Smoking not only increases the risk of bladder cancer, it also affects the course of the disease, with heavier smokers more likely to develop aggressive forms, a new study suggests.

Over 400 people are newly diagnosed with cancer of the bladder every year in Ireland.

According to US scientists, it is already known that smoking is one of the most common causes of the disease. However until now, it was unclear whether the habit affected its progression.

The scientists studied the bladder tumours and smoking history of 212 patients affected by the disease. They found that people who smoked the most tended to develop the most aggressive and deadly forms of the cancer compared to people who never smoked or who smoked less.

"The link between smoking intensity and prognosis found in this study points to the incrementally harmful effects of smoking," the US team said.

Details of these findings are published in the medical journal, Cancer.