This study examines the association between tobacco smoking and the risk of bladder cancer in men and women. The research, conducted using data from the NIH-AARP cohort, found that current smokers had a significantly higher risk of bladder cancer compared to never smokers. Former smokers also showed elevated risk, with current smokers having a hazard ratio (HR) of 4.06 and former smokers an HR of 2.22. The population attributable risk (PAR) for ever smoking was 50% in men and 52% in women. These findings suggest that smoking remains a major risk factor for bladder cancer, with the risk being higher in the more recent NIH-AARP cohort compared to previous studies. The study also found that the risk estimates for current smoking in seven previous studies were lower, at 2.94, indicating that the association between smoking and bladder cancer has strengthened over time. The study highlights that changes in cigarette composition may contribute to this increased risk. Additionally, the study notes that the prevalence of smoking is similar in men and women in the United States, which may explain why the PAR for smoking is comparable in both sexes. The study also found that the risk of bladder cancer is higher in men than in women, with men having approximately 3.71 times the risk of women. The study concludes that tobacco smoking is a strong risk factor for bladder cancer, with PARs of approximately 50% in both men and women. The findings support the hypothesis that the risk of bladder cancer associated with cigarette smoking has increased over time in the United States, possibly due to changes in cigarette composition. Prevention efforts should continue to focus on reducing the prevalence of cigarette smoking.This study examines the association between tobacco smoking and the risk of bladder cancer in men and women. The research, conducted using data from the NIH-AARP cohort, found that current smokers had a significantly higher risk of bladder cancer compared to never smokers. Former smokers also showed elevated risk, with current smokers having a hazard ratio (HR) of 4.06 and former smokers an HR of 2.22. The population attributable risk (PAR) for ever smoking was 50% in men and 52% in women. These findings suggest that smoking remains a major risk factor for bladder cancer, with the risk being higher in the more recent NIH-AARP cohort compared to previous studies. The study also found that the risk estimates for current smoking in seven previous studies were lower, at 2.94, indicating that the association between smoking and bladder cancer has strengthened over time. The study highlights that changes in cigarette composition may contribute to this increased risk. Additionally, the study notes that the prevalence of smoking is similar in men and women in the United States, which may explain why the PAR for smoking is comparable in both sexes. The study also found that the risk of bladder cancer is higher in men than in women, with men having approximately 3.71 times the risk of women. The study concludes that tobacco smoking is a strong risk factor for bladder cancer, with PARs of approximately 50% in both men and women. The findings support the hypothesis that the risk of bladder cancer associated with cigarette smoking has increased over time in the United States, possibly due to changes in cigarette composition. Prevention efforts should continue to focus on reducing the prevalence of cigarette smoking.