Washington: Quitting cigarette smoking is associated with a significantly reduced risk of bladder cancer in postmenopausal women, suggests a study.
According to the research published in the journal ‘Cancer Prevention Research’, the most significant reduction in risk occurred in the first 10 years after quitting, with a modest but continued decline in later years.
“Smoking is a well-established risk factor for bladder cancer, but findings on the relationship between duration of smoking cessation and the reduction in bladder cancer risk are inconsistent,” said Yueyao Li, the study’s author.
She added that while bladder cancer is more common in men, women often have worse outcomes, even when diagnosed at similar stages.
“Our study emphasizes the importance of primary prevention (by not beginning to smoke) and secondary prevention (through smoking cessation) in the prevention of bladder cancer among postmenopausal women,” Li said. “Current smokers should be advised to quit smoking in order to reduce the risk of bladder cancer.”
In this study, Li and colleagues sought to analyze the dose-response relationship between time since quitting smoking and risk of bladder cancer among postmenopausal women and to investigate whether risk among former smokers ever normalised to the risk faced by those who never smoked.
The study included data from 143,279 women, all of whom had supplied information on whether they had ever smoked cigarettes, how much they had smoked, and whether they were current smokers. In all, 52.7 per cent of the women were categorised as “never smokers,” 40.2 per cent as former smokers, and 7.1 per cent as current smokers.
It showed that in comparison to never smokers, former smokers had twice the risk of bladder cancer, and current smokers had more than three times the risk.
They found that the steepest reduction in risk occurred in the first 10 years after quitting smoking, with a 25 per cent drop. The risk continued to decrease after 10 years of quitting, but even after 30 or more years since quitting smoking, the risk remained higher for women who had smoked than those who never did.
However, in time-updated models that reflected those who stopped smoking during the study period, the researchers found that compared with women who continued to smoke, those who quit smoking during the follow-up years had a 39 per cent decrease in bladder cancer risk, and the risk continued to decline over time.
Li said that while the biological mechanisms of the association between bladder cancer and smoking are not known, the study results indicate that women of any age should be discouraged from smoking, and even those who have smoked for many years stand to benefit from quitting.
Li cautioned that the study was based on postmenopausal women, so results may not be fully generalisable. Also, exposure to smoking was self-reported.