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ANiJIICAN JOURNAL or ErIDLNioLOGY Vol. 1'27iNo..5Geqyrisat O 1988' by T6e Johns Hopkin. Univer.ay School 'of Hygi.ae and Public Health Prin+ad in U.S.A. Allirighu reservad Original Contributions HEART DISEASE MORTALITY IN NONSMOKERS LIVING WITH SMOKERS r K J. HELSING: ' D. P. SANDLER,'' G. W. COMSTOCK.' rwD E. CHEE' Fieliing, K. J. (The Johns Hopkins Training Center for Public Health Research, Hagerstown, MD 21740), D., P. Sandler, G. W. Comstock, and E. Chee. Heart disease mortality in nortsmokers living with smokers. Am 1 Epldentlol' 1988;127:915-22. A private census of Washington County, Maryland, in 1963 obtained knforrtnation on smoking habits of all adults in the census, and death certificates of ati residents who died in the next 12 years were coded for underlying cause of death and matched to the census. Among the white population aged 25 and over, 4,162 men and 14,673 women had never smoked. Jn this group,, death cates han arteriosclerotic heart disease were significantlyy higher among men (relative Ask (RR) = 1.31, 95% confidence Interval (CI) 1.1-1.6) and women (RR = 1.24, 95% Cl 1.1-1.4) who ived' with smokers in 1963, after adjustment for age, martbl status, years of schooling, and quality of housing. Among women, tfie relative risk increased significantly (p < 0.005) with increasing level of exposure; among men, there was tittle evidence of a dose-response reiation: The relative risks for aiortamokers who lived with smokers were greatest among both men and women who were younger than age 45 in 1963, but the number of deaths in these groups was small, and confidence intervais were broad. These results suggest a em.M but measurable risk for arteriosclerotic heart dissase among nonsmokers who live with smokersL heart diseases; smoking; tobacco smoke pollution The association of cigarette smoking with arteriosclerotic heart' disease deaths is well-known (1), and it is now increasingly suspected that the presence of smoke in the Received'for publication May 26, 1987, and in final form September 3f1; 1987. ' Department of E.bidemioloey„The Johns Hopkins University Sc6oo1 of Hygiene and Public Health, B1d+ timore„MD. ' EbidemioloQy Branch, N'ational Institute of Et- vironmental Health Sciencea, Research Ttiangk Paric, NC: Reprint requesta to Dr. Knud J. Helain` The Jomns Hopkins Training Center for Public Health Researca. Washiagton County Health Department, P.O. Bo: 2067, Hagerstown.,MD 21740: This work was supported in part by' Contract 65?548 from the National iInstitute of Environmental Healtt Sciences and by Research Career Award IiL21760 from the National Heart, Lung, and Blood Institute. Data available at the Johns Hopkins Train- i-q Cender for Public Health Research in Haterstos9n, M0; made tliis study possible. -environment may pose a risk to non- w smokers. Evidence on the possible associa- tion of what' is called passive smoking with arteriosclerotic heart disease is as yet far from conclusive, and both the Surgeon General's recent report (2) and that of the National Research Counciliof the National Academy of Sciences (3) emphasize the need for additional studies. As pointed out by the Surgeon General, because heart dis, ease is so prevalent, even a small increase in risk associated with passive smoking could have a substantial public bealth im- pact. Some epidemiologic studies have been conducted concerning the possible associa- tion of arteriosclerotic heart disease with passive smoking. A recent case-control' study by Lee et al. (4) reported no consis- tent evidence of greater passive smoke e:- 915

I 916 KELSnNc gr AL posure among 118 hospitalized nonsmoking cases than among nonsmoking controls hospitalized for reasons considered unre- lated to smoking. Gillis et al. (5) reported results of up to 10 years of follow-up for 8,128 Scottish adults aged 45-64 years who participated in a multiphasic health screen- ing exam and for whom smoking history of a spouse or partner was known. At the initial examination, nonsmoking women who lived with smokers had slightly more cardiovascular symptoms such as angina or abnormal electrocardiogram than non- smokers who were not ezposed, No such excess was reported for men. At follow-up, death rates from myocardial infarction for nonsmoking men and women married to smokers were midway between rates for nonezposed~ and' those for active smokers. The number of observed deaths was small, and differences were not statistically aig- nificant. Garland et al. (6, 7): reported a