Global study finds bladder cancer risk linked to body size in men

Men with larger body size in adulthood, defined by body mass index (BMI), were up to 16% more likely to develop bladder cancer than those with a smaller body size, while no similar link was found in women, according to one of the largest studies of its kind out today (17 April 2026).

The study was funded by Wereld Kanker Onderzoek Fonds (WKOF) and led by Professor Roger Milne at the Cancer Council Victoria’s (Australia) Cancer Epidemiology Division. In the study, published today in the Journal of Clinical Oncology, the team analysed data from 30 long-running international studies, following 2,533,008 adults and recording 20,447 bladder cancer cases.

They found in men that bladder cancer risk rose as BMI increased. Compared with men in the healthy-weight range, men who were overweight had around an 8% higher risk of bladder cancer, and men with obesity around a 16% higher risk.

When the team looked at waist measurements, they found that a larger waist circumference measured at enrolment (typically mid-to-late adulthood) was also linked with higher risk of bladder cancer in men – each 10-centimetre increase in waist circumference was linked with around a 6% higher risk in men.

Prof Roger Milne, Head of Cancer Epidemiology at Cancer Council Victoria, said:

“Overweight and obesity have been convincingly linked to 13 types of cancer and we wanted to get clarity on the link between body size and bladder cancer. By pooling data from more than 2.5 million people, we are getting closer to finding the answers.

“Higher BMI and a larger waistline in adulthood were linked with higher bladder cancer risk in men. We also saw signals suggesting BMI early in adulthood may matter years later, which is an important area for future research.”

What is causing these differences?

Bladder cancer is far more common in men than women. Worldwide in 2022 there were 471,293 new cases in men compared with 143,005 in women (GLOBOCAN 2022).

In women, the study found little evidence overall that BMI or waist size measured at enrolment (typically mid-to-late adulthood) was linked with bladder cancer risk.

As with all observational research, the study identifies associations and cannot by itself prove that body size causes bladder cancer.

The team suggests the difference results for men and women in this study may partly relate to how body fat is stored and how it affects the body. Men tend to carry more fat around the abdominal organs (often described as “visceral fat”), which is more metabolically active and linked with inflammation and insulin-related changes, while women tend to store a higher proportion of fat under the skin (“subcutaneous fat”).

Dr Nina Afshar, Research Fellow at Cancer Council Victoria, said:

“Carrying extra weight affects the body in several ways that increase cancer risk. It can change hormones, cause chronic inflammation, and trigger other processes that encourage abnormal cell growth. We want to better understand how these processes contribute to bladder cancer risk and call for future research to investigate the underlying mechanisms.”

The researchers carefully accounted for smoking history, the strongest established preventable risk factor for bladder cancer. Smoking remains a major driver of risk, but the findings suggest that maintaining a healthy weight and avoiding excess abdominal fat may also be relevant for prevention – particularly for men.

Investigating early life risk

However, when researchers looked earlier in life (between the ages of 18 and 21), they found that having a BMI of 25 or above was associated with a higher risk of bladder cancer later on in both men and women.

The researchers note this early adulthood finding should be interpreted with some caution, particularly for women, because the number of cases in the group that recorded the highest early-adulthood BMI was smaller. Further studies are needed to help shed light on the changing bladder cancer risk across the lifespan as well as to better understand how early factors influence bladder cancer risk later in life.

Dr Giota Mitrou, World Cancer Research Fund International’s Executive Director of Research and Policy, said:

“This is one of the biggest studies to date to better understand whether body size may be linked to bladder cancer. By funding and bringing together evidence at this scale, we can move beyond mixed results from smaller studies and give clearer, more reliable answers about bladder cancer prevention globally.

“This study strengthens the evidence that, alongside not smoking and avoiding occupational exposure to bladder carcinogens, maintaining a healthy weight – and avoiding excess abdominal fat in particular – may help reduce bladder cancer risk, especially for men. It also opens up important questions about how body size in early-adulthood may shape cancer risk later in life.”