Tobacco Documents Online

Smoking and Health 1964-1979 T H E C 0~ KT I N U I N G C 0 N T R 0 V E R S Y T H E T 0 B A C C 0 I N S T I T U T E 1776 K Street, N.W., Washington, D.C. 20006 January 10, 1979

Women and Smoking After two decades of denouncing smoking and claiming "proof" that cigarettes cause various diseases and disorders in men, anti-smoking organizations have in recent years launched special campaigns to persuade women that they, too, are ad- versely affected by cigarettes. Their alarums usually begin with the charge that the woman who smokes in pregnancy may harm her infant. There are claims, too, of reported increases in lung cancer mortality in women as a result of their smoking. Because of this new emphasis on the ladies, we devote a Inconsistent findings from studies of smoking women and their children make it impossible to draw con- vincing conclusions from the data. chapter here to what HEW has called "the smoking-related problems unique to women" (1) -- and a look at some of the unexplainable lung cancer mortality trends for women. Pregnancy Outcome A sizable section of the HEW 1977-78 report to Con- gress on smoking and health'(1) was devoted to smoking women Q C.7 and their pregnancies. It concluded with the strong language Q that cigarette smoking was "probably causally associated" CCjjlN QD 47

C with higher late fetal and infant mortality. However, the 2 actual data mainly relied upon by the HEW authors in reaching this conclusion suggest that any relationship between maternal smoking and pregnancy outcome is far from clear and any claims of causality have highly questionable foundation. The study relied upon by HEW in that last report to Congress was a retrospective analysis at Johns Hopkins of 51,490 births recorded in 10 teaching hospitals in 1960 and 1961 (2). Data were collecte& on infant birth weight, infant mortality, prematurity and placental complications. The statistical analyses of the data on infant mortality indicated that a history of a previous pregnancy loss, the mother's hospital status (private or public patient -- a socioeconomic indicator) and a variable related to age and number of previous pregnancies had "greater effects" on perinatal mortality than maternal smoking level. In their analyses for prematurity and placental complications, the researchers found that previous pregnancy loss and hospital pay status were more strongly related to unfavorable outcomes than maternal smoking level. The reported importance of previous pregnancy history and hospital pay status strongly indicates that a mother's pregnancy experience may well be determined by who the mother is -- her constitution or innate characteristics -- rather than whether or not she smokes. The complexity of all of 48

these findings and the areas to which the data point for further research seem strikingly inconsistent with the unswerv- ing and exclusive emphasis on the mother's smoking habits. Low-Birth-WeiRht Babies Like most other pregnancy studies, the work at Johns Ropkins found that smoking women on average have smaller infants than nonsmokers -- more of what are called low-birth- weight (LBW) babies. LBW infants weigh 2,500 grams -- about 5.5 pounds -- or less. Why and how this happens has not been explained. But the possibility that a common factor predisposes women both to smoke and to have a higher proportion of LBW infants was recently described by the director of a child health study who suggested that "the smoker and not the smoking" may determine whether a woman has an LBW infant (3). Dr. Bea van den Berg took over direction of the large PHS- funded California study from the late Dr. Jacob Yerushalmy, who first proposed, as early as 1964, the hypothesis that a mother's smoking may serve as a marker for -- but not as a causal factor in -- the birth of LBW infants (4). Yerushalmy contended that ineffective randomization and the problem of self-selection in studies comparing smoking and nonsmoking mothers made it difficult to draw any infer- ences from the observation that smokers seem to have more LBW infants (5). In perhaps his best-known study, he identi- 49

fied a group of women who began to smoke after their first children were born (6). Comparing the birth weights of chil- dren born before and after the women began smoking, he dis- covered that both groups of children were lighter than the children of nonsmoking mothers. He said this indicated some women will have smaller infants whether or not they smoke. Two reseachers published data in 1977 that appear to support Yerushalmy's hypothesis. A National Institutes of Health epidemiologist found that differences in mean birth weights of infants born to women who smoked during one pre- gnancy but not another were "more consistent with the self- selection hypothesis" than the causal hypothesis (7). An Australian who worked with records of 1,200 maternity patients concluded his findings were "compatible" with the theory that maternal smoking does not cause LBW but is "an index" of some other factor or factors (8). Perinatal Mortality Any claim that maternal smoking during pregnancy is causally related to increased perinatal mortality is not supported by the scientific evidence. Yerushalmy, for example, found that the mortality rate of LBW infants was considerably lower for those with smoking mothers than for those with nonsmoking mothers (9). He -contended that his data argued against the proposition that cigarette smoking acts as an external factor that interferes with fetal development. 50