dose-response relation in women aged 50- 79 years between the amount their hus- bands smoked and death rates from isch- emic heart disease„ but the number of deaths was small, and~ the differences were less than statistically significant, despite a relative risk of 2.7. Hirayama (8) ~ reported in his 15-year prospective study, that there was a significantly higher risk of ischemic heartt disease among Japanese women whose husbands smoked as compared with those whose husbands did not smoke, as well as a significant dose-response relationn with amount' smoked. Svendsen et al. (9), in the Multiple Risk Factor Intervention Trial prospective study, found that non- smoking men whose wives smoked had roughly twice the risk of coronary heart disease morbidity and mortality compared with those whose wives did not smoke. Of particular interest is their finding of no difference between the two groups in blood pressure or cholesterol levels. Data from a private census conducted in 1963 and other records available in Wash- ington County, Maryland, were used to evaluate the heart disease risk associated with household smoke exposure among nonsmoking adults. The results of this 12- year follow-up study are reported here. MATERiALS AND METHODS In July 1963; a private census obtained data on an estimated 98' per cent of the households in Washington County, Mary. land. Information included sex, age, race, marital status, years of schooling, and housing characteristics for all 91,909 iuidi- vidtsals enumerated. Information on ciga- rette, cigar, and pipe smoking habits as well as frequency of church attendance was re- corded for each household member aged 161/i or older as of July 15, 1963: A follow- up of a 5 per cent sample of the households in the 1963 census was conducted in 1971 in order to assess the probability of still living in Washington County after, eight years. Since age, marital'status,, years of schooling, and frequency of church atten- dance were the only characteristics that showed aignificant' association with re- maining in the county, a probability of re- maining in the county was calculated for each adult in the census aged 25 and over based on those factors and was entered on the census tape. These probabilities allow the population remaining in the county to be estimated at any point in the eight-year period. Since only about 2 per cent of the noninstitutionalized 1963 population was black, the present study is confined to whites. A1l death certificates of Washington County residents who died between July 1963 and July 1975 have been coded as to primary, contributing, and underlying causes of death without knowledge of cen- sus data, and the information was entered on the census tape for decedents who were in the 1963 census. The Seventh Revision of the Irsternational CltrasWication of Dis- eases (1CD) (10) was used for coding causes of death; for this study, we used only deaths with underlying causes of death classified as arteriosclerotic heart' disease including coronary disease (ICD 420) and other myo- cardial degeneration (ICD 422); We algo analyzed deaths for which arteriosclerotic V

PASSIVE SMOKING AND ARTERR'>9CL8ROTtC HEART DISEASE 917 heart disease was listed on the death certif- icate but not coded as the underlying cause of death to confirm that simiiar associa- tions were observed. The category, other myocardial degeneration was included be-' cause many physicians in this community refer to deaths due to coronary artery dis- ease as arteriosclerotic cardiovascular dis- ease, which is classified under ICD 422. For the current study, all adults were assigned smoking contribution scores (ta- ble 1) ranging from 0~ to 12 based on their reported smoking histories-never smoked, present or ex-smoker of cigarettes, cigars, or pipe, and amount smoked. In general, current smokers were assigned scores that were twice those of ex-smokers of like amount. The only exception to this was for persons who only smoked a pipe and/or cigars; census data did not distinguish be- tween current or past pipe or cigar smokers. When~pipe and/or cigar smokers also cur- rently smoked cigarettes, however,, they were assume& to be current pipe and/or cigar smokers. The contribution to house- hold exposure of only pipe and/or cigar smoke was treated as less than that of current smokers of fewer than 10 cigarettes. Although the household exposure from a pipe or cigar may equal or exceed that from a cigarette, it was arbitrarily assumed that't cigar or pipe smokers who never smoked cigarettes would;, in