Exposure period is as important as the dose of exposure
Based on Figure 1 in the article[1], it could be inferred that the
timing of dust exposure would be crucial when investigating whether “Dust
exposure” would increase the risk of IHD among patients who already had
Respiratory diseases: The dust exposure of most interest would be the
exposure after the occurrence of the respiratory dise...
Exposure period is as important as the dose of exposure
Based on Figure 1 in the article[1], it could be inferred that the
timing of dust exposure would be crucial when investigating whether “Dust
exposure” would increase the risk of IHD among patients who already had
Respiratory diseases: The dust exposure of most interest would be the
exposure after the occurrence of the respiratory diseases. However people
who were already diagnosed with respiratory disease especially those in
more serious conditions were more likely to be moved away from the
cohorts, therefore a great part of dust exposure among people with chronic
respiratory diseases were likely to happen before the diagnosis of the
respiratory diseases, may appear to have minimum direct effect on IHD.
Smoking: a rope
Moreover smoking as a great risk factor for both respiratory disease
and IHD, but this study only treat smoke habits as a categorical
variable[1], it is far from enough, for example only among subjects who
are current smokers, people who have higher dose of exposure on tobacco
smoke are more likely to have both respiratory disease as well as IHD.
However an analysis only include life long non-smokers may reduce the
shadow of bias in the picture. Furthermore it is unrealistic to measure
the effect of interaction between smoking and aspiratory disease on
incidence of IHD based on the assessments of exposures in this study.
Reference
1. Koskela R-S, M.p., Sorsa J-A, Klockars M, Respiratory disease and
cardiovascular morbidity. Occup. Environ, 2005. 62.
In their paper entitled “Risk of lymphatic or haematopoietic cancer
mortality with occupational exposure to animals or the public”, Svec et.
al.[1] clearly imply that they believe mortality is an acceptable
surrogate for incidence of haematological malignancy in this study group.
Although they offer certain caveats regarding this approach, they ignore
the greatest potential confounder. Patients with...
In their paper entitled “Risk of lymphatic or haematopoietic cancer
mortality with occupational exposure to animals or the public”, Svec et.
al.[1] clearly imply that they believe mortality is an acceptable
surrogate for incidence of haematological malignancy in this study group.
Although they offer certain caveats regarding this approach, they ignore
the greatest potential confounder. Patients with haematological
malignancies are, by virtue of their disease, therapy or both, very likely
to be immunocompromised, often severely. As a consequence of this
immunoparesis, these patients may be expected to be much more vulnerable
to zoonotic infections and patients with occupational contact with animals
will be much more frequently exposed to such infections than patients with
other occupations.
To validate the use of mortality as a surrogate for incidence in this
cohort, it is necessary to rule out differential mortality from infection
between cases and controls affected by haematological malignancy. There is
no evidence in this paper that Svec et. al. have considered this potential
confounding factor. Absent such consideration, it is not possible to draw
any causal inference between occupations involving animal exposure and the
risk of developing a lympho-haemopoeitic malignancy as opposed to the risk
of dying from such a condition. A further analysis would be required
considering the proximate cause of death, rather than just the underlying
cause.
Yours sincerely,
Kenneth Campbell MSc (Clinical Oncology)
Reference List
1. Svec MA, Ward MH, Dosemeci M, Checkaway H, De Roos AJ. Risk of
lymphatic or haematopoietic cancer mortality with occupational exposure to
animals or the public. Occup Environ Med 2005;62:726-35.
Dear Editor
Exposure period is as important as the dose of exposure
Based on Figure 1 in the article[1], it could be inferred that the timing of dust exposure would be crucial when investigating whether “Dust exposure” would increase the risk of IHD among patients who already had Respiratory diseases: The dust exposure of most interest would be the exposure after the occurrence of the respiratory dise...
Dear Editor,
In their paper entitled “Risk of lymphatic or haematopoietic cancer mortality with occupational exposure to animals or the public”, Svec et. al.[1] clearly imply that they believe mortality is an acceptable surrogate for incidence of haematological malignancy in this study group. Although they offer certain caveats regarding this approach, they ignore the greatest potential confounder. Patients with...
Pages