The findings, published today in the Journal of the National Cancer Institute, showwomen are more likely to contract the main types of lung cancer than men at every level of exposure to cigarette smoke. "This gender difference cannot be explained by differences in baseline exposure, smoking history or body size; it is likely due to women's higher susceptibility to tobacco carcinogens," said the co-author of the study, Dr Stephen Lam, of the University of British Columbia, Canada.
Smoking causes about 120,000 deaths in the UK every year - or one in five of all deaths. The latest government figures show that in 1996 nearly 36,000 people died from lung cancer caused by smoking. The number of women dying this way has more than doubled in the past 23 years, from 6,961 in 1973 to 13,062 in 1996. There has been a decrease in male victims during the same period, from 29,463 to 22,852.
Previous British research has shown that nearly twice as many women as men under 65 are diagnosed with small-cell lung cancer, the most dangerous form of the disease. Experts believed that the differences between men and women could be explained by women smoking in a different way to men, taking shorter, sharper inhalations or inhaling more deeply because they are more likely to buy "light" cigarettes. However, the new research shows the outer lung cells of women are more susceptible to tobacco carcinogens.
Dr Mike Pearson, a spokesman for the British Thoracic Society, said: "This is another step to understanding the gender differences. There is definitely a genetic factor involved because only a proportion of men and women who smoke are susceptible to cancer. It is perfectly possible this genetic factor can also explain some of the differences between the sexes. Women's lungs are also smaller, which means they get more particle deposits."
The study of 400 men and women who had been smoking a pack a day for 20 years also found that the traditional way lung cancer is detected, by measuring breathing difficulty, was not suitable for women. The findings showed women developed more cancers in the outer parts of the lung, which does not have such an effect on breathing ability, while men were more likely to develop cancer in the large central airways.
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