general, smoke fewer pipes or cigars per day than~light cigarette smokers: Only 9 per cent of spouses of nonsmoking females smoked only pipes and/or cigars. Thus, the impact of this ar- bitrary ranking of pipe and cigar smokers and current light smokers is not likely to be large. A household exposure score was calculated as the sum of the contributions of all persons living in that household, and each person's passive smoke exposure score is the household score minus his or her awn contribution to it. A housing index (ranging from 0 to 10) based on running water, number of bath- rooms, type of heating system, cooking fuel, and availability of telephone is a rough indicator of quality of housing. In the ab- sence of solid data on household income,, the housing index acts as a surrogate mea- sure, particularly to identify the very low- income households. Among the 22,9?3 white men and 25,369 white women aged 25 and over in the 1963 census, 4,162 men and 14,873 women re- ported that they had never smoked. The calculated 1969 midpoint nem ining popu- lation of these nonsmokera, based on the 1971 follow-up, was 3,454 men and 12,345 women; these constitute the population of interest for this study. Death rates were calculated as deaths in 12 years per 1,000 midpoint population, adjusted for age, housing quality, marital ststus, andyears of schooling by the binary variable multiple regression procedure de- scribed by Feldstein (11) and adapted for epidemiologic use by Shah and Abbey (12). TAas.t 1 RESULTS CaFculation of eochperaon's concr;baaon to smoi<e Table 2 shows the characteristics of the exposure in the horne Washington Cbtmty'white population aged Ea• Current 25 and older oriei.nallv listed in the 1963 -- ~"-'- emok.r ®oker census and the percea tagR in each category Never smoked 0 0 reporting that they had never smoked. As Cisus and/or pipe onW 1 1 was characteristic of that' period, relatively CtIXTettee . <10/day 1 2 10-20/day 9 s 2i+/d,y 6 lo If c4ars and/or pipe in addition ~to ciearettes. add 1 2 ' Ceeuus data did not d'utin`uisb between e:- and eumnt pipe or cigar smoken. few men but more than half the women had never smoked. Among men, there was a slight tendency for the better educated to have a higher percentage of nonsmokers, a trend opposite to that among women. Characteristics of the population of in- terest for this study, those who never

918 AE1snaG Sr AL T.at.e 2 Pnsm+tqge d onvi+nl eenn.s poyulation who reponed they hod weuer.mohed, by demqgrOic eharoeterisda; whitu aged t25 years,, Worhington County. MDi 1963 lilto women cbmectensuc No. S never l~.dol~.d ® o No % Ot~Tt ®oked Tota1 22.973. 18.1 25,369 58.6 Age (3,eu+) 26-44 10,928' 16:6 11,652 46:7 45-54 5,104 16:1 6,378 53.3 55-61 3,631 17.2 4,001 70.1 65+ 3,310 27.6 4,338 86.6 Muit.1 sutut Married 19,699 17:4, 18,704' 55.4 Other 3,274' 22.4 6,665 67:6 Grades of whool completed (1.-8• 9,977 19.1 9,929 68:5 9-11 4,527 13:1 5,497 52.4 12 5,256 19.1 6,802 54.4 13+ 3,213 20.4 3,141 47:6 Hmuin` mde: 0-7 4,591 15.9: 012 59.9: 8-10 18.382 78.7 20;857 58.4 * 1ucl{Ides parLiclpants for wboID grades of scbool'cAmpleLld :w'16 not known. smoked, are listed, in table 3, which shows the calculated midpoint populations in 1969!and the percentage of each group e=- pose& to tobacco smoked by others in the household. For both men and women, the percentage ezposed'to environmental smoke in the home tends to drop with in- creasing age and with higher quality of housing. There is,however„a sex difference in the association of education with per- centage exposed, nonsmoking men showing slightly increased exposure with more years of schooling and nonsmoking women show- ing a slight trend in the opposite direction. In addition, married men are less likely and married women more likely to be exposed to the smoke of others in the home. Table 4 shows the adjusted rates of death from arteriosclerotic heart disease (ICD 420 and 422) in the 12-year period 1963- 1975 among men and women who never smoked, according to their level of passive smoke exposure at home. The overall rates are adjusted for age, quality of housi.ng,, marital status, and years of schooling. For .men, the relative risk for those with some household exposure compared .vith tbe none:posed is statistically significant (rel- ative risk (RR) = 1.31, 95 per cent confi- dence interval, (CI) 1.1-1.6); but the trend with increasing exposure is negligible. For women, both the difference between the expose& and nonexposed (RR = 1.24, 95 _ per cent CI: 1.1-1.4) and the trend of