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Monday, December 8, 2025
TRONDHEIM, NORWAY – High cardiorespiratory fitness may be a potent shield against urinary tract cancers, particularly in men, according to a landmark study released this week in Scientific Reports.
The research, which followed nearly 47,000 adults for over two decades, offers some of the most compelling evidence to date that physical fitness is not just a tool for heart health, but a critical factor in cancer prevention. The study found that individuals with high estimated cardiorespiratory fitness (eCRF) had a 36% lower risk of developing urinary tract cancers—including bladder and kidney cancer—compared to their least fit peers.
“These findings provide a clear signal that cardiorespiratory fitness is a modifiable risk factor with significant protective potential,” said Dr. Youssef Khalil, the study’s lead author and a researcher at the Norwegian University of Science and Technology (NTNU). “What is particularly encouraging is that this protection is observable even when fitness is estimated through non-exercise models, making it a practical metric for clinical settings.”
Key Findings: A Strong Protective Effect
The study analyzed data from 46,968 participants in the second Trøndelag Health Study (HUNT2), a massive population-based cohort in Norway. Researchers utilized a validated “non-exercise” model to estimate cardiorespiratory fitness, calculating eCRF based on age, waist circumference, resting heart rate, and self-reported physical activity levels.
Participants were categorized into low, medium, and high fitness groups and followed for a median of 22 years. The results revealed a stark “dose-response” relationship, where higher fitness levels correlated with lower cancer risk:
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Overall Reduction: Participants in the high-fitness group had a 36% lower risk of urinary tract cancers compared to the low-fitness group. Even those with medium fitness saw a 13% reduction.
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Men Benefit Most: The protective effect was strikingly pronounced in men. Highly fit men experienced a 41% lower risk of urinary tract cancers. Medium-fit men had a 17% lower risk.
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Kidney vs. Bladder Cancer: The study found a clear inverse relationship for kidney cancer: as fitness increased, risk decreased. For bladder cancer, high fitness was linked to a 34% lower risk in men, though no significant association was observed in women.
The “Non-Exercise” Advantage
One of the study’s most practical implications is its method of measuring fitness. Traditionally, accurate cardiorespiratory fitness testing requires a treadmill stress test (VO2 max test), which is expensive and impractical for routine primary care.
“By using a non-exercise model, this study demonstrates that physicians can identify high-risk patients using simple, readily available metrics like resting heart rate and waist circumference,” explained Dr. Elena Rossi, a urologic oncologist at the University of Zurich who was not involved in the study. “It shifts fitness from an abstract concept to a tangible clinical vital sign, much like blood pressure.”
Context: A Rising Health Burden
The publication of these findings comes at a critical time. According to the American Cancer Society’s 2025 projections, bladder cancer cases are expected to rise, with an estimated 84,870 new diagnoses in the United States alone this year. It remains the fourth most common cancer in men, yet prevention strategies have historically lagged behind those for lung or colorectal cancers.
“We have long known that smoking is a primary driver of bladder cancer,” noted Dr. Rossi. “However, identifying positive lifestyle factors—things patients can actively improve, rather than just avoid—is a psychological game-changer for prevention.”
Biological Mechanisms
While the study was observational and cannot definitively prove cause and effect, experts point to several biological mechanisms that could explain the link between fitness and reduced cancer risk. High cardiorespiratory fitness is often a marker for better immune system surveillance, reduced chronic inflammation, and improved insulin sensitivity.
“Fit individuals tend to have lower levels of circulating inflammatory markers and growth factors that can fuel tumor development,” said Dr. Yi-Qian Sun, a co-author of the study. “Furthermore, physical activity—the primary driver of fitness—helps regulate hormones and improves vascular health, which may specifically benefit the highly vascularized tissues of the kidneys and bladder.”
Limitations and Considerations
The study does have limitations. The distinct difference in results between men and women warrants further investigation. The authors suggest this could be due to hormonal differences or the fact that bladder cancer is significantly less common in women, reducing the statistical power to detect an effect. Additionally, because the study used estimated fitness rather than direct VO2 max measurements, there is a margin for error, though the large sample size mitigates this.
Implications for Public Health
For the average person, the message is empowering: you don’t need to run marathons to lower your risk. The “medium” fitness group—achievable for most people through brisk walking and moderate activity—still saw significant benefits.
“This reinforces the concept that exercise is medicine,” Dr. Khalil concluded. “Improving your cardiorespiratory fitness is one of the most effective investments you can make for your long-term health.”
Medical Disclaimer
Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.
References
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Primary Study: Khalil, Y., Sun, Y.-Q., & Mai, X. (2025). Nonexercise estimated cardiorespiratory fitness in relation to incidence of urinary tract, bladder and kidney cancer in the HUNT study. Scientific Reports. DOI: 10.1038/s41598-025-29410-7
