The researchers used various statistical models to analyse the association between the years since quitting smoking and the risk of bladder cancer.
For the study, the researchers 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.
The study found that 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.
“Although bladder cancer is a fairly rare cancer type, representing an estimated 4.6 per cent of new cancer cases in 2019, it is the most common malignancy of the urinary system, with high recurrence rate and significant mortality,” said Yueyao Li, Ph.D candidate from the School of Public Health, Indiana University in Bloomington, US.
“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,” Li added.
Published in the journal Cancer Prevention Research, the study 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.
“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,” said Li.