Cancer risk up in Japanese women exposed to smoke

NEW YORK (Reuters Health) - The results of a study published in the International Journal of Cancer confirm that passive smoking is a risk factor for lung cancer, especially adenocarcinoma, among non-smoking Japanese women.

"Although smoking is a major cause of lung cancer, the proportion of lung cancer cases among Japanese women who never smoked is high," Dr. Norie Kurahashi, of the National Cancer Center, Tokyo, and colleagues write. "As the prevalence of smoking in Japan is relatively high in men, but low in women, the development of lung cancer in non-smoking Japanese women may be significantly impacted by passive smoking."

In a population-based study, the researchers examined the association between a husband's smoking and the lung cancer risk in his non-smoking wife. The authors also assessed the association between passive smoking from other sources -- at the workplace or during childhood -- in women with lung cancer who never smoked.

A total of 109 cases of lung cancer were diagnosed among 28,414 lifelong non-smoking women over an average follow-up of 13.3 years. Of these women, 82 developed adenocarcinoma.

Overall, 49 percent of the women were exposed to passive smoking from husbands who were current smokers. Compared with women married to men who never smoked, those married to current smokers had a 34 percent increased risk of all types of lung cancer.

Passive smoking from husbands who were current smokers was associated with a statistically significant two-fold increased risk of lung adenocarcinoma.

Passive smoking in the workplace also increased the risk of all lung cancers by 32 percent and the risk of adenocarcinoma by 16 percent.

No association was observed between passive smoking in childhood and lung cancer risk.

These findings are supported by the mechanism of sidestream smoke through the nasal passages, which shows that the volatile components of sidestream smoke are more likely to reach the outer portions of the lungs compared with mainstream smoke, Kurahashi and colleagues point out.

"Particularly in Japan, where room sizes tend to be small and living conditions congested, sidestream smoke may be directly transmitted to non-smoking women before dilution by room air," they add.

SOURCE: International Journal of Cancer, February 2008.