Women cigarette smokers have a higher risk of bladder cancer than previously reported. According to scientists from the National Cancer Institute, published in the Journal of the American Medical Association.

Bladder Cancer is a cancer that forms in the tissue of the bladder in the inner lining of the bladder. The cells that form squamous cell carcinoma and adenocarcinoma develop as a result of chronic irritation and inflammation. In 2011, estimated 69,250 people will be diagnosed with bladder cancer and 14,990 will die from the disease in the United States.

In a study using data from over half a million participants in the NIH AARP Diet and Health, Researchers found that in comparison to previous studies that has shown that only 20-30 percent of bladder cancer cases in the women were caused by smoking, new study data shows that smoking is responsible for about half of female bladder cancer cases, similar to the proportion found in men.

The increase in the proportion of cases among women may be the result of the increased amount of female smokers; overall both men and women are equally likely to smoke in the United States, according to the CDC.

The majority of earlier studies were conducted at the time when smoking was less common amongst women. Researchers found that risk by smoking is higher in this study than previously reported.

"Current smokers in our study had a fourfold excess risk of developing bladder cancer, compared to a threefold excess risk in previous studies. The stronger association between smoking and bladder cancer is possibly due to changes in cigarette composition or smoking habits over the years," said the study author Neal Freedman, Ph.D. in the Division of Cancer Epidemiology and Genetics (DCEG) in National Cancer Institute (NCI).

Researchers found that although there have been reductions in concentration of tar and nicotine in cigarettes, the concentration of certain carcinogens associated with bladder cancer has been increased.

In the current study, former smokers were twice as likely to develop bladder cancer compared to non smokers, smoking cessation was associated with reduced bladder cancer risk, and participants who have not smoked for over 10 years had a lower incidence of bladder cancer compared to those who quit earlier or are continually smoking.

"Our findings provide additional evidence of the importance of preventing smoking initiation and promoting cessation for both men and women," said senior author Christian Abnet, Ph.D., also from DCEG. "Although the prevalence of cigarette smoking has declined, about 20 percent of the U.S. adult population continues to smoke."