Critiques studies of childhood respiratory diseases and environmental tobacco smoke (ETS). Concludes "claims that parental smoking plays a causal role in the development of respiratory symptoms and reduced lung function in children are not scientifically justified." Includes 132 references; identical to Bates 2024196728.
Page 1: 2046663338
CHILDHOOD RESPIRATORY D~SEASE
Perhaps no claim regarding ETS is as capable of provoking
strong feelings as the charge that parents who smoke may harm the
health of their children. While the issue of parental smoking is
laden with emotion, the scientific basis for the claim is difficulZ
to interpret. For example, while one study examines respiratory
symptoms or illness such as coughs and colds by questionnaire
responses from parentsI, another measures lung function with
special equipment at a school or health facility.~ In the U.S.
alone, according to one report, this has led to a situation in
which studies of ETS and the respiratory system are "being carried
out by at least three different groups, are employing different
populations and methodologies and have led to varying
Perhaps not surprisingly, such studies, each with a
different sample size, data collection method, and analysis, tend
to yield factually incompatible and contrary conclusions. For
instance, although certain studies have reported adverse findings
between parental smoking and respiratory illness in children,~'4z or
invasive bacterial or viral infections~s'~9 others have observed no
significant reiationship.1'5°-66 After a five-year study of over 400
children, for example, a Dutch research group concluded there was
"no evidence" that parental smoking had an appreciable effect on
respiratory symptoms in school children.~z A similar conclusion was
Page 2: 2046663339
reached by a group of U.S. researchers, including a critic of
smoking, who found "no siqnificant relation" between parental
s~oking and respiratory symptoms in ~ study of nearly 400 families
with 816 children in three cities.5°
The contradictory nature of findings on the issue of
Page 3: 2046663340
confounding factors. The potential impact of such factors was
given special consideration in the report from a workshop on ~TS
sponsored by the U.S. National Instikutes of Health.~ After
listing numerous such factors, including types of heating used,
socio-economic status and demographic and medical characteristics
of the study population, the report cautioned "that any study which
ignores them will be seriously flawed."
The importance of such factors in evaluating the outcome
of research on parental smoking is supported by a number of reports
which have shown that the use of gas stoves in the home may be
independently associated with respiratory disease~°'5~,~9,9~-9~ and
impaired pulmonary performance9z'98 in children. One group of
British researchers acknowledged the possible influence of factors
such as cross-infection in the home and genetic susceptibility to
childhood respiratory illness and symptoms.~'~ More recently,
researchers in Hong Kong reported "a highly significant
correlation" between the frequency of respiratory illnesses of
mothers and their children.~ One study reported that children with
recurrent respiratory tract infections "tend to belong to £amilies
~ith health problems.''~ Maternal age has also now b~en recognized
as a possible f~ctor in childhood lower respiratory illness.TM
Page 4: 2046663341
Other confounding factors independent of parental smoking
have been reported recently in the literature. For example,
studies in the United Kingdom have identified damp housin~
and paternal occupation~6 as potential explanatory factors for the
occurrence o£ respiratory illness in children. Other recent
studies have identified outdoor air pollution,~°z-~1° infections
transmitted during day-care attendance~3'I~I°I~ decreased breast-
feeding,I~,~5 and the use of kerosene heaters and woodburning stoves
in the home and exposure to wood smoke outdoors~6"I~° as factors
related to childhood respiratory disease.
reactions in some
The relevance of dampness in the etiology of respiratory
symptoms in children is supported by current research which l~nks
dampness with the presence of molds, dust mites, fungi and other
allergenic microbes. The growth of fungi and molds in the home is
to respiratory symptoms and sensitization
individuals.~,~z~'~z~ Recent investigations
that sxposure to ETS does not increase
sensitization to common allergens in children.~25~2~ Exposure to
indoor sources of NO2 has also been associated with respiratory
symptoms and decreased pulmonary function in children.~'~s
others have conceded that the reliance of such studies on
questionnaires for information about respiratory symptoms casts
Page 5: 2046663342
doubt on their reported findings. In one study that reported a
significant association between parental smoking and respiratory
symptoms, for example, it was noted that even "slight changes~' in
the way the q~/estions were phrased could result "in substantial
differences in the type of responses one obtainso''~ similarly,
another study Observed that there was a s~gnificant difference in
the respiratory symptoms reported depending on which parent
completed the questionnaire.~ Authors of another study that
reported adverse effects of parental smoking on the respiratory
health of children conceded that "since the exposure variables used
in these analyses were subject to substantial measurement error, a
more refined measurement of personal exposure is required.''~9 One
researcher who is critical of parental smoking has stated that
"quantitative assessment of involuntary exposure of infants and
children to ETS has been very imprecise and probably inaccurate.''129
Studies util±zing seemingly more objective standards such
as actual measurements of lung function are also open to criticism.
Even reviewers of the literature who are critical of parental
smoking concede that the tests used in these studies are
"influenced by a large number of variabl~s.''13a They list age,
height, and gender of the test su~Dject as well as his or her
motivat±on, cooperation, and effort pu~ forth during the test, the
skill and experience of the operator, and the type of
Page 6: 2046663343
instrume~tat±on used as variables that can affect ~he results of
pulmonary function measurements. The reviewers explain that these
problems are especial.ly important in pulmonary function measures
taken in children. In 1989, two American co-researchers, Witorsch
and Witorsch, reported that "it has been shown that the mean
pulmonary performance within a sinqle group of children can vary
significantly from one spirometry test to the next without any
apparent cause" and that it "is noteworthy that such statistically
significant differences are similar in magnitude to most of the
small decrements in pulmonary function reported in children of
The shortcomings of studies analyzing the relationship
between ETS exposure and childhood health were highlighted in a
1988 report by two U.S. investigators who re-examined 30 such
studies and evaluated them for their scientific validity.~z They
noted that while several studies of adeq~/ate scientific design had
reported a statistically significant relationship between ETS
exposures and childhood health, "most studies had significant
design problems that prevent reliance on their conclusions." The
authors concluded that "many questions remain, and future studies
should consider important methodological standards to determine
more accurately the effect of passive smoking on child health."
Page 7: 2046663344
Thus, claims that parental smoking plays a causal role in
the development of respiratory symptoms and reduced lung function
in children are not scien:ifically justified. Such claims are
typically based upon a single study of a selected symptom (such as
cough or wheeze). These kinds of studies invariably fail to
consider nutrition, health habits of the family,, and other
l~festyle variables. Similarly, studies that report reduced lung
function in children of smoking parents fail to address the issue
of socio-economic status or the potential role of genetic and
family traits in pulmonary function capabilities,s5 Moreover, the
reductions reported in the literature are small and of uncertain
clinical or biological significance, and are contradicted by a
number of studies that reportedly have observed no effect of
parental smoking on children's lung function.
-- AN --
Page 8: 2046663345
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Lebowitz, M., Armet, D.B., and Knudson, R., "The Effect of
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U.S. Department of Health and Human Services, Public Health
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on Respiratory Effects of Involuntary Smoke Exposure:
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Cameron, P., and Robertson, D., "Effect of Home Envirorument
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-- AN --
Page 9: 2046663346
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Colley, 3., "Respiratory Symptoms in Chil'dren and Parental
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Page 10: 2046663347
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