Passive Smoking and Lung Cancer: A Reanalysis of Hirayama’s Data

Abstract

The statistical association between environmental tobacco smoke and lung cancer is controversial. The Hirayama Study seems to provide sound epidemiological evidence supporting this hypothesis. In a recent paper [6] I have analyzed the published studies. Regarding the Hirayama study the following facts have to be kept in mind:

• The study was not designed to test the hypothesis, whether passive smoking is associated with lung cancer or not. It can therefore only generate this hypothesis, not prove it.

• The cohort was not representative for the population of Japan. A selection bias is possible.

• The exposure indicator — the fact of being married to a man who smokes — is not reliable, not valid and not specific.

• The event indicator — dying on lung cancer as noted on death certificates — is neither reliable nor valid.

• Various confounding factors — for instance exposure at the working place, indoor air pollution, overall air pollution, type of medical care — were not accounted for.

• Bias in registering the fact, that a woman is a nonsmoker, was not controlled. Resulting differential misclassifications of the cases, who were smokers and had to be excluded, have not been considered.

• Almost nothing is known about the 200 cases. No case reports are available, autopsy and histology arc available in only 11.5%.