in- g creasing mortality with increasing levels of ezposure in the home (Cochran chi-square = 9.2, p< U':005) are atatistically signifi- oant. The balance of table 4 presents the adjusted arteriosclerotic heart disease mor- tality rates for each age group by level of. smoke exposure at home. The age group 25-44 years shows the highest relative riekss for both men and womenj but because of the very small numbers, the 95 per cent confidence limits are quite broad. Never- theless, it is worthy of note that seven of Zhe eight age-sex groups show increased siak of arteriosclerotic heartt disease deaths. .vith passive smoke exposure in the home, and f ve of the eight indicate a trend with increasing level of exposure. Results have been sbown only for heart disease deaths that were classified as un- derlying cause of death. Although not 

PASSIVE SMOKING AND ARTERIOSCLEROTIC HEART D1SEA3E 919 TAs[.e 3 DiKribution of midpoint population o/Toiiiw qBed L7B rcare who neuer rmokad, by scz,,pererntqp espo.ed to smoiee at home, and'demoBraphic charncteristia, Washington County, JKD, 1963-1975 Men woman C6uaer.ristic Na x spo..d in the Lomr Na % ezFa.d in the bome 3,454 29.5 12,345 66S A4e (yrus) in 1963 25-44 1,502 30.0 4,618 72.0 45^54 731 34.3 2,553 72.1 55-64 554 28.2 2,472 82.8 65+ 667 24.4 2,702 5fl:5 Marital isttt~u Married 2.929 27:2 9,033 75.7 Other 525 42.7 3,312 37.5 Gr.des of school completed 0-8' 1,578 27:0 5,589' 62.7 9-11 604' 29.4 2,455 70.0 : 12 862 31.7 3,158' 68.6 13+ 510 34:1 1,143' 60.6 Housing index 0-7 594 33.7 2,238 68.2 6-10 2,860 28.7 10,107 64.9 • Includes partieipanta for whom grades of school completad was not know n. shown, death rates and relative risks were also calculated for heart disease deathss coded as a primary cause or a contributing cause of death. A total of 461, nonsmokingg men and 1,281 nonsmoking women had arteriosclerotic heart disease listed on the death certificate. ©f these, 80 per cent of men land 77 per cent of women were consid- ered to have heart'disease as the underlying cause of death. Results were similar whether or not heart disease was considered by the nosologist to be the underlying cause of death. For example, the adjusted relative risk among exposed nonsmoking women compared with nonexposed women was 1.2 for heart disease listed anywhere on the death certiFcate and 1.1 when heart disease was on the death certificate but not consid- ered to be the underlying cause of death. For males, the corresponding relative risks were 1.3 and 1.4. DiscussioN The findings of this study tend to con- firm those of Hirayama (8), whose relative risk from ischemic heartt disease was 1.3 for nonsmoking women married to smokers; our relative risks, however, are consider- ably lower than those of Garland et al. (7) ~ and Svendsen et al. (9) and higher than those of Lee et al. (4). There are a number of strengths in this study. Information on smoking was col- lected for each person in 1963, and follow- up procedures were the same for everyone. Some potential biases were thus avoided: those involved in asking people (or their family members) ~ about prior smoking hab- its after an illness or death, when recall may be colored by an unconscious search for any possible cause of the illness, and those involved in selecting controls from hospital populations. Furthermore, smok- ing histories were recorded prior to publi- cation in 1964 of the Surgeon General's first report on smoking and health (13) and the subsequent increase in concern about smoking. Obviously, the home is not the only place where nonsmokers may be exposed to to- bacco smoke. Any association of household passive smoke exposure with heart disease mortality may, in this study, appear weaker than the actual association to the extent

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PASSIVE SMOKING AND ARTERIOSCLEROZ7C HEART DISEASE 921 that some of those presumed to have zero or moderate exposure at home were actually subjectedto moderate or heavy passive smoke at work or elgewhere outside the home. In this population and during the years of the study, among women aged 25 and over, about 50 per cent were nonwork- ing housewives who would be less likely to be exposed to tobacco smoke outside thee home than men, the vast majority of whom were employed This may in part explain the greater consistency over age groups among women than among men in the in- crease in relative risk with indicated level ofezposure. A11 smoking data were obtained in the 1963 census, so no provision can be made for changes in