Larger body size is linked to a higher risk of bladder cancer in men but not in women, found a pooled analysis of more than 2.5 million adults across 30 international studies published recently in the Journal of Clinical Oncology.
The authors said these findings suggest that preventing obesity, along with reducing smoking and workplace exposures to carcinogens, could help lower bladder cancer rates worldwide.
Researchers analyzed data from 2,533,008 participants, including 1,025,547 men and 1,507,461 women, followed for a median of eight to 29 years. During that time, 20,447 people developed bladder cancer, including 15,259 men and 5,188 women. This study evaluated body mass index, waist circumference and height while accounting for smoking and other risk factors.
Among men, excess weight was consistently associated with increased risk. Compared with a normal BMI of 18.5 to 24.9 kg/m2, overweight men had an 8% higher chance of developing bladder cancer, and those with obesity had a 16% higher chance. Each 5 kg/m2 increase in BMI raised risk by 7%. Larger waist size also mattered, with a 6% higher risk for every 10 cm increase. Taller height showed a similar pattern, with risk increasing modestly as height rose.
Read more about causes and risk factors of bladder cancer
In contrast, women did not show a clear link between body size and bladder cancer risk; increases in BMI or waist circumference were not associated with meaningful changes in risk. These differences between men and women were consistent across regions and were not explained by smoking habits.
“Although BMI does not capture central adiposity, waist circumference results also showed no association among females, indicating that BMI’s measurement limitations alone are unlikely to explain lack of association in females,” explained the study’s authors.
Some nuances emerged. In early adulthood, higher BMI was associated with increased bladder cancer risk in both sexes, suggesting that weight earlier in life may play a role. However, in mid to later adulthood, the association remained strong only in men. Results were stable across multiple sensitivity analyses and population subgroups.
For patients, these findings highlight that body weight may be an important and modifiable risk factor for men. Maintaining a healthy weight, quitting smoking and limiting exposure to harmful chemicals at work may reduce the likelihood of developing bladder cancer. For women, traditional risk factors such as smoking remain more central, though maintaining overall health is still important.
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