Women smokers face a higher risk of bladder cancer than previously thought, according to a US study out that points to the changing content of cigarettes as a potential reason for the increase.

The latest data shows that smoking is responsible for about half of bladder cancer cases in women, compared to previous studies that showed between 20-30 per cent of such cases were attributable to tobacco use.

“The stronger association between smoking and bladder cancer is possibly due to changes in cigarette composition or smoking habits over the years,” said study author Neal Freedman of the National Cancer Institute.

The research, funded by the US National Institutes of Health and published in the Journal of the American Medical Association, said “the composition of cigarettes has changed during the past 50 years”.

These changes have led to “a reduction in tar and nicotine concentrations in cigarette smoke, but also to an apparent increase in the concentration of specific carcinogens, including beta-napthylamine, a known bladder carcinogen.”

Also, more women are smoking than before, which could explain the change.

“Men and women are about equally likely to smoke, as observed in the current study and in the US population overall, according to surveillance by Centres for Disease Control and Prevention,” said the study.

“The majority of the earlier studies were conducted at time periods or in geographic regions where smoking was much less common among women.”

Previous studies have shown the risk of bladder cancer in current and former smokers was between 50-65 per cent in men and 20-30 per cent in women, while current smokers face triple the risk of getting bladder cancer as people who never smoked. The study shows that smoking is linked to an even higher risk of bladder cancer in women – 52 per cent – while men stayed about the same at 50 per cent.