland is a combination of the proportion of the population exposed and the magnitude of the exposure. In particular, the magnitude of exposure refers to that built up over a lifetime. In that respect, we are lucky in Scotland to have studies with some measure of the proportion exposed historically, as this is probably the closest indicator of lifetime exposure we are likely to get. As knowledge about the risks of passive smoking became more widely disseminated in the 1980s and 1990s, there has undoubtedly been a change in the way in which some smokers smoke when in the presence of non-smokers. This will make it difficult to assess more recent ETS exposure. However, current consequences in terms of the major chronic diseases will be much more a function of what happened some years ago in terms of ETS exposure. Our estimate of around deaths per year (among lifelong non-smokers) relates to deaths that have occurred since It relates to the four causes of death most strongly linked to smoking. Other causes of death have been linked to active smoking and it is plausible that there will be some small additional contribution from these other causes. Passive smoking represents the greatest risk to public health when compared to other forms of involuntary environmental exposure. A number of assumptions have had to be made. These include both the active and passive distributions of smoking historically in Scotland, the magnitude of the relative risks for each of the diseases considered and the latencies for the different diseases. While the assumptions used have not been ideal, they are genuine observations and it is unlikely that better information relating to the appropriate time period will become available. Sensitivity analysis has been undertaken (see appendix) to investigate how reliant the final estimates are on the assumptions made. It is reassuring to observe that the estimates produced under different assumptions lie within a range of about 10% (from 850 to 950 deaths per year). We have chosen to use the more conservative estimate. P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 17

18 This paper has concentrated on the impact of ETS exposure among lifelong nonsmokers. With a substantial number of smokers quitting over the years since the first reports on the harm of active smoking in the 1950s/1960s, there will be a significant risk from passive smoking amongst the ex-smoking group. However, the information required to provide a realistic estimate of their contribution to passive smoking deaths, is virtually nil. We need to know the pattern of ETS exposure among ex-smokers it is clear from the data from the Renfrew/Paisley co-habitees study that smokers who live with non-smokers are more likely to quit smoking and hence their domestic exposure would be minimal. Also it is not known to what extent smokers who live together might also quit smoking together. There is also the issue of how long it takes for the risk of the main smoking-related diseases for the former smokers to wash out, i.e. risk to return to approximately that of the lifelong non-smoker. Until the risk associated with active smoking can be considered to have returned to a non-smoking level, it is virtually impossible to prescribe a risk associated with passive smoking. For lung cancer, this wash-out time is of the order of 25 years whilst for the vascular causes it is considerably shorter (about 5 years). There are no studies that have looked at the risk of exsmokers for the main causes of death due to ETS. The current trends show that ex-smoking rates among men are considerably higher than they were in the 1970s and that the rates are moderately higher among women. This implies that there are a substantial number of ex-smokers at risk from ETS exposure. While difficult to quantify, there would appear to be as many exsmoking men and women exposed to ETS as there are lifelong non-smokers and may well be more. On this basis, given that the main contribution to deaths related to ETS exposure comes from the vascular causes and they are the causes which have short wash-out times, then we could be looking at a similar number of ETSrelated deaths among ex-smokers as we estimate for lifelong non-smokers. What impact would a ban on smoking in the workplace have on the number of deaths caused by passive smoking? This would depend on how successful the ban was and how much of an impact it would have on the total ETS exposure for an individual. As a rough guide, a 50% reduction in the average ETS exposure could be expected to deliver a 50% reduction in the number of attributable deaths over time. One area on which this report does not comment is the impact the introduction of a ban on smoking in the workplace might have on active smoking rates. Well over 10,000 deaths per year in Scotland can be attributed to active smoking and even small reductions in the active smoking rates will be hugely beneficial. The consequences of such a ban should be assessed not only in terms of the number of ETS-related deaths prevented but also its likely impact on active smoking rates in Scotland. 18

19 Key references Bonita, R.J., Duncan, J., Truelsen, T., Jackson, R.T. and Beaglehole, R. (1999) Passive smoking as well as active smoking increases the risk of acute stroke, Tobacco Control, 8, Brennan, P., Buffler, P.A., Reynolds, P., Wu, A.H., Wichmann, H.E., Agudo, A., Pershagen, G., Jockel, K.H., Benhamou, S., Greenberg, R.S., Merletti, F., Winck, C., Fontham, E.T., Kreuzer, M., Darby, S.C., Forastière, F., Simonato, L. and Boffetta, P. (2004) Secondhand smoke exposure in adulthood and risk of lung cancer among never smokers: a pooled analysis of two large studies, International Journal of Cancer, 109, Iribarren, C., Darbinian, J., Klatsky, A.L. and Friedman, G.D. (2004) Cohort study of exposure to environmental tobacco smoke and risk of first ischemic stroke and transient ischemic attack, Neuroepidemiology, 23, Law, M.R. and Hackshaw, A.K. (1996) Environmental tobacco smoke, British Medical Bulletin, 52, Law, M.R., Morris, J.K. and Wald, N.J. (1997) Environmental tobacco smoke exposure and ischaemic heart disease: an evaluation of the evidence, BMJ, 315, Wald, N. and Ritchie, C. (1984) Validation of studies on lung cancer in non-smokers married to smokers, Lancet, 1, Whincup, P.H., Gilg, J.A., Emberson, J.R., Jarvis, M.J., Feyerabend, C., Bryant, A., Walker, M. and Cook, D.G. (2004) Passive smoking and risk of coronary heart disease and stroke: prospective study with cotinine measurement, BMJ, 329, Woodward, A. and Laugesen, M. (2001) How many deaths are caused by second hand cigarette smoke? Tobacco Control, 10, P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 19