smoking habits which we know took place as a result of publicity about health effects of smoking. Data from a 1975 private census replicating the 1963 census show that the percentage of current cigarette smokers in~ the 40- to 49-year age range, for example, dropped from 78 per cent to 44 per cent among men and from 50 per cent to 36 per cent among women. On the whole, then, our household passive smoke exposure scores based on 1963 cen- sua data will tend to be higher than the actual exposures in later years and to that eztent may exaggerate the amount of ex- posure required to match with a given risk of deathfrom arteriosclerotic heart disease. We also have no data on changes in the household composition which may have oc- curre& prior to or after 1963. Thus, we implicitly assume that any such changes occurred randomly in the population. We have very little data on other risk factors for arteriosclerotic heart disease in the study population. We have tried to ad- just for some: smoking, by restricting the study to nonsmokers; age and sex, by as- sessing the risk separately for eight age-sex groups;'and housing quality, marital status, and years of schooling, by binary variable multiple adjustment. A fumal' check by mul~ tiple logistic and Poisson regression adjust- ment gave virtually identical! results. Two other studies encourage us to disregard hy- pertension and cholesterol' as possible con- founding factors. The Garland et al. (6, 7) study showed no significant differences in systolic blood pressure, obesity index, and plasma cholesterol between women married to present or e=-smokers and those married to men who never smoked. Sim'iLarly, the Svendsen et al. (9) study showed no signif- icant difference in blood pressure and serum cholesterol between men whose wives smoked and those whose wives were nonsmokers. However, other factors such as diet and exercise might differ in families with and without smokers; we cannot ig- nore the possibility that such differences could influence our findings. :In summary, this 12-year study of a non- smoking population of white men and women aged 25 and over suggests that non- smokers who live with smokers are at a higher risk of death from arteriosclerotic heart disease than those who live with non- amokers. It seems reasonable to suppose that tobacco smoke is a factor in the in- creased risk. RETERSNCEB 1. US Department', of Health and Human Servioes. The health consequences of smolcint-cardiovas- cular disease: a report: of the Surgeon General! Washington, DC: US GPO, 1983. (DHHS publi- cation no. (PHS)84-50204). 2. US Department of Health and Human Services. T6e health consequences of involuntary smokin~ a report of the Surgeon General. Washington+DC: US GPO,1986. (DHHS publication no. (CDC)87- 8398): 3. National Research Council. Environmental to• baeco smoke-measuring ezposuees and aseessinj health effects. Wi..hincton, DC: National Acad- emy Press, 1986. 4. Lee PN,,Chamberlain J, Alderson MR. Relation. ship of passive smoking to riik of htna cancer and other smoking-aasociated di.eese. Br J Cannr 1986;64:97-105. 6. Gillis CR, Hole DJ, Hewthorne VM, et aL Effect of environmental tobacco smoke in two urban oommunities in the west of Scotlaad. Eur J R.spir Die 1981;65(Sappl 133):121-6. 6. Garland C, Barrett-Connor E, Svaraz T4 et eL Effects of passive smoking on ischemic beert dir ease mortality of non.mokera: a prospective study. Am J Epidemiol 1985;121:64,5-50. 7. Garland C. F.rr.tum Am J Epidemiol 1985;

922 IiE1SIhIG ET AL. 12't1112 & Hie.xama T. Pa.aive ®okin` a new target of epidemioiogy. J Fsp Gia Med 1985;10:287-93. 9. Svendaen KH. KW1er 1., Naaton J. ff.fiects of yarive smoking in the Multiyle Risk Factor In, tervention Ttial. American Haart Association 58th Scientific Snaiona,1985: 10: Wor1d' Health Organization. Manual of the mter- national'statistical eL.dSeation of di..a.e, iskju- ries and e.u.en of death. Vol 1. Based on the raeommendationa of the seventh r.vision oonfer- .nce,1955. Geneva. S..itserland, 1957: 11. F.Id.tsin MS. A binary variable multiple se;re.- aion mat6od of analyzing factors affecting peri- natal mortality and other outooma of pr.gaancy. J R Stat Soc 1966;129:61-73. I2 Shab Fl{, Abbey H. Effects of some factors on neonatal and yo.t-neonatal mortality. Milbank Mem Fund Q 1971;49:33-57: 13. US Department of Health, F.dueation and Wel- lare. Smoking and bsalth: a report of the advisory committee to the Surgeon General of the Public Health Servioe. Waahington, DC: US GP0.1964. (DHEW publication no. (PHS)1103).