REVIEW 674 CONFIDENTIAL Subiect ref 8d "The decrease in severity of aszr-ma in children of parents who smoke since the parents have been ex.--Dsing them to less cigarette smoke" A B Murray and B J Morrison Journal of Allergy and Clinical Immunology (1993), 91, 102-10 This paper collected infor-mation including parental smoking, severity of asthma, lung functien (FEV 1 and FEF 25-75% ), and bronchial responsiveness to histamine (PC 20 ) from 807 non-smoking children with asthma referred to a Vancouver cli=c between 1983 and 1990. Comparisons were made of the 415 children admitted before July 1986, and the 392 children admitted afterwards. Doczors referring patients to the clinic have, since 1985, been urged to counsel parents of asthmatic children never to smoke when in the home. The main findings of the study were as follows: (i) Although the total number of cigarettes smoked by mothers and by fathers was similar for the two periods, there was a highly significant drop in the number of cigarettes reported to be smoked in the presence of the child, from 7 to 3 for the mother, and from 5 to 2 for the father. (ii) Where the mother was a smoker, there was a highly s~gnificant decline in the asthma score and increase in the two indices of lung U1 function between the two periods. In contrast, where the mother was C) a non-smoker, there was no decline in asthma score, and a smaller CO 00 N; BATCo document for Legal Services: Health Canada 19 OctoberI 999 increase in lung E%t, to paternal sm,:)I-in;; significant. (iii) The number of cigaret-~-4-i --o in :.Iie of the child by the motb,--r child's asthma score function (negative). were also signific.-n-a- ~-.r (L-.r) Adjustment for se4, L;z- , ---v! cf ::-z- relationships noted in ( ") .1 - - n - fo r ri b e 4 .. . - iz .- , -.I:- -- 7~ -, of cigarettes smoked by t`.c t;ano. r--oir as r::.;: child reduced the significance oE The authors conclude that "thc-r- is increasing awareness of the sfff-:cL~ has caused parents to smoke fewer ci. 5 t-.- .4 -- t 1 "1 t,~ - ,nr7 a t I c children, and that the resulting cit with a marked improvement in tl-,e of astl, ~a of the s:::o*,.ers' children who have been referred to our In considering the results from. should be made: (a) CO in expired air was used to check tts- ;:rULII-- '.~-.CSS -.f the children's statements that thay ~,ere non-smcke,-s. Se-.-%-.i ch-;1,.::un who admitted to being smokers were ..i- st:udy' )u,,. n-) further smokers were detected bv zn- n t:V useful marker of ETS exposure. 7L is LiIaL 01. U11 (Z) 00 GN Co (IN. cz., (-11 BATCo document for Legal Services: Health Canada 19 October 1999 -3- urine samples were not tall-er for cotinine analys1s to allow objective correlation with the indices of asth.--a and lung function. (b) Smoking habits of the parents were usually provided only by the mother and were unvalidated. Is it not possible that at least part of the reported reduction in smoking in the presence of the child by the parents may have resulted from increasing denial? After all, there is abundant evidence in the literature that people advised by their doctor to give up smoking frequently falsely admit that they have done so. A similar scenario seems likely to exist if, as here, the doctor advised parents not to smoke in the presence of the child. (C) The study showed no real evidence at all that bronchial hyper-responsiveness, as measured by the PC 20 test, was associated with smoking by the parents or that it decreased between the two periods. Other studies have reported differences in bronchial responsiveness in children according to the parents' smoking, suggesting that ETS might cause asthma through an allergic mechanism. The results of this study seem inconsistent with this explanation. (d) The study included all patients, new and old, referred to the clinic over the period in question. Given that new patients would have had very much less time than old patients to act on the advice (if given) not to smoke in front of their children. it is very surprising that the authors made no attempt to separate out the new and old patients in analysis. U1 (e) Data on a reasonably extensive range of variables associated with asthma were collected and compared between the two time periods, 00 C1% co C) BATCo document for Legal Services : Health Canada 19 October 1999 with no significant differences seen. However it is possiDle that other var4ables not recorded mig!,t have been in part respons-Ke for the change over time in asthma score and lung function, e.g. exposure to arborne allergens, difference in use of drugs. (f) Inspecting tl~he detailed results in Table IIA a striking fact emerges, name'-.1 that though in the first period the mean asthma score was hig*.-.-.y significantly (p<0.001) higher if the mother smoked (mean 8.2 S.E. 0.3) than if the mother did not smoke (mean 5.4 S.E. 0.2), in the second period the mean asthma score was actually quite highly significantly (p<0.01) lower if the mother smoked (mean 5.8 S.E. 0.2) thar. if the mother did not smoke (mean 6.6 S.---. 0.2). The authors co=pletely fail to mention this point, which seems inconsistent vith their thesis. (g) Finally, and ---ery importantly, if one studies Table IV and compares the results under column 2 and column 3. one can com?ute the following differences between the two time periods (where the parent smokes): Unadjusted for adjusted for _ cigarettes cigarettes Asch---& score -0.99 -1.02 FEV 1 % +14.5 +11,4 FEF 25%-75% +14.7 +11.95 It can be seen that in fact only a very small proportion of the difference in recorded response between the two time per-ods (and nothing at all as regards asthma) can be explained by the parents smoking less --n front of their children- This is in direct contrast to the authors' claims. Although there has been a marked improvement CD C) 00 C1\ C~ V1 BATCo document for Legal Services : Health Canada 19 October 1999 -5- in asthma score and lung function over the period in children of smokers, it anDears to be mainly -due to reasons other Chan reduce smoking bv the Darents in the child's Presence. It is notable in Table 11L -that t7ne:e are quite substantial improvements in lung function (though -.~t in asthma score) over the time period in children whose parents do not smoke. Generally, the pa;er is unconvincing. and parts of the data inconsistent wizin t~he authors' hypothesis are nor. really brought to the reader's attenzion. P N Lee 11.11.93 ui C) CD CN Co CI', BATCo document for Legal Services : Health Canada 19 October 1999 M