In 1978, the editor of the British journal, Public Health, wrote that evidence that small infants of smoking mothers do not share the high mortality of infants of the same weight born to nonsmoking mothers "has been disregarded." He suggested, "We may tell women that if they smoke their baby may be small. But [we] should not claim risk to life" (10). Spontaneous Abortion In the 1973 HEW report to Congress, the last specifi- cally to discuss spontaneous abortion, the authors said several studies had reported finding a significantly higher, dose- related incidence among cigarette smokers. But they conceded that "the lack of control of significant variables other than cigarette smoking does not permit a firm conclusion to be drawn about the nature of the relationship" (11). No firm conclusion about the "nature" of the rela- tionship can be drawn now, either. A recent study by New York researchers did assert that smoking is "a risk factor" for spontaneous abortion (12). However, the researchers found no statistically significant relationship between the amount smoked and the rates of spon- O taneous abortion. Koreover,{their, emphasis on certain data in ~ ~. the study was criticized by another researcher, who said this co tW f ocus magnif ied "the apparent ef f ect of smoking" in the higher- tJ 51

He suggested that if some of the women were smoking "because they were uptight about a floundering pregnancy" that fact "might distort the picture just enough to make it appear that It ` risk age groups -- the younger and older mothers-to-be (13). smoking is an etiologic agent of spontaneous abortion, when in fact it may merely be a more prevalent behavior characteristic in a troubled pregnancy." Failure to consider this and a number of other factors caused him to conclude, he said, that "we are still at a loss for,the cause of spontaneous abortion." That smoking is a risk factor for spontaneous abortion is not supported by other studies, which have failed to show any significant link with smoking. These include two published since 1976 (14, 15). Another, conducted in Sweden, examined a variable that is not always considered. It found that an overall increased risk of spontaneous 0% abortion among smoking women was almost completely due to the fact the pregnancy was unwanted (16). that A British Medical Journal editorial of less than a year ago puts the reported relationship in perspective more succinctly than anything we coul&say: What remains to be established is whether the association between cigarette smoking and spon- taneous abortion is causal...Only by identifying a mechanism by which cigarette smoking could give rise to spontaneous abortion could we be confident of a causal relation (17). 52

Congenital Malformation .&t A physician appearing before an American Cancer Society "forum" on smokin~g stirred the audience with his charge that smoking is "likely to cause birth defects" (18). However, his opinion was not shared by another physician, appearing at a similar ACS "forum" two weeks later. The second doctor said: ...I don't think anyone has identified absolute evidence that this Jcongenital malformationj is a result of the chronic or even~ acute smoking of the mother (19). These conflicting opinions, especially within one anti-smoking organization, reflect the inconclusive scientific findings in this area. Several large-scale population studies have failed to establish a relationship between smoking and congenital malfor- mation (9, 15, 20, 21). Another, examining congenital mal- formation diagnosed during the first five years of life, found that fewer such conditions occurred in children born to women who smoked during pregnancy than to women who never smoked or to women wh~o stopped at some time before becoming pregnant (22). Even the New York researchers who reported an association between smoking and spontaneous abortion concluded, after study of the scientific literature on smoking and infant malforma- 53

tion, "it is unlikely that smoking acts to cause fetal anoma- lies" (12). That emotionalism can override objective analysis in any area of pregnancy and childbirth is illustrated by the headlines which accompanied the release of a study by a'Pitts- burgh pathologist who claimed maternal smoking was related to congenital malformation (23). Although one headline read "Baby Brain Defect Linked to Smoking" (24), examination of the research paper revealed that the pathologist had described this finding only as an "apparent association" that "requires further analysis." This sort of proviso, of course, never appears in headlines. Child Development Another favorite claim of anti-smokers is that smoking during pregnancy retards the subsequent growth and learning ability of the child. In fact, HEW Secretary Califano in early 1978 spoke of the "developmentally disabled" children of smoking mothers (25). The basis for these allegations? Apparently it is data from an on-going perinatal and child follow-up study in Britain which indicated that-the children of smoking mothers lagged behind the children of nonsmoking mothers in physical and mental development (26-28). The authors did note that the 54

effect of smoking during pregnancy is "relatively small" in comparison with the effects of some other factors, such as social class and the number of older and younger children the household (28). in In the British study, the children of smoking mothers were on the average 1 centimeter -- or only about three-tenths of an inch -- shorter than children of nonsmoking mothers (26). There was also a four-month difference in reading ability between the two groups of children (27). But analysis of physical growth showed that a number of other factors were associated with size at age 7. For example, the child of a blue-collar family was on the average 1.3 centimeters shorter than the child of wealthier parents, while the fourth-born child was usually 2.3 centimeters shorter than the first-born. In a later report from the same British study, researchers examined the children at age 11 and measured only minor differences in either height or mental development of children born to smoking and nonsmoking mothers (28). They also reported that these differences were less than the effects of some of the other factors considered. For instance, the difference between a child from a household with no older children and one from a household with three or more was, on the average, 16 months for;general ability, 29 months for w .~ reading, 14 months for mathematics, and 4 centimeters for ~ height. W 0~ 55