The role of smoking in explaining racial/ethnic disparities in bladder cancer incidence in the United States.

Introduction: Smoking is the most important modifiable risk factor for bladder cancer (BC), with the odds of developing BC among current and former smokers 3 times higher than never-smokers. We hypothesized that the observed disparities in BC incidence may be partially attributable to differences in smoking prevalence. We examined the attributable risk of BC related to smoking according to race/ethnicity and sex.

Material And Methods: We used data from SEER and the Behavioral Risk Factor Surveillance System to estimate BC cases that would have been prevented if current and former smokers had never smoked to calculate the Population Attributable Fractions, stratified by sex and race/ethnicity. SDs of BC incidences across racial/ethnic groups before and after smoking elimination were calculated to estimate disparities.

Results: A total of 25,747 cases of BC were analyzed from 21 registries in 2018. By removing smoking, 10,176 cases (40%) would have been eliminated. Smoking was associated with a higher proportion of BC cases among males (42%) than females (36%). Across racial/ethnic groups, smoking contributed to the highest proportion of BC cases among American Indian/Alaska Natives (AI/AN) (43%) and Whites (36%) for females, and highest among AI/ANs (47%) and Blacks (44%) for males. Removing smoking, the SD of BC incidence across racial/ethnic groups was reduced for females (39%) and males (44%).

Conclusion: Approximately 40% of cases of BC in the United States are attributable to smoking, with the highest proportion in AI/ANs for both males and females, and the lowest in Hispanics for females and Asians and Pacific Islanders for males. Smoking contributes to almost half of racial/ethnic disparities in BC incidence in the United States. Accordingly, health policy to encourage smoking cessation among racial-ethnic minorities may substantially reduce inequalities in BC incidence.