A LARGE Norwegian cohort study has found that adults with higher estimated cardiorespiratory fitness (eCRF) face a significantly lower risk of developing urinary tract cancers, including bladder and kidney cancer, over more than two decades of follow-up. The findings, drawn from 46,968 participants in the second Trøndelag Health Study (HUNT2), provide some of the strongest population-based evidence to date that better fitness may offer long-term protection against these cancers, particularly for men.
Researchers estimated each participant’s cardiorespiratory fitness using a validated model incorporating age, waist circumference, resting heart rate, and physical activity levels. Individuals were categorised into low (20%), medium (40%), or high (40%) eCRF groups, then followed for a median of 22.2 years to track cancer incidence. Cause-specific Cox proportional hazard models were used to assess cancer risk.
Sex Differences in the Impact of Cardiorespiratory Fitness
Across the full cohort, participants with medium fitness had a 13% lower risk of urinary tract cancers compared with those in the low-fitness group, while those with high fitness saw a striking 36% reduction. The protective effect was even more pronounced in men: medium-fit men showed a 17% lower risk, and highly fit men experienced a 41% risk reduction.
When researchers examined cancer types individually, high eCRF was linked to a 34% lower risk of bladder cancer in men, but not in women, suggesting possible sex differences in how fitness affects bladder cancer development. For kidney cancer, the team observed a clear inverse dose-response relationship: as fitness increased, kidney cancer risk decreased, with the trend being especially strong among men.
Why Cardiorespiratory Fitness May Be a Useful Clinical Marker
Although the study is observational and cannot prove causation, the long follow-up period, large sample size, and consistent dose-response patterns strengthen the case for eCRF as a practical marker for evaluating the relationship between fitness and urinary tract cancer risk. The authors suggest that incorporating fitness assessments into routine health evaluations may help identify individuals at greater cancer risk and highlight the potential value of improving cardiorespiratory fitness through lifestyle changes.
Reference
Khalil Y et al. Nonexercise estimated cardiorespiratory fitness in relation to incidence of urinary tract, bladder and kidney cancer in the HUNT study. Sci Reo. 2025. doi: 10.1038/s41598-025-29410-7