20 Appendix Sensitivity analyses A number of assumptions have been made in order to estimate the impact of exposure to ETS on the number of associated causes of death currently occurring in Scotland among adults. This appendix examines the impact of using alternative assumptions on the total numbers of deaths which can be considered to be associated with passive smoking. Three alternatives are considered. Using smoking prevalence data derived from the Scottish Heart Health Study conducted between 1984 and Using relative risks for active smoking and lung cancer which are an average of those derived from the Renfrew/Paisley study and the UK Doctors Study. Allowing the vascular causes of death to have a shorter latency in terms of disease progression to that assumed for the respiratory causes. Different smoking prevalence data The distribution of active cigarette smoking has been taken from the Renfrew/ Paisley survey. Whilst this is appropriate in that it represents a time period which is relevant to the development of the chronic diseases studied and it is a general population survey, it may not represent the pattern of active smoking in Scotland at that time. Judging by the lung cancer standardised mortality rate (SMR) for Renfrew local government district for the second half of the 1980s, the mortality rate for lung cancer was about 12% higher than that for Scotland as a whole. Similar excesses are apparent for IHD and stroke. The calculations for the four causes of death have been reworked (Table A1) using the distribution of cigarette smoking as measured by the Scottish Heart Health Survey (SHHS). The main differences as compared to the Renfrew/Paisley survey were: a greater percentage of lifelong non-smokers among men (27% vs. 19%) a lower percentage of lifelong non-smokers among women (42% vs. 46%) a higher percentage of ex-smokers among men (34% vs. 24%) a higher percentage of ex-smokers among women (20% vs. 8%) 20

21 Table A1 Estimated deaths using alternative smoking prevalence data Cause of death Total deaths Attributable to active smoking Attributable to passive smoking* Lung cancer 4,000 (2,300/1,700)** IHD 11,700 (6,200/5,500) Stroke 6,750 (2,500/4,250) Respiratory 6,500 (3,000/3,500) Four causes combined 28,950 (14,000/14,950) 2,943 (1,734/1,209) 3,303 (1,845/1,458) 1,217 (484/733) 2,325 (1,176/1,149) 9,788 (5,239/4,549) 55 (22/33) 437 (169/268) 353 (89/264) 100 (31/69) 945 (311/634) *Among lifelong non-smokers; **(male deaths/female deaths). This calculation produced an estimate of 945 deaths attributed to passive smoking among lifelong non-smokers (compared with 865 deaths calculated from Renfrew/ Paisley estimates, an increase of about 9%). Different relative risks for active smoking and lung cancer The relative risks for lung cancer in the West of Scotland are low compared to most other studies of lung cancer and smoking. This is because the rate of lung cancer in lifelong non-smokers is higher than in most other studies. It is not clear exactly why this is so but asbestos exposure among shipyard and other workers is a strong factor in the West of Scotland and atmospheric pollution appears to influence lung cancer rates particularly in the Glasgow area. As an alternative analysis (Table A2), the relative risks are doubled for lung cancer (i.e. the rate of lung cancer among lifelong non-smokers for Scotland as a whole is assumed to be about half that seen in the Renfrew/Paisley survey). A 50% increase is also incorporated into the calculation for respiratory disease, but no alteration is made to the risks for IHD and stroke. Cigarette smoking data from the SHHS are used. P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 21

22 Table A2 Estimated deaths using alternative relative risk for active smoking and lung cancer Cause of death Total deaths Attributable to active smoking Attributable to passive smoking* Lung cancer 4,000 (2,300/1,700) IHD 11,700 (6,200/5,500) Stroke 6,750 (2,500/4,250) Respiratory 6,500 (3,000/3,500) Four causes combined 28,950 (14,000/14,950) *Among lifelong non-smokers; **(male deaths/female deaths). 3,446 (2,007/1,439) 3,303 (1,845/1,458) 1,217 (484/733) 2,955 (1,474/1,481) 10,921 (5,810/5,111) 28 (11/17) 437 (169/268) 353 (89/264) 85 (26/59) 903 (295/608) This produces an estimate of 903 deaths, compared with 945 deaths under the earlier assumptions and 865 deaths in the original calculation. Allowing different latencies for vascular and respiratory causes of death A third possibility is to assume that the latencies for lung cancer and respiratory disease are different from deaths due to vascular causes (IHD, stroke). Using direct evidence on length of latencies and indirect evidence on the length of time it takes for the risk for a quitter to return to that of a lifelong non-smoker, it can be inferred that the latency for lung cancer and respiratory disease is of the order of years, but that for the vascular causes is much shorter (5 10 years). Applying these assumptions to the Scottish situation leads to an estimate of 925 deaths associated with exposure to second-hand smoke (compared to previous estimates of 865, 945 and 903 deaths) (Table A.3). 22

23 Table A3 Estimated deaths assuming different latencies for vascular and respiratory deaths Cause of death Total deaths Attributable to active smoking Attributable to passive smoking* Lung cancer 4,000 (2,300/1,700)** IHD 11,700 (6,200/5,500) Stroke 6,750 (2,500/4,250) Respiratory 6,500 (3,000/3,500) 3,123 (1,867/1,256) 3,303 (1,845/1,458) 1,217 (484/733) 2,700 (1,439/1261) 44 (12/32) 437 (169/268) 353 (89/264) 91 (19/72) Four causes combined 28,950 (14,000/14,950) 10,343 (5,635/4,708) 925 (289/636) *Among lifelong non-smokers; **(male deaths/female deaths). P A S S I V E S M O K I N G A N D A S S O C I AT E D C A U S E S O F D E AT H I N A D U LT S I N S C O T L A N D 